| 0.01 NPLC | 0.1 NPLC | 1 NPLC | 10 NPLC | 50 NPLC | 100 NPLC | 1000 NPLC | |
| 200mV | +11 | +10 | +7 | +3 | +4 | +5 | +9 |
| 2V | +11 | +10 | +7 | +2 | +4 | +5 | +9 |
| 20V | +11 | +10 | +1 | Primary | +4 | +5 | +5 |
| 200V | +11 | +10 | +8 | +6 | +8 | +9 | +9 |
| 1000V | +11 | +10 | +8 | +6 | +8 | +9 | +9 |
:SYST:AZER:TYPE SYNC; // Here we enable autozero sync
:SYST:LSYN:STAT ON; // Here enable line sync
:SENS:FUNC 'VOLT:DC'; // Measure voltage DCV
:SENS:VOLT:DC:NPLC 10; // Set NPLC to 10
:SENS:VOLT:DC:RANGE 2; // Set range manual to 2V
:SENS:VOLT:DC:DIG 8.5; // Set resolution to 8.5 digits
:SENS:VOLT:DC:AVER:STAT OFF; // Filter off
:TRIG:SEQ:SOUR TIM; // Set trigger source from timer
:TRIG:SEQ:DEL 1; // Set timer to 1 second
:READ? // Read data
:SYST:AZER:STAT ON; // Here enable autozero
:SYST:FAZ:STAT ON; // Here we enable front end autozero
:SYST:LSYN:STAT ON; // Here enable line sync
:SENS:FUNC 'VOLT:DC'; // Measure voltage DCV
:SENS:VOLT:CHAN1:LPAS:STAT OFF; // Analog filter off
:SENS:VOLT:CHAN1:DFIL:STAT OFF; // Digital filter off
:SENS:VOLT:CHAN1:NPLC 5; // Set NPLC to 5
:SENS:VOLT:CHAN1:RANG 10; // Set range manual to 10V
:SENS:VOLT:CHAN1:DIG 8.5; // Set resolution to 8.5 digits
:TRIG:SEQ:SOUR TIM; // Set trigger source from timer
:TRIG:SEQ:DEL 1; // Set timer to 1 second
:READ? // Read data
:SYST:AZER:TYPE SYNC; // Here we enable autozero sync
:SYST:LSYN:STAT ON; // Here enable line sync
:SENS:FUNC 'VOLT:DC'; // Measure voltage DCV
:SENS:VOLT:DC:NPLC 10; // Set NPLC to 10
:SENS:VOLT:DC:RANGE 2; // Set range manual to 2V
:SENS:VOLT:DC:DIG 8.5; // Set resolution to 8.5 digits
:SENS:VOLT:DC:AVER:STAT OFF; // Filter off
:TRIG:SEQ:SOUR TIM; // Set trigger source from timer
:TRIG:SEQ:DEL 1; // Set timer to 1 second
:READ? // Read data
:SYST:AZER:STAT ON; // Here enable autozero
:SYST:FAZ:STAT ON; // Here we enable front end autozero
:SYST:LSYN:STAT ON; // Here enable line sync
:SENS:FUNC 'VOLT:DC'; // Measure voltage DCV
:SENS:VOLT:CHAN1:LPAS:STAT OFF; // Analog filter off
:SENS:VOLT:CHAN1:DFIL:STAT OFF; // Digital filter off
:SENS:VOLT:CHAN1:NPLC 5; // Set NPLC to 5
:SENS:VOLT:CHAN1:RANG 10; // Set range manual to 10V
:SENS:VOLT:CHAN1:DIG 8.5; // Set resolution to 8.5 digits
:TRIG:SEQ:SOUR TIM; // Set trigger source from timer
:TRIG:SEQ:DEL 1; // Set timer to 1 second
:READ? // Read data
TiN,Please post your EZGPIB code here. I can help you to test and debug it, and provide output formatting if needed.
Do you have a sample CSV file for reference?
I think I have the 2K1 working in EZGPIB, I just need to save the results in a format that has all the needed fields.
1. Have to use interface to log data from meter, such as RS232 or GPIB/LAN.Why? I don't see the problem using the internal memory and then save it to file. (assuming you have enough memory)
Why? I don't see the problem using the internal memory and then save it to file. (assuming you have enough memory)That's fine too, I was just assuming that not much meters have USB interface to copy data. Keithley 2001/2002 for example don't have even RS232, only GPIB, even tho it can store data in NVRAM.
I am not sure how meaningful the data is without the shortage block.If you used fresh clean copper wire with good contact, it should be no visible difference.
I am also using a copper wire loop formed to fit across the two input terminals. The sense terminals are not used for voltage readings and I left them open.
If you used fresh clean copper wire with good contact, it should be no visible difference.
After you get shorting PCBs you could try that as well, if there will be any difference.
I will add new data to first post and page soon, was busy fixing another 2001 ;) Now I have three which can collect data for us.
I have been working with code for the 3458A and also reading the programming commands. I have run across a minor setting that NANDBlog should try if you haven't already.This log was made over GPIB, and the actual length of the data is more than 8 digit. The logging script is "combat tested", this is what I had on hand to run quickly, I'll try to modify it to 10 NPLC.On the other hand I dont think the setting would be unfair. I see two meaning of this tests to find out
Set your NRDGS 1,8
| 0.01 NPLC | 0.1 NPLC | 1 NPLC | 10 NPLC | 50 NPLC | 100 NPLC | 1000 NPLC | |
| 200mV | +11 | +10 | +7 | +3 | +4 | +5 | +9 |
| 2V | +11 | +10 | +7 | +2 | +4 | +5 | +9 |
| 20V | +11 | +10 | +1 | Primary | +4 | +5 | +5 |
| 200V | +11 | +10 | +8 | +6 | +8 | +9 | +9 |
| 1000V | +11 | +10 | +8 | +6 | +8 | +9 | +9 |
Hi everybody,
I own a 34461A since more than 1 month now. This is my first decent bench DMM. Hope than I will not become a volt nut !!! :palm:
Hi everybody,
I own a 34461A since more than 1 month now. This is my first decent bench DMM. Hope than I will not become a volt nut !!! :palm:
Hi Jean,
Why not becoming a volt-nuts?
It's fun.. And.. Sorry, you already lost the game.. You are already a volt-nuts, as you bought that DMM, I think.
Btw.: It's Koningsdag, soon.. I' m curious how the Dutch will celebrate that!
Frank
If I am right, other DMMs like the 34401A do not have any forced colling system.Correct, no fan and no holes on case for cooling
...I completely disagree. Oversampling (averaging multiple samples) is a legitimate way of reducing noise and increasing the effective resolution of an ADC, within the limitations of its linearity.
Averaging by math (either by meter functions or computer-aided) should be avoided, as it's just a pandora box of post-processing and not exactly what this study here for. One can take 0.01 NPLC set of data, and give a median from it with zero noise, but that would not show anything about noise pk-pk.
It is unlikely for anyone to go to the math menu start averaging for taking a single measurement.It is not necessary to do that. Set the filter to N samples, Repeat mode (not windowed or moving average). Then you get one reading per N samples. Filter can be enabled or disabled with a single button press.
I suspected there was a relation between this drifts and the forced cooling system used on this DMM, and decided to log data with the DMM in normal "configuration", and also with the series of holes placed on both sides blocked whith a piece of paper and adhesive tape (but fan still running).
The results are shown on the graph below and pretty obvious.
Furthermore, I noticed that the temperature reported by the DMM is less (yes LESS), when the air entrance are blocked (-1.5 to -2 degrees Celsius)!!!
I repeated this test 3 times and there is absolutly no doubt about the results.
So, I am really wondering about this cooling design and it's effects.
If I am right, other DMMs like the 34401A do not have any forced colling system.
The 34460A do not have any fan. Is anybody there could do some data logging?
Same with the 34461A. I am curious to see the results of other users doing the same (with and without blocking the air entrance).
Thanks for your feedback.I suspected there was a relation between this drifts and the forced cooling system used on this DMM, and decided to log data with the DMM in normal "configuration", and also with the series of holes placed on both sides blocked whith a piece of paper and adhesive tape (but fan still running).
The results are shown on the graph below and pretty obvious.
Furthermore, I noticed that the temperature reported by the DMM is less (yes LESS), when the air entrance are blocked (-1.5 to -2 degrees Celsius)!!!
I repeated this test 3 times and there is absolutly no doubt about the results.
So, I am really wondering about this cooling design and it's effects.
If I am right, other DMMs like the 34401A do not have any forced colling system.
The 34460A do not have any fan. Is anybody there could do some data logging?
Same with the 34461A. I am curious to see the results of other users doing the same (with and without blocking the air entrance).
How stable is the temperature of the environment you are in?
I have been told (by someone at Keysight) that the lesser specifications of the 34460A is due to the lack of a fan, with the readings changing depending on whether the tilting bail is covering the side holes. They also said that the fan, in the 34461/65/70A, moves very little air at room temperature and is largely there for use in equipment racks (although this isn't a recommendation to unplug it).
The 34401A does not have a fan, but some of the Keithley's do (e.g. 2001). So a fan is not necessarily a bad thing, but it requires that the airflow is properly designed.
I am intending to perform these noise measurements on my 34461A and 2000, but I currently don't have a good way of shorting the input jacks - has anyone got any cheap recommendations on something I can pick up here in the UK?
In the Solartron 7081 all of the floating point routines located in the earthed MPU ROM. In "normal" mode (with DIG FILT=off) there is no any filtering of the ADC results, but only (a*x+b) calculations with raw data.
Unfortunately, I can't capture 7081 now, but I have some old data.
It does look way too waivy. Please check if there is some AC hum coupled to meter.
It does look way too waivy. Please check if there is some AC hum coupled to meter.
To compare the ADC I assume you will need to divide by the used range, also only compare the same number of PLCs, the distribution graphs would then be in ppm. (not nV)I agree that ppm makes a lot more sense than absolute voltage.
Meaning ppm from range?Yes, ppm of (nominal) full scale of the range being tested. The range being tested (e.g. 2 VDC) should be including in each graph to give proper context.
Representation is easy to modify.
0.01 NPLC 0.1 NPLC 1 NPLC 10 NPLC 50 NPLC 100 NPLC 1000 NPLC
Why would you think that a 0.00000000 is not a valid sample? It is just as valid as any other!
0.01 NPLC 0.1 NPLC 1 NPLC 10 NPLC 50 NPLC 100 NPLC 1000 NPLC
TiN,
I have been busy this past week but I believe I have the 3458A working with all 35 data sets in an automatic acquisition. I hope to modify it with little changes on the newer SCPI meters. I can create all 35 files with one run.
I just need clarification on the data set sizes. I have the script written to acquire based on NPLC size. Would you break down a list of samples / NPLC? Dr Frank mentioned up to 10K samples on the .01NPLC setting and decreasing from there. I just have to plug in the numbers and run the test.
I do have one odd issue that is nagging me. Occasionally, the meter will output a perfect 0.0000000 reading. It is annoying and I don't think it is a good sample. I will add code to ignore it unless you believe there is reason to keep it. I have attached the file. I will try this on another 3458A to see if this may be part of the controller or software.
function parserk(d) {
d.vmeas = +((d.vk15 / 2) * 1e6)-0.395;
d.v2002 = +((d.vk2002 / 2) * 1e6)+1.42;
d.vk13 = +((d.vk13 / 2) * 1e6)+0.74;
d.vk12 = +((d.vk12 / 2) * 1e6)+0.32;
return d;
}
Why I want combine multiple data sets on same graph? Well, this will allow to have multiple ranges and/or multiple NPLC settings shown by one graph on same meter. I don't think comparing 32 graphs for one meter with 32 graphs for another meter would be great idea..
Any suggestions?
Why I want combine multiple data sets on same graph? Well, this will allow to have multiple ranges and/or multiple NPLC settings shown by one graph on same meter. I don't think comparing 32 graphs for one meter with 32 graphs for another meter would be great idea..
Any suggestions?
Sequence[0] := '32'; Sequence[1] := '22'; Sequence[2] := '31'; Sequence[3] := '30'; Sequence[4] := '--'; Sequence[5] := '--'; Sequence[6] := '--';
Sequence[7] := '--'; Sequence[8] := '--'; Sequence[9] := '--'; Sequence[10] := '--'; Sequence[11] := '33'; Sequence[12] := '34'; Sequence[13] := '20';
Sequence[14] := '21'; Sequence[15] := '23'; Sequence[16] := '24'; Sequence[17] := '--'; Sequence[18] := '--'; Sequence[19] := '--'; Sequence[20] := '--';
Sequence[21] := '--'; Sequence[22] := '--'; Sequence[23] := '--'; Sequence[24] := '--'; Sequence[25] := '10'; Sequence[26] := '11'; Sequence[27] := '12';
Sequence[28] := '13'; Sequence[29] := '14'; Sequence[30] := '00'; Sequence[31] := '01'; Sequence[32] := '02'; Sequence[33] := '03'; Sequence[34] := '04';
I have attached a script that works with the Keithley 2001 and EZGPIB. It will acquire all 20 different Range/NPLC combinations and has been tested with both the Prologix USB and Ethernet adapters.I had meant to reply earlier.
The original script I posted was rewritten and and is based on the 3458A script. The output was formatted similar to TiN's sample data.
I will post the 3458A script tomorrow when I finish the first run and verify the results.
Dr. FrankThe script should issue one "READ" to initiate measurements, then go into the big loop doing "DATA?" repeatedly.
Graphing script does not calculate RMS noise, as well as SD, mean, min, max values and sample window math, but that would be not hard to add after we get all display data format and representation finalized.
macboy
I used READ? as well before. And simply changing READ to FETCH or DATA does not work well, with DATA it does not actually trigger measurement, but just takes reading, while FETCH gives bunch of errors when trying to run on two meters, blocking both.
P.S. Also funny note, running EZGPIB makes my one of my 2001's emit high-pitched buzz. I hear electrons moving in meter's brain, as buzz is different when sampling at different NPLCs :) Did not had it before with LabView.
The script should issue one "READ" to initiate measurements, then go into the big loop doing "DATA?" repeatedly.
Hi,I like this chart, it is a very informative way to present the data. It clearly shows the tradeoff between integration time (i.e. sampling speed) and noise or effective resolution. It also illustrates that the 100 mV range on this instrument is practically limited by the ten-fold increase in noise over the 1 V range, and that the 1 V range still has good noise performance. I would be curious to see at what point the noise takes off for other insturments.
I did 12 measurements, NPLC 0.1 / 1 / 10 / 100 for DC 0.1V / 1V / 10V.
The standard deviation for each measurement equals the RMS noise.
The attached diagram clearly summarizes the HP3458A noise specification and the real measurements.
(I will upload the csv files later.)
Frank
import time
#import usbtmc as tmc
#inst=tmc.instrument(tmc.KEYSIGHT_34461A)
import ethernet
inst=ethernet.instrument('192.168.0.19')
def error_check():
while True:
error=inst.ask('syst:err?')
if error[:2]=='+0':
return
print error
print 'ID: {}'.format(inst.ask('*idn?'))
uptime=inst.ask('syst:upt?').split(',')
print 'Uptime: {} {:02}:{:02}:{:02}, line frequency: {} Hz, temperature: {}'.format(
int(uptime[0]), int(uptime[1]), int(uptime[2]), int(uptime[3]),
int(inst.ask('syst:lfr?')), float(inst.ask('syst:temp?')))
print 'Cal string: {}, cal date: {}, cal temperature: {}'.format(
inst.ask('cal:str?'), inst.ask('cal:date?'), float(inst.ask('cal:temp?')))
inst.write('*rst')
inst.write('*cls')
inst.write('abort')
inst.write("sens:func 'volt:dc'")
inst.write('volt:null:stat off')
inst.write('volt:zero:auto on') # auto zero on
inst.write('volt:imp:auto on') # enable high impendance for 0.1, 1 and 10 vdc
inst.write('disp:stat off') # disables the screen
# triggering
inst.write('trig:sour imm')
# as fast as possible
inst.write('trig:del:auto on')
# once per second
#inst.write('trig:del 1')
inst.write('volt:range 10')
error_check()
#dcv ranges - 0.1 1 10 100 1000
#plc - 0.02 0.2 1 10 100 (rdgs/s 1000, 300, 50, 5, 0.5)
nplc= ['0.02', '0.2', '1', '10', '100']
sample_count= ['1000', '300', '50', '5', '1']
trigger_count=['1800', '1800', '1800', '1800', '900']
for i in range(0, 5):
print 'nplc: {}, samples: {}, count: {}'.format(nplc[i], sample_count[i], trigger_count[i])
print 'temperature: {}, time: {}'.format(float(inst.ask('syst:temp?')),
time.strftime('%d%m%y-%H%M%S'))
# measurement set up
inst.write('volt:nplc {}'.format(nplc[i]))
inst.write('samp:count {}'.format(sample_count[i]))
inst.write('trig:count {}'.format(trigger_count[i]))
error_check()
inst.write('init')
num_results=int(sample_count[i])*int(trigger_count[i])
# reading
results=[]
while len(results)<num_results:
resp=inst.ask('r?')
header_length=int(resp[1])
data_length=resp[2:2+header_length]
if int(data_length)==0:
time.sleep(1)
else:
results+=resp[2+len(data_length):].split(',')
print 'temperature: {}, time: {}'.format(float(inst.ask('syst:temp?')),
time.strftime('%d%m%y-%H%M%S'))
with open('34461a-10vdc-{}-{}.dat'.format(nplc[i], time.strftime('%d%m%y-%H%M%S')), 'w') as f:
for result in results:
f.write('{}\n'.format(result))
error_check()
The second temperature and time output (after the reading loop) was added after I had started the first run.The 0.02 range shows some strange behaviour - with some strange oscillations. The data on dropbox, also has a second run on the 0.02 range completed after the first run through, which does exactly the same. So I'm not sure what is going on there.
The 0.02 range shows some strange behaviour - with some strange oscillations. The data on dropbox, also has a second run on the 0.02 range completed after the first run through, which does exactly the same. So I'm not sure what is going on there.
I already observed that behaviour with my 34461A / 50Hz, but this does not occur only at 0.02 PLC. If you look carrefully, you will observe the same at other PLC n°.
The "step" value at 10V, 0.02 PLC is close to 100µV, but not exactly. A bit less ... Hummm ...
I can't yet explain it. Something to do with the sampling / AD mechanism?
I'am close to 60 years old but still an "apprentit" voltnut. May be the "senior" voltnuts here have some ideas ?
I wonder how the resolution really works (not familiar with the ADC of the 34461A). The real 10V range is 11V, so we should see 1.1mV steps but you;re seeing slightly less than 100uV...
Below, some datas at 10 Volts and 0.02 PLC.
The 0.02 range shows some strange behaviour - with some strange oscillations. The data on dropbox, also has a second run on the 0.02 range completed after the first run through, which does exactly the same. So I'm not sure what is going on there.
I already observed that behaviour with my 34461A / 50Hz, but this does not occur only at 0.02 PLC. If you look carrefully, you will observe the same at other PLC n°.
The "step" value at 10V, 0.02 PLC is close to 100µV, but not exactly. A bit less ... Hummm ...
I can't yet explain it. Something to do with the sampling / AD mechanism?
I'am close to 60 years old but still an "apprentit" voltnut. May be the "senior" voltnuts here have some ideas ?
Below, some datas at 10 Volts and 0.02 PLC.
I wonder how the resolution really works (not familiar with the ADC of the 34461A). The real 10V range is 11V, so we should see 1.1mV steps but you;re seeing slightly less than 100uV...
Is the issue the discrete steps? If you believe the resolution tables, e.g.:
http://rfmw.em.keysight.com/bihelpfiles/Truevolt/WebHelp/US/Content/Misc_Definitions/Range-Resolution_Relationships.htm#kanchor581 (http://rfmw.em.keysight.com/bihelpfiles/Truevolt/WebHelp/US/Content/Misc_Definitions/Range-Resolution_Relationships.htm#kanchor581)
The 34461A at 0.02PLC has a resolution factor of 100ppm, which would mean 1mV on the 10V range.
So I am not surpised to see discrete steps, but I am surprised to see them at 100uV...
As far as the jitter still noticeable at 0.02PLC, it could be due to AutoZero being ON? Even at 10V there will be small offsets that will be compensated and create jitter (although the offsets should also be read out with the same 0.02PLC resolution). I wonder if you'll see pure discrete steps if you turn it off.
The 0.02 range shows some strange behaviour - with some strange oscillations. The data on dropbox, also has a second run on the 0.02 range completed after the first run through, which does exactly the same. So I'm not sure what is going on there.
I already observed that behaviour with my 34461A / 50Hz, but this does not occur only at 0.02 PLC. If you look carrefully, you will observe the same at other PLC n°.
The "step" value at 10V, 0.02 PLC is close to 100µV, but not exactly. A bit less ... Hummm ...
I can't yet explain it. Something to do with the sampling / AD mechanism?
I'am close to 60 years old but still an "apprentit" voltnut. May be the "senior" voltnuts here have some ideas ?
Below, some datas at 10 Volts and 0.02 PLC.
I will try it as well as process data we gathered on friday, we have national holiday here , so will finally get some time to do something. :bullshit:
Will also test it on 2002 and 2400 for you.
I don't know how much of my data collection was created with the wrong LF value, and don't know how it really affects the noise measurement.
If anyone here owns a 344xxA model running on 50 Hz power line, please test it, and give me your thoughts about this bug.
My second issue is related to quick temperature drifts affecting the 10 and 100 PLC datas series. Again, it seems that this fan is bringing more trouble than benefit, at least in a normal room temperature condition. (see post #61, page 4). The story is certainly different in a rack configuration in a hot environement where a forced cooling system is necessary.I have ran some tests of my own (I need to upload the data), and whilst covering the sides seems to effect the offset value, it does not affect the noise - the histograms with and without the sides covered look almost identical.
I ran a test with different cooling configurations and will report later ...
I don't know how much of my data collection was created with the wrong LF value, and don't know how it really affects the noise measurement.
If anyone here owns a 344xxA model running on 50 Hz power line, please test it, and give me your thoughts about this bug.
For the data collection, were you performing a front panel reset before hand? And how were you collecting the data - front panel or remote script?My second issue is related to quick temperature drifts affecting the 10 and 100 PLC datas series. Again, it seems that this fan is bringing more trouble than benefit, at least in a normal room temperature condition. (see post #61, page 4). The story is certainly different in a rack configuration in a hot environement where a forced cooling system is necessary.I have ran some tests of my own (I need to upload the data), and whilst covering the sides seems to effect the offset value, it does not affect the noise - the histograms with and without the sides covered look almost identical.
I ran a test with different cooling configurations and will report later ...
How much of a temperature drift are you talking about? I've noticed that if the ambient temperature changes by 1 to 2 degrees (C) the histogram will be double peaked.
It is very easy to blame the fan, but with regards to noise and warm up time, I haven't seen any difference with the sides covered or not. I did notice similar behaviour to the graph in your post (#51), but this seems to just be a change in the offset value.
Fan:
I suspect that the fan is creating some turbulences into the DMM resulting into non homogeneous temperature over sensitive components.
I am surprised that you don't see any difference with the sides covered or not. I ran yesterday another test from front panel, with the correct LF setting and manual recording of the DMM internal temperature. To cover the sides, I used some rectangular pieces of magnetic ribbon.
Everything is summarized in the graph below.
The results are, for me, obvious, and best results are achieved with sides covered and fan off ...
| non-covered | covered | |
| min | -9.024061e-07 | -6.228938e-06 |
| max | 7.918318e-07 | -4.592069e-06 |
| range | 1.694238e-06 | -5.314253e-06 |
| mean | -1.44677e-08 | 1.636869e-06 |
@OldNeuronsYes ...!
I also just noticed that you are using the 100 mV range - have you been consistently using 100 mV for these readings?
All of the readings I have been doing are on the 10 V range (as it will have the best accuracy for measuring the noise of the ADC).I have no problem with 10 V range as I already mentionned.
@OldNeuronsYes ...!
I also just noticed that you are using the 100 mV range - have you been consistently using 100 mV for these readings?All of the readings I have been doing are on the 10 V range (as it will have the best accuracy for measuring the noise of the ADC).I have no problem with 10 V range as I already mentionned.
Something that I meant to ask before - are you shorting the front or rear terminals?
Additionally, when you use the front panel to make measurements, do you start the measurements then leave it alone? I have noticed, when doing other measurements (resistance), that moving near the input jacks can affect the readings.
Where the hell did you mention that? It seems I've been comparing apples and oranges :palm:
Right then, I will try doing some measurements on the 100 mV, and probably 1 V, ranges.
Where the hell did you mention that? It seems I've been comparing apples and oranges :palm:
Right then, I will try doing some measurements on the 100 mV, and probably 1 V, ranges.
DMM main settings are indicated on the X axis graph.
these measurements, and especially the overview diagram are well done!
I think we'll open une bouteille de Moussy Maurice, ce soir.. :popcorn:
One question: the NPLC 0.02 and NPLC 0.2, are these measurements done in real time, i.e. each 40µs / 400µs?
Are there going to be a explained summary about the less noise ones in different price ranges and such? That would be amazing!
What do you mean? Sorry, maybe my English skills need improvements.Are there going to be a explained summary about the less noise ones in different price ranges and such? That would be amazing!
that kind of summary would be hell with the used markets.
Since these are mostly models of DMMs which are no longer produced, all purchases would be used items. Prices vary so widely on the used market, it would be very difficult to provide the breakdown you requested.What do you mean? Sorry, maybe my English skills need improvements.Are there going to be a explained summary about the less noise ones in different price ranges and such? That would be amazing!
that kind of summary would be hell with the used markets.
What do you mean? Sorry, maybe my English skills need improvements.Are there going to be a explained summary about the less noise ones in different price ranges and such? That would be amazing!
that kind of summary would be hell with the used markets.
Those can be marked as special cases, right?What do you mean? Sorry, maybe my English skills need improvements.Are there going to be a explained summary about the less noise ones in different price ranges and such? That would be amazing!
that kind of summary would be hell with the used markets.
the fluctuating prices. like the keithley 2000 and 2001, you probably wouldn't buy new with the great used market and age of the design. the 2002 is sort of uninteresting in comparison to the agilent 3458 or the fluke 8508. the agilent 34401 hasn't been discontinued, but it's not a great buy with the 34461/65/70, etc.
I uploaded several scripts to the xDevs ftp server. They are for the Keithley 2400, HP 34420A, and Fluke 8846A (finally). The 8846A was challenging and several of the changes were added to all the scripts to deal with the random timeouts from the 8846A. The 2001 and 2002 scripts were also modified and replaced. The 34420A is configurable to either input channel.
I am finally getting around to collecting data. I just uploaded a dataset for one 8846A. I will be adding more through the week.
I was using a different login/pwd. I followed the link in the first post and created a directory called EZGPIB_Scripts.They are visible now. Thank you.
They should be downloadable now.
ManateeMafia,
I did some runs on 2001, but had some issues (unrelated to script) and still need little more time.
Hope to post summary and details this weekend.
import csv
import sys
import math
import glob
from math import exp, expm1
from datetime import datetime
#with open('Keithley2002_DCVOLT1000_NPLC1.csv','r') as i:
with open('output.txt','wb') as o:
for filename in glob.glob('*.csv'):
i = open(filename, 'r')
reader = csv.DictReader(i)
#o.write ("date,Keithley2002\r\n")
sum = 0
sqsum = 0
cnt = 0
for row in reader:
#d = datetime.strptime(row['date'], '%d-%m-%Y %H:%M:%S')
#date = d.strftime('%Y-%m-%d %H:%M:%S')
sum = sum + float(row['Keithley2002'])
sqsum = sqsum + pow(float(row['Keithley2002']),2)
cnt = cnt + 1
avg = sum / cnt
rms = math.sqrt(sqsum / cnt)
#print ("Counts %d, RAW:%s SUM:%.8f AVG: %.8f" % (cnt,row['Keithley2002'],sum,avg))
print ("%s ; Counts %d ; RAW:%s ; SQSUM:%.12f ; AVG: %E ; RMS: %E ;" % (filename,cnt,row['Keithley2002'],sqsum,avg,rms))
i.close()
o.write ("%s ; Counts %d ; RAW:%s ; SQSUM:%.12f ; AVG: %E ; RMS: %E ;\n" % (filename,cnt,row['Keithley2002'],sqsum,avg,rms))
Keithley2002_DCVOLT.1_NPLC.01.csv ; Counts 25173 ; RAW:+0.001932E-03 ; SQSUM:0.000000108820 ; AVG: 1.866774E-06 ; RMS: 2.079154E-06 ;
Keithley2002_DCVOLT.1_NPLC.1.csv ; Counts 3087 ; RAW:+0.006889E-03 ; SQSUM:0.000000172460 ; AVG: 7.467759E-06 ; RMS: 7.474385E-06 ;
Keithley2002_DCVOLT.1_NPLC1.csv ; Counts 29111 ; RAW:+0.002913E-03 ; SQSUM:0.000000296672 ; AVG: 3.187090E-06 ; RMS: 3.192345E-06 ;
Keithley2002_DCVOLT.1_NPLC10.csv ; Counts 3171 ; RAW:+0.003173E-03 ; SQSUM:0.000000030584 ; AVG: 3.101818E-06 ; RMS: 3.105641E-06 ;
Keithley2002_DCVOLT1000_NPLC.01.csv ; Counts 36037 ; RAW:+0.00042E+00 ; SQSUM:0.423976726800 ; AVG: 7.061392E-04 ; RMS: 3.430020E-03 ;
Keithley2002_DCVOLT1000_NPLC.1.csv ; Counts 27187 ; RAW:-0.00007E+00 ; SQSUM:0.004349389700 ; AVG: 2.049807E-04 ; RMS: 3.999756E-04 ;
Keithley2002_DCVOLT1000_NPLC1.csv ; Counts 3085 ; RAW:+0.00017E+00 ; SQSUM:0.000122373500 ; AVG: 1.851572E-04 ; RMS: 1.991664E-04 ;
Keithley2002_DCVOLT1000_NPLC10.csv ; Counts 3146 ; RAW:+0.00018E+00 ; SQSUM:0.000123968200 ; AVG: 1.930960E-04 ; RMS: 1.985070E-04 ;
Keithley2002_DCVOLT100_NPLC.01.csv ; Counts 37259 ; RAW:+0.008344E+00 ; SQSUM:1.047291303500 ; AVG: -1.429550E-04 ; RMS: 5.301737E-03 ;
Keithley2002_DCVOLT100_NPLC.1.csv ; Counts 27343 ; RAW:+0.000114E+00 ; SQSUM:0.000865851267 ; AVG: 1.351317E-04 ; RMS: 1.779502E-04 ;
Keithley2002_DCVOLT100_NPLC1.csv ; Counts 24049 ; RAW:+0.000233E+00 ; SQSUM:0.001122555603 ; AVG: 2.130842E-04 ; RMS: 2.160506E-04 ;
Keithley2002_DCVOLT100_NPLC10.csv ; Counts 3155 ; RAW:+0.000228E+00 ; SQSUM:0.000136496793 ; AVG: 2.070285E-04 ; RMS: 2.079991E-04 ;
Keithley2002_DCVOLT10_NPLC.01.csv ; Counts 37220 ; RAW:+0.0000020E+00 ; SQSUM:0.005388871941 ; AVG: 1.830596E-04 ; RMS: 3.805053E-04 ;
Keithley2002_DCVOLT10_NPLC.1.csv ; Counts 6671 ; RAW:+0.0000119E+00 ; SQSUM:0.000001456198 ; AVG: 1.244638E-05 ; RMS: 1.477457E-05 ;
Keithley2002_DCVOLT10_NPLC1.csv ; Counts 32311 ; RAW:+0.0000139E+00 ; SQSUM:0.000003083435 ; AVG: 9.409851E-06 ; RMS: 9.768822E-06 ;
Keithley2002_DCVOLT10_NPLC10.csv ; Counts 3080 ; RAW:+0.0000012E+00 ; SQSUM:0.000000008606 ; AVG: 1.401396E-06 ; RMS: 1.671587E-06 ;
Keithley2002_DCVOLT1_NPLC.01.csv ; Counts 29560 ; RAW:+0.00000191E+00 ; SQSUM:0.000022246224 ; AVG: 5.251152E-06 ; RMS: 2.743317E-05 ;
Keithley2002_DCVOLT1_NPLC.1.csv ; Counts 3086 ; RAW:+0.00000786E+00 ; SQSUM:0.000000169236 ; AVG: 7.365016E-06 ; RMS: 7.405402E-06 ;
Keithley2002_DCVOLT1_NPLC1.csv ; Counts 6726 ; RAW:+0.00000300E+00 ; SQSUM:0.000000052482 ; AVG: 2.784019E-06 ; RMS: 2.793349E-06 ;
Keithley2002_DCVOLT1_NPLC10.csv ; Counts 3080 ; RAW:+0.00000317E+00 ; SQSUM:0.000000026442 ; AVG: 2.924023E-06 ; RMS: 2.930037E-06 ; Keithley2002_DCVOLT.2_NPLC.01.csv ; Counts 28500 ; RAW:+0.012987E-03 ; SQSUM:0.000001055413 ; AVG: 3.677938E-06 ; RMS: 6.085394E-06 ;
Keithley2002_DCVOLT.2_NPLC.1.csv ; Counts 28500 ; RAW:-0.000484E-03 ; SQSUM:0.000000002879 ; AVG: 8.280295E-08 ; RMS: 3.178376E-07 ;
Keithley2002_DCVOLT.2_NPLC1.csv ; Counts 28500 ; RAW:+0.001461E-03 ; SQSUM:0.000000050083 ; AVG: 1.319546E-06 ; RMS: 1.325635E-06 ;
Keithley2002_DCVOLT.2_NPLC10.csv ; Counts 1190 ; RAW:+0.001523E-03 ; SQSUM:0.000000001753 ; AVG: 1.209540E-06 ; RMS: 1.213718E-06 ;
Keithley2002_DCVOLT1000_NPLC.01.csv ; Counts 28750 ; RAW:+0.00110E+00 ; SQSUM:0.060372603700 ; AVG: 1.076401E-03 ; RMS: 1.449109E-03 ;
Keithley2002_DCVOLT1000_NPLC.1.csv ; Counts 28500 ; RAW:-0.00038E+00 ; SQSUM:0.004084380200 ; AVG: 1.501102E-04 ; RMS: 3.785652E-04 ;
Keithley2002_DCVOLT1000_NPLC1.csv ; Counts 28500 ; RAW:+0.00016E+00 ; SQSUM:0.000835754000 ; AVG: 1.568912E-04 ; RMS: 1.712446E-04 ;
Keithley2002_DCVOLT1000_NPLC10.csv ; Counts 1190 ; RAW:+0.00020E+00 ; SQSUM:0.000025156800 ; AVG: 1.392437E-04 ; RMS: 1.453966E-04 ;
Keithley2002_DCVOLT200_NPLC.01.csv ; Counts 28500 ; RAW:+0.001165E+00 ; SQSUM:0.522674665140 ; AVG: 3.491382E-05 ; RMS: 4.282460E-03 ;
Keithley2002_DCVOLT200_NPLC.1.csv ; Counts 28500 ; RAW:+0.000166E+00 ; SQSUM:0.000580846443 ; AVG: 3.007274E-05 ; RMS: 1.427606E-04 ;
Keithley2002_DCVOLT200_NPLC1.csv ; Counts 28500 ; RAW:+0.000166E+00 ; SQSUM:0.000487367848 ; AVG: 1.260648E-04 ; RMS: 1.307694E-04 ;
Keithley2002_DCVOLT200_NPLC10.csv ; Counts 1190 ; RAW:+0.000117E+00 ; SQSUM:0.000014781988 ; AVG: 1.099160E-04 ; RMS: 1.114533E-04 ;
Keithley2002_DCVOLT20_NPLC.01.csv ; Counts 28250 ; RAW:+0.0000094E+00 ; SQSUM:0.000002496170 ; AVG: 9.400000E-06 ; RMS: 9.400000E-06 ;
Keithley2002_DCVOLT20_NPLC.1.csv ; Counts 28250 ; RAW:+0.0000094E+00 ; SQSUM:0.000001865081 ; AVG: 5.507855E-06 ; RMS: 8.125305E-06 ;
Keithley2002_DCVOLT20_NPLC1.csv ; Counts 28250 ; RAW:+0.0000014E+00 ; SQSUM:0.000000234585 ; AVG: 2.560676E-06 ; RMS: 2.881647E-06 ;
Keithley2002_DCVOLT20_NPLC10.csv ; Counts 1190 ; RAW:+0.0000021E+00 ; SQSUM:0.000000005694 ; AVG: 2.013445E-06 ; RMS: 2.187497E-06 ;
Keithley2002_DCVOLT2_NPLC.01.csv ; Counts 28000 ; RAW:+0.00000480E+00 ; SQSUM:0.000080723282 ; AVG: 8.961264E-07 ; RMS: 5.369334E-05 ;
Keithley2002_DCVOLT2_NPLC.1.csv ; Counts 28000 ; RAW:-0.00000018E+00 ; SQSUM:0.000000021068 ; AVG: 1.519464E-07 ; RMS: 8.674316E-07 ;
Keithley2002_DCVOLT2_NPLC1.csv ; Counts 28250 ; RAW:+0.00000111E+00 ; SQSUM:0.000000040999 ; AVG: 1.182998E-06 ; RMS: 1.204699E-06 ;
Keithley2002_DCVOLT2_NPLC10.csv ; Counts 1190 ; RAW:+0.00000106E+00 ; SQSUM:0.000000001203 ; AVG: 9.911765E-07 ; RMS: 1.005444E-06 ;
HP3458A__ID111_DCV.1_NPLC.01.csv ; Counts 43366 ; RAW:1.934592131E-06 ; SQSUM:0.000000075188 ; AVG: -1.572004E-07 ; RMS: 1.316741E-06 ;
HP3458A__ID111_DCV.1_NPLC.1.csv ; Counts 37203 ; RAW:5.277066847E-07 ; SQSUM:0.000000007471 ; AVG: 1.015909E-07 ; RMS: 4.481187E-07 ;
HP3458A__ID111_DCV.1_NPLC1.csv ; Counts 26937 ; RAW:-1.160974125E-07 ; SQSUM:0.000000001669 ; AVG: -1.766057E-07 ; RMS: 2.489070E-07 ;
HP3458A__ID111_DCV.1_NPLC10.csv ; Counts 4909 ; RAW:1.409000080E-07 ; SQSUM:0.000000000104 ; AVG: -1.177160E-07 ; RMS: 1.453049E-07 ;
HP3458A__ID111_DCV.1_NPLC100.csv ; Counts 444 ; RAW:-9.322971815E-08 ; SQSUM:0.000000000006 ; AVG: -1.081460E-07 ; RMS: 1.118537E-07 ;
HP3458A__ID111_DCV.1_NPLC1000.csv ; Counts 54 ; RAW:-1.465289721E-07 ; SQSUM:0.000000000004 ; AVG: -2.635645E-07 ; RMS: 2.857508E-07 ;
HP3458A__ID111_DCV.1_NPLC50.csv ; Counts 1050 ; RAW:-1.359746644E-07 ; SQSUM:0.000000000017 ; AVG: -1.218833E-07 ; RMS: 1.284038E-07 ;
HP3458A__ID111_DCV1000_NPLC.01.csv ; Counts 35418 ; RAW:-1.760964367E-03 ; SQSUM:0.247285785299 ; AVG: 1.443854E-04 ; RMS: 2.642333E-03 ;
HP3458A__ID111_DCV1000_NPLC.1.csv ; Counts 31322 ; RAW:1.761266916E-04 ; SQSUM:0.003887161804 ; AVG: 1.327557E-04 ; RMS: 3.522829E-04 ;
HP3458A__ID111_DCV1000_NPLC1.csv ; Counts 21212 ; RAW:1.585166738E-04 ; SQSUM:0.000154840219 ; AVG: 4.540910E-05 ; RMS: 8.543800E-05 ;
HP3458A__ID111_DCV1000_NPLC10.csv ; Counts 4696 ; RAW:-1.109616452E-04 ; SQSUM:0.000026941396 ; AVG: -6.692175E-05 ; RMS: 7.574361E-05 ;
HP3458A__ID111_DCV1000_NPLC100.csv ; Counts 517 ; RAW:-7.045183825E-05 ; SQSUM:0.000001151042 ; AVG: -4.487046E-05 ; RMS: 4.718461E-05 ;
HP3458A__ID111_DCV1000_NPLC1000.csv ; Counts 53 ; RAW:-4.579369486E-05 ; SQSUM:0.000000095233 ; AVG: -4.064273E-05 ; RMS: 4.238933E-05 ;
HP3458A__ID111_DCV1000_NPLC50.csv ; Counts 1019 ; RAW:-7.221313421E-05 ; SQSUM:0.000002797342 ; AVG: -4.867849E-05 ; RMS: 5.239450E-05 ;
HP3458A__ID111_DCV100_NPLC.01.csv ; Counts 31954 ; RAW:-1.759903619E-04 ; SQSUM:0.012203052480 ; AVG: 2.890893E-04 ; RMS: 6.179760E-04 ;
HP3458A__ID111_DCV100_NPLC.1.csv ; Counts 31054 ; RAW:1.408164788E-04 ; SQSUM:0.003746873958 ; AVG: 3.253337E-04 ; RMS: 3.473568E-04 ;
HP3458A__ID111_DCV100_NPLC1.csv ; Counts 21556 ; RAW:3.696494398E-05 ; SQSUM:0.000056098800 ; AVG: 3.553526E-05 ; RMS: 5.101439E-05 ;
HP3458A__ID111_DCV100_NPLC10.csv ; Counts 4696 ; RAW:-8.625151540E-06 ; SQSUM:0.000001555449 ; AVG: -1.120778E-05 ; RMS: 1.819969E-05 ;
HP3458A__ID111_DCV100_NPLC100.csv ; Counts 517 ; RAW:6.512869530E-06 ; SQSUM:0.000000010226 ; AVG: 1.896423E-07 ; RMS: 4.447513E-06 ;
HP3458A__ID111_DCV100_NPLC1000.csv ; Counts 53 ; RAW:5.280705025E-07 ; SQSUM:0.000000000970 ; AVG: 3.742990E-06 ; RMS: 4.277578E-06 ;
HP3458A__ID111_DCV100_NPLC50.csv ; Counts 1019 ; RAW:-1.179357455E-05 ; SQSUM:0.000000048509 ; AVG: -2.418380E-06 ; RMS: 6.899579E-06 ;
HP3458A__ID111_DCV10_NPLC.01.csv ; Counts 44629 ; RAW:5.282965900E-05 ; SQSUM:0.000033473378 ; AVG: 2.829167E-07 ; RMS: 2.738679E-05 ;
HP3458A__ID111_DCV10_NPLC.1.csv ; Counts 40296 ; RAW:-3.522582372E-06 ; SQSUM:0.000001245022 ; AVG: -4.628066E-06 ; RMS: 5.558499E-06 ;
HP3458A__ID111_DCV10_NPLC1.csv ; Counts 21586 ; RAW:1.409056517E-06 ; SQSUM:0.000000034038 ; AVG: 1.080365E-06 ; RMS: 1.255721E-06 ;
HP3458A__ID111_DCV10_NPLC10.csv ; Counts 4910 ; RAW:-2.113584272E-07 ; SQSUM:0.000000000902 ; AVG: 1.639140E-07 ; RMS: 4.285837E-07 ;
HP3458A__ID111_DCV10_NPLC100.csv ; Counts 367 ; RAW:-5.283960681E-08 ; SQSUM:0.000000000004 ; AVG: -1.665335E-08 ; RMS: 1.080092E-07 ;
HP3458A__ID111_DCV10_NPLC1000.csv ; Counts 54 ; RAW:-5.283960681E-08 ; SQSUM:0.000000000000 ; AVG: -5.707982E-08 ; RMS: 7.202534E-08 ;
HP3458A__ID111_DCV10_NPLC50.csv ; Counts 1059 ; RAW:1.409056182E-07 ; SQSUM:0.000000000033 ; AVG: -1.184525E-07 ; RMS: 1.768822E-07 ;
HP3458A__ID111_DCV1_NPLC.01.csv ; Counts 39630 ; RAW:-3.519855741E-06 ; SQSUM:0.000000382711 ; AVG: 2.404746E-07 ; RMS: 3.107589E-06 ;
HP3458A__ID111_DCV1_NPLC.1.csv ; Counts 26059 ; RAW:3.520460482E-07 ; SQSUM:0.000000007892 ; AVG: 5.182273E-08 ; RMS: 5.503157E-07 ;
HP3458A__ID111_DCV1_NPLC1.csv ; Counts 26998 ; RAW:2.640389526E-07 ; SQSUM:0.000000000876 ; AVG: 6.759768E-08 ; RMS: 1.801146E-07 ;
HP3458A__ID111_DCV1_NPLC10.csv ; Counts 4909 ; RAW:-2.763607045E-07 ; SQSUM:0.000000000155 ; AVG: -1.511198E-07 ; RMS: 1.779424E-07 ;
HP3458A__ID111_DCV1_NPLC100.csv ; Counts 365 ; RAW:-5.984881499E-08 ; SQSUM:0.000000000005 ; AVG: -1.088564E-07 ; RMS: 1.139828E-07 ;
HP3458A__ID111_DCV1_NPLC1000.csv ; Counts 54 ; RAW:-4.224622234E-08 ; SQSUM:0.000000000000 ; AVG: -7.455024E-08 ; RMS: 7.752065E-08 ;
HP3458A__ID111_DCV1_NPLC50.csv ; Counts 1059 ; RAW:2.640388897E-08 ; SQSUM:0.000000000010 ; AVG: -8.820412E-08 ; RMS: 9.886552E-08 ;
I have no doubt that my tests were made in less than perfect conditions.
I think Dr. Frank has a more suitable environment compared to my home. I did cover the connections to reduce air flow across the inputs. I should add the ability to track the internal temp of the 3458A and perform an ACAL DC as needed. I performed the tests in a spare room but I had no way to monitor external influences.
Running the acquisition at night time is the best time for me as I am not playing with the thermostat and interfering in other measureble ways.
I could disconnect wi-fi and my phone repeater. All CFL's will have to be disconnected too.
Okay, I did some testing here regarding one particular issue:
As lot of homelab user instruments are usually not commonly calibrated, there is issue of having possible DC offsets during measurement of input short. These offsets translate to noise RMS offset as well. Meaning that measurement is not noise itself but noise+offset.
I have no doubt that my tests were made in less than perfect conditions.
I think Dr. Frank has a more suitable environment compared to my home. I did cover the connections to reduce air flow across the inputs. I should add the ability to track the internal temp of the 3458A and perform an ACAL DC as needed. I performed the tests in a spare room but I had no way to monitor external influences.
Running the acquisition at night time is the best time for me as I am not playing with the thermostat and interfering in other measureble ways.
I could disconnect wi-fi and my phone repeater. All CFL's will have to be disconnected too.
Could someone make script for EZGPIB to automate data gathering for 34401a via RS232?
I have user guide if some needs it for what are the commands
The error is due to string conversion float to integer ( NPLC <1 is only affected).Hmm... I could swear when I spotted it it was on NPLC 5 and 200V range. Also the error was only displayed on the meters VFD, not the app. It was consistently coming up on some NPLC's and not others.
c:\MyMeasurements\Keithley2015>parse_noise_sd.py
| Multimeter | Range | NPLC | Counts | Sq.sum | Average | SD
| SD,uV |
| Keithley2015 | .2 | .01 | 5751 | 0.07879803 | 1.370162E-05 | 7.952572E-05 | 79.526 |
| Keithley2015 | .2 | .1 | 5771 | -0.02028955 | -3.515777E-06 | 7.034879E-05 | 70.349 |
| Keithley2015 | .2 | 1 | 5771 | -0.01809268 | -3.135102E-06 | 5.318539E-07 | 0.532 |
| Keithley2015 | .2 | 10 | 1977 | -0.00604425 | -3.057284E-06 | 2.250274E-07 | 0.225 |
| Keithley2015 | .2 | 2 | 5691 | -0.01771140 | -3.112177E-06 | 3.840305E-07 | 0.384 |
| Keithley2015 | .2 | 3 | 5651 | -0.01761382 | -3.116938E-06 | 3.198932E-07 | 0.320 |
Traceback (most recent call last):
File "C:\MyMeasurements\Keithley2015\parse_noise_sd.py", line 28, in <module>
sum += float(row[setname[0]])
ValueError: could not convert string to float:
c:\MyMeasurements\Keithley2015>
| Multimeter | Range | NPLC | Counts | Sq.sum | Average | SD | SD,uV |
| Keithley2015 | .2 | .01 | 5751 | 0.07879803 | 1.370162E-05 | 7.952572E-05 | 79.526 |
| Keithley2015 | .2 | .1 | 5771 | -0.02028955 | -3.515777E-06 | 7.034879E-05 | 70.349 |
| Keithley2015 | .2 | 1 | 5771 | -0.01809268 | -3.135102E-06 | 5.318539E-07 | 0.532 |
| Keithley2015 | .2 | 10 | 1977 | -0.00604425 | -3.057284E-06 | 2.250274E-07 | 0.225 |
| Keithley2015 | .2 | 2 | 5691 | -0.01771140 | -3.112177E-06 | 3.840305E-07 | 0.384 |
| Keithley2015 | .2 | 3 | 5651 | -0.01761382 | -3.116938E-06 | 3.198932E-07 | 0.320 |
| Keithley2015 | 1000 | .01 | 5771 | 94.36460087 | 1.635152E-02 | 8.457514E-03 |8457.514 |
| Keithley2015 | 1000 | .1 | 5761 | 0.92711376 | 1.609293E-04 | 3.231371E-03 |3231.371 |
| Keithley2015 | 1000 | 1 | 5791 | -1.60507862 | -2.771678E-04 | 1.998223E-04 | 199.822 |
| Keithley2015 | 1000 | 10 | 1979 | -0.56855857 | -2.872959E-04 | 1.093811E-04 | 109.381 |
| Keithley2015 | 1000 | 2 | 5781 | -1.44770361 | -2.504244E-04 | 1.380668E-04 | 138.067 |
| Keithley2015 | 1000 | 3 | 5621 | -1.44242376 | -2.566134E-04 | 1.150069E-04 | 115.007 |
| Keithley2015 | 200 | .01 | 5771 | 77.94191925 | 1.350579E-02 | 8.357463E-03 |8357.463 |
| Keithley2015 | 200 | .1 | 5741 | 1.32347618 | 2.305306E-04 | 3.198915E-03 |3198.915 |
| Keithley2015 | 200 | 1 | 5761 | -1.33002973 | -2.308679E-04 | 2.014754E-04 | 201.475 |
| Keithley2015 | 200 | 10 | 1983 | -0.50748620 | -2.559184E-04 | 1.025495E-04 | 102.549 |
| Keithley2015 | 200 | 2 | 5771 | -1.23013294 | -2.131577E-04 | 1.483873E-04 | 148.387 |
| Keithley2015 | 200 | 3 | 5271 | -1.16701184 | -2.214024E-04 | 1.216449E-04 | 121.645 |
| Keithley2015 | 20 | .01 | 5781 | 9.22793018 | 1.596252E-03 | 2.811790E-03 |2811.790 |
| Keithley2015 | 20 | .1 | 5781 | -0.93055499 | -1.609678E-04 | 2.621365E-03 |2621.365 |
| Keithley2015 | 20 | 1 | 5771 | -1.65190293 | -2.862421E-04 | 6.020111E-05 | 60.201 |
| Keithley2015 | 20 | 10 | 1981 | -0.46382246 | -2.341355E-04 | 2.073555E-05 | 20.736 |
| Keithley2015 | 20 | 2 | 5731 | -1.52624034 | -2.663131E-04 | 4.305638E-05 | 43.056 |
| Keithley2015 | 20 | 3 | 5091 | -1.28699979 | -2.527990E-04 | 3.755184E-05 | 37.552 |
| Keithley2015 | 2 | .01 | 5771 | 0.86413454 | 1.497374E-04 | 1.060543E-04 | 106.054 |
| Keithley2015 | 2 | .1 | 5771 | 0.00289789 | 5.021472E-07 | 8.178690E-05 | 81.787 |
| Keithley2015 | 2 | 1 | 5771 | -0.02076525 | -3.598207E-06 | 1.954389E-06 | 1.954 |
| Keithley2015 | 2 | 10 | 1977 | -0.00668119 | -3.379459E-06 | 9.923083E-07 | 0.992 |
| Keithley2015 | 2 | 2 | 5741 | -0.01858068 | -3.236488E-06 | 1.398587E-06 | 1.399 |
| Keithley2015 | 2 | 3 | 5521 | -0.01898148 | -3.438051E-06 | 1.270776E-06 | 1.271 |
c:\MyMeasurements\Keithley2015>
Measured noise on L4411A,34411A and 34410A. The noisiest are ranges 1V and 1000V, about 3 times less noise is on 10V range and 1000V range.
Noise calculation has been calculated as st. Dev on NPLC 1,2,10 and 100.
Noise on 100mV was quite high 4 ppm/Range, compared to 0.1 at 10V range.
Source data are in attachment, including .xlsx spreadsheet and Labview program (works only with 34411,34410 and L4411.
Instruments like 34465,34461 and 34401 will follow (measurement data and program support as well).
Program was too big to upload, so I used TiN FTP /Plesa/Agilent
| nplc | stddev | min | 1st quartile | median | mean | 3rd quartile | max |
| 0.001 | 2.30602238797611e-04 | -1.14229665000e-03 | -1.51375433000e-04 | 1.69011405000e-05 | 2.09932992126e-05 | 1.55784426000e-04 | 1.21614729000e-03 |
| 0.002 | 1.15148534465426e-04 | -5.42673578000e-04 | -8.19337900000e-05 | 2.20449659000e-06 | 2.05098039046e-06 | 7.16461393000e-05 | 6.01827570000e-04 |
| 0.006 | 4.66714749030745e-05 | -2.44258223000e-04 | -2.63069927000e-05 | 1.46966440000e-06 | 2.16718026217e-06 | 3.51249791000e-05 | 2.27430565000e-04 |
| 0.02 | 1.68439537307131e-05 | -8.31095216000e-05 | -9.74877382000e-06 | 3.42921692000e-06 | 2.01999992659e-06 | 1.26881026000e-05 | 8.53385126000e-05 |
| 0.06 | 6.82210110147248e-06 | -2.88505975000e-05 | -2.93346187000e-06 | 1.23205398000e-06 | 1.28789662138e-06 | 5.96959490000e-06 | 3.24734229000e-05 |
| 0.2 | 3.86900389895176e-06 | -1.38171905000e-05 | -1.81753708000e-06 | 6.84019333000e-07 | 9.25507110739e-07 | 3.55690053000e-06 | 1.72177438000e-05 |
| 1 | 1.27393700250821e-06 | -4.12866614000e-06 | 4.45708276000e-07 | 1.29020817000e-06 | 1.29184723605e-06 | 2.15816639000e-06 | 6.59179082000e-06 |
| 10 | 3.79754719542073e-07 | -1.05562487000e-07 | 9.89941540000e-07 | 1.25971234000e-06 | 1.25422712073e-06 | 1.50602481000e-06 | 2.79388714000e-06 |
| 100 | 1.3879052042004e-07 | 9.35518214000e-07 | 1.17784276750e-06 | 1.26674983500e-06 | 1.26971653494e-06 | 1.36644774000e-06 | 1.67961645000e-06 |
It would be quite interesting to make this measurement on 34470A and compare it to Keithley DMM7510.
Is there any vollunteer with 34470A or DMM7510?
I will take note not to trust the 1000V range at 0.01 NPLC, it looks pretty bad to me :-/O
Actually I think my figures are nonsense - the ranges are all in 2's, so I expect my 100V measurements are in the 1000V range. I used the K2000 EZGPIB script. I had to throw out the NPLC5 stuff.I will take note not to trust the 1000V range at 0.01 NPLC, it looks pretty bad to me :-/O
Not really. The 100V range is worse, actually, if you look at the ppm of range figure (the worst is 100mV, but that is expected ;) ).
Cheers
Alex
I have to admit I just ran the script as is, and it was stated as beta.
i hope this is not too off topic.
i recall forumner Robrenz mentioned in a thead he has his tek4050 log 152hrs with only 1uV pk-pk noise, and that was amazing.
i recall forumner Robrenz mentioned in a thead he has his tek4050 log 152hrs with only 1uV pk-pk noise, and that was amazing.
I have a vague memory of this, was it done without filtering/math?
Either Way, the 4050/8045A is a very underestimated instrument IMO.
Wife bought me a DMM7510 for X-Mas, so those tests coming up once it arrives.
Pardon my French, but I've been waiting for a DMM7510 to be (measured for noise and/or) added to the list for forever. Dave tested it, Shariar (of SignalPathBlog fame) tested it, others tested it and noone but a single random internet engineer has said dick about or measured its noise characteristics.
Nothing but empty promises of "I'll take a look at it and report back." Hopefully you will not become another data point in that trend of promising and not delivering.
Nothing but empty promises of "I'll take a look at it and report back." Hopefully you will not become another data point in that trend of promising and not delivering.
Wife bought me a DMM7510 for X-Mas, so those tests coming up once it arrives.
Fucking finally, already!
Pardon my French, but I've been waiting for a DMM7510 to be (measured for noise and/or) added to the list for forever. Dave tested it, Shariar (of SignalPathBlog fame) tested it, others tested it and noone but a single random internet engineer has said dick about or measured its noise characteristics.
Nothing but empty promises of "I'll take a look at it and report back." Hopefully you will not become another data point in that trend of promising and not delivering.
So Keithley has outdone themselves, DMM7510 will be here tomorrow according to UPS tracking.
Any interested in standardizing on a .csv format? Items like what header info, submitter info, sample rate, instrument setup, etc?
Shamelessly stolen graph from Dr. Frank, I hope you don't mind, many many thanks in advance. =P
..
Small teaser from the Advantest R6581 8.5digit meter, statistics done in instrument. (where the hell is my GPIB-USB cable grr)
I ran the 10V 100NPLC test a few times, ranged from 0.0084 to 0.0092 ppm/range stdev. I was using the Fluke shorting block, and you know what, I was expecting the R6581 to be much worse than the 3458A on 100NPLC but it's not that bad is it? Maybe I don'tneedwant a 3458A after all...
Do you have any idea, on which basis this R6581 does the Auto Cal , in comparison to the 3458A?
I think there is need to revamp my python knowledge to make it more useful though.
Would be nice if you just follow existing format for now.
What you will run to get GPIB data? I can try to make an script for 7510, but haven't read it's docs yet.
| Multimeter | Range | NPLC | Counts | Sq.sum | Average | SD | SD,uV |
| k2010 | 10 | .01 | 120 | 0.00427245 | 3.560375E-05 | 9.487653E-05 | 94.877 |
| k2010 | 10 | .1 | 120 | -0.00019567 | -1.630594E-06 | 1.470821E-05 | 14.708 |
| k2010 | 10 | 10 | 360 | -0.00070481 | -1.957792E-06 | 5.162154E-07 | 0.516 |
| k2010 | 10 | 1 | 120 | -0.00023459 | -1.954949E-06 | 1.273443E-06 | 1.273 |
| Multimeter | Range | NPLC | Counts | Sq.sum | Average | SD | SD,uV |
| k2450 | 2 | 1 | 121 | -0.00503126 | -4.158066E-05 | 3.858809E-06 | 3.859 |
| k2450 | 2 | 10 | 121 | -0.00469228 | -3.877919E-05 | 3.558100E-06 | 3.558 |
| k2450 | 2 | .1 | 121 | -0.00864380 | -7.143638E-05 | 2.372225E-05 | 23.722 |
| k2450 | 2 | .01 | 121 | -0.04565281 | -3.772959E-04 | 5.115046E-05 | 51.150 |
I think it is done more simply than the 3458A, some clues are in the 24hr range error specification. From 10V>1V>0.1V the range error is 0.1>1>10 ppm. I don't know if the difference are from a worse ADC, or different Auto Cal scheme, or both.
If you have any free time with the 3458A, can you check the error from applying 100mVDC to the 10V range and then reading it from the 100mV range? I get a difference of about 2-5ppm of reading even after an Auto Cal.
Lookingforward to your K7510 update Dr.diesel.
| Multimeter | Range | NPLC | Counts | Sq.sum | Average | SD | SD,uV |
| k7510 | .1 | .01 | 1800 | -0.00946209 | -5.256717E-06 | 7.585452E-06 | 7.585 |
| k7510 | .1 | .1 | 1799 | -0.00845946 | -4.702313E-06 | 4.205452E-06 | 4.205 |
| k7510 | .1 | 1 | 1801 | -0.00984773 | -5.467925E-06 | 4.684346E-07 | 0.468 |
| k7510 | .1 | 10 | 1801 | -0.00976237 | -5.420526E-06 | 1.885766E-07 | 0.189 |
| k7510 | 1 | .01 | 1801 | -0.00793555 | -4.406191E-06 | 7.629865E-06 | 7.630 |
| k7510 | 1 | .1 | 1799 | -0.00784621 | -4.361427E-06 | 3.954875E-06 | 3.955 |
| k7510 | 1 | 1 | 1801 | -0.00977324 | -5.426563E-06 | 4.579941E-07 | 0.458 |
| k7510 | 1 | 10 | 1801 | -0.00979378 | -5.437968E-06 | 1.943267E-07 | 0.194 |
| k7510 | 10 | .01 | 1801 | 0.00635690 | 3.529649E-06 | 1.290502E-05 | 12.905 |
| k7510 | 10 | .1 | 1799 | -0.00104714 | -5.820696E-07 | 4.829904E-06 | 4.830 |
| k7510 | 10 | 1 | 1801 | -0.00204352 | -1.134657E-06 | 7.491898E-07 | 0.749 |
| k7510 | 10 | 10 | 1801 | -0.00203306 | -1.128850E-06 | 4.907266E-07 | 0.491 |
| k7510 | 100 | .01 | 1801 | -0.09902185 | -5.498160E-05 | 1.346015E-03 |1346.015 |
| k7510 | 100 | .1 | 1799 | -0.20888873 | -1.161138E-04 | 1.807134E-04 | 180.713 |
| k7510 | 100 | 1 | 1801 | -0.31506582 | -1.749394E-04 | 5.533520E-05 | 55.335 |
| k7510 | 100 | 10 | 1801 | -0.32145543 | -1.784872E-04 | 1.786285E-05 | 17.863 |
| k7510 | 1000 | .01 | 1801 | 1.33690515 | 7.423127E-04 | 1.674120E-03 |1674.120 |
| k7510 | 1000 | .1 | 1799 | -0.16155031 | -8.980006E-05 | 2.495570E-04 | 249.557 |
| k7510 | 1000 | 1 | 1801 | -0.35094636 | -1.948619E-04 | 8.040639E-05 | 80.406 |
| k7510 | 1000 | 10 | 1802 | -0.35127405 | -1.949357E-04 | 5.129073E-05 | 51.291 |
| Multimeter | Range | NPLC | Counts | Sq.sum | Average | SD | SD,uV |
| k7510 | .1 | 10 | 301 | -0.00024168 | -8.029273E-07 | 5.626927E-08 | 0.056 |
| k7510 | .1 | .1 | 301 | -0.00025192 | -8.369386E-07 | 3.502203E-07 | 0.350 |
| k7510 | .1 | 1 | 301 | -0.00022957 | -7.627042E-07 | 6.791389E-08 | 0.068 |
| k7510 | .1 | .01 | 300 | 0.00098528 | 3.284266E-06 | 5.638453E-07 | 0.564 || Multimeter | Range | NPLC | Counts | Sq.sum | Average | SD | SD,uV |
| k7510 | .1 | .01 | 300 | 0.00098528 | 3.284266E-06 | 5.638453E-07 | 0.564 |
| k7510 | .1 | .1 | 301 | -0.00025192 | -8.369386E-07 | 3.502203E-07 | 0.350 |
| k7510 | .1 | 1 | 301 | -0.00022957 | -7.627042E-07 | 6.791389E-08 | 0.068 |
| k7510 | .1 | 10 | 301 | -0.00024168 | -8.029273E-07 | 5.626927E-08 | 0.056 |
| k7510 | 1 | .01 | 301 | 0.00116343 | 3.865231E-06 | 1.363790E-06 | 1.364 |
| k7510 | 1 | .1 | 301 | -0.00021776 | -7.234496E-07 | 5.733036E-07 | 0.573 |
| k7510 | 1 | 1 | 301 | -0.00028301 | -9.402422E-07 | 1.024698E-07 | 0.102 |
| k7510 | 1 | 10 | 301 | -0.00028457 | -9.454107E-07 | 8.580283E-08 | 0.086 |
| k7510 | 10 | .01 | 301 | 0.00220821 | 7.336241E-06 | 1.301336E-05 | 13.013 |
| k7510 | 10 | .1 | 301 | -0.00016204 | -5.383527E-07 | 2.435271E-06 | 2.435 |
| k7510 | 10 | 1 | 301 | -0.00031698 | -1.053088E-06 | 7.528228E-07 | 0.753 |
| k7510 | 10 | 10 | 301 | -0.00034107 | -1.133112E-06 | 5.040502E-07 | 0.504 |
| k7510 | 100 | .01 | 301 | 0.16086693 | 5.344416E-04 | 7.598755E-04 | 759.875 |
| k7510 | 100 | .1 | 301 | 0.09894463 | 3.287197E-04 | 1.358261E-04 | 135.826 |
| k7510 | 100 | 1 | 301 | 0.10250599 | 3.405514E-04 | 3.750361E-05 | 37.504 |
| k7510 | 100 | 10 | 301 | 0.10177610 | 3.381266E-04 | 2.422995E-05 | 24.230 |
| k7510 | 1000 | .01 | 301 | 0.06277022 | 2.085389E-04 | 1.766823E-03 |1766.823 |
| k7510 | 1000 | .1 | 301 | -0.04796741 | -1.593602E-04 | 2.381594E-04 | 238.159 |
| k7510 | 1000 | 10 | 302 | -0.05574608 | -1.845897E-04 | 5.981283E-05 | 59.813 |
| k7510 | 1000 | 1 | 301 | -0.05423848 | -1.801943E-04 | 7.543913E-05 | 75.439 || Multimeter | Range | NPLC | Counts | Sq.sum | Average | SD | SD,uV |
| k7510 | .1 | .01 | 1800 | 0.00649502 | 3.608347E-06 | 5.157321E-07 | 0.516 |
| k7510 | .1 | .1 | 1801 | -0.00123428 | -6.853294E-07 | 2.515242E-07 | 0.252 |
| k7510 | .1 | 1 | 1801 | -0.00110277 | -6.123113E-07 | 5.430182E-08 | 0.054 |
| k7510 | .1 | 10 | 1801 | -0.00110202 | -6.118930E-07 | 3.105326E-08 | 0.031 |
| k7510 | 1 | .01 | 1801 | 0.00784606 | 4.356503E-06 | 1.394442E-06 | 1.394 |
| k7510 | 1 | .1 | 1801 | -0.00105845 | -5.877040E-07 | 3.416894E-07 | 0.342 |
| k7510 | 1 | 1 | 1801 | -0.00112253 | -6.232788E-07 | 8.595656E-08 | 0.086 |
| k7510 | 1 | 10 | 1801 | -0.00101890 | -5.657409E-07 | 7.448410E-08 | 0.074 |
| k7510 | 10 | .01 | 1801 | 0.01771527 | 9.836353E-06 | 1.266939E-05 | 12.669 |
| k7510 | 10 | .1 | 1801 | -0.00054103 | -3.004068E-07 | 2.496712E-06 | 2.497 |
| k7510 | 10 | 1 | 1801 | -0.00143662 | -7.976804E-07 | 7.432814E-07 | 0.743 |
| k7510 | 10 | 10 | 1801 | -0.00134081 | -7.444814E-07 | 5.072808E-07 | 0.507 |
| k7510 | 100 | .01 | 1801 | 0.89856873 | 4.989277E-04 | 7.725466E-04 | 772.547 |
| k7510 | 100 | .1 | 1801 | 0.56770246 | 3.152151E-04 | 1.102306E-04 | 110.231 |
| k7510 | 100 | 1 | 1801 | 0.59237881 | 3.289166E-04 | 3.473867E-05 | 34.739 |
| k7510 | 100 | 10 | 1801 | 0.58874287 | 3.268978E-04 | 1.637639E-05 | 16.376 |
| k7510 | 1000 | .01 | 1799 | 1.35719201 | 7.544147E-04 | 1.723659E-03 |1723.659 |
| k7510 | 1000 | .1 | 1801 | -0.31368228 | -1.741712E-04 | 2.448538E-04 | 244.854 |
| k7510 | 1000 | 1 | 1801 | -0.35386557 | -1.964828E-04 | 7.926890E-05 | 79.269 |
| k7510 | 1000 | 10 | 1802 | -0.34549073 | -1.917263E-04 | 5.191135E-05 | 51.911 |
ah i see. this is my log in xls for your sample view (should open as with no problem?), column 1 is time reference, column 2 is data in nV. but for TiN's web format i think 9 decimals of data /w scientific notation? i think you need to unlock the numbers after the 6th decimals
@rigrunner, i think if you look at manatee mafia's 3458a log in xdev website, you see that the data is 1.2345-Exx. but your data is only zero and one.
3458A with it's averaging on NPLC > 10 still kills them all with ease.
Perhaps you can share your script
P.S. Let's give little guy some credit too
7510 has much value at $3700.It does indeed. As many already stated, and I agree, 3458A being more a metrology tool, rather than general-purpose bench DMM.
what i dont understand is, if we command APER to capture a window of x samples, it does not depend on cycles like NPLC ?
edit** if based on Dr Franks plot, when we set NPLC 1, i am guessing we should also set APER = 0.02, yes ?
if so, what if we set NPLC =1, but we set APER as something else, 0.5? or its going to introduce more noise?
thanks TiN n Frank. that tip on AZERO also confirmed my assumption about its use. although in my case, it seem to add a tad of noise.
i tried experimenting with cycling AZERO (ie:1 AZERO per 100samples), but it seem to add some non-linearity to long term reading as well. so in my conclusion, i think i will just leave it 100% on. i got this cycling idea from reading the web, but i think it is only usable for certain machines
as i am using RS232, 1 sample of 100NPLC takes approx 6.6seconds to log to PC. NPLC1000 will take about 70 seconds :P (3600 samples = 7days/70days ! shiet ! :P)
At NPLC 1000, the 10V range nearly reaches 9 digits.
Frank
btw, how do we gauge usability of a last digit. is it using noise STDEV? say 10v range 12,345,678.9uV, what should STDEV look like so that the 9th is considered a usable reading?
and also what is the diff between RMS noise and STDEV?
Also on 3458A APER does actually allow integration times longer than 10 NPLC, up to 1 second, while higher NPLC are averaged in digital domain. At least that's what in manual.
but how did Dr franks have such low STDEV?
surely it is something repeatable, to produce similar result if conditions could be similar?
I had runs with 50 samples only, result was very close if not same.
Autozero does nothing to flicker reference noise, as reference voltage is inside the compensation loop already.
try a run at 100NPLC with only 100 samples with Auto Zero on as a sanity check.
Wow, this is a very interesting thread. My own results without auto zero below. I have a coupla questions:
@Dr. Frank
1) - presumably it was the upward tip of the graph which tipped you off to the need for auto zero?
2) - if we compare the non-azero vs the a-zeroed results, presumably that gives a measure for the instrument/ref flicker noise? Would you guess this is short term temperature fluctuation or something else?
3) - did you get your noise spec from reading values off the graph in the datasheet or from somewhere else? (I read mine off the graph)
4) - the split between the spec and the non-auto-zeroed results seems to occur earlier for 100mV and 1/100V ranges. Any thoughts?
5) - (also) does it matter that you're not triggering off the PLC? i.e. you can trigger anywhere in the cycle?
6) - (also) does it matter (re APER and NPLC) that the line frequency isn't an integer at any particular moment or is APER time effectively defined on a line frequency basis (I guess I could RTFM for this one)?
Alan
(http://anagram.net/nuts/MeterNoiseFloor/Images/3458A-01704%20noise%20floor.png)
The instrument has a gain drift of about 0.5ppm/K for the 10V range, and 1.2ppm/K for 1V and 100mV.
ACAL does NOT apply here!
Ambient temperature changes of a few tenths of °C therefore can easily cause drifts of many tenths of ppm.
And that's exactly, what you may see in your measurements.
>>> TiN - Autozero does nothing to flicker reference noise, as reference voltage is inside the compensation loop already.
I don't quite get that - is it possible to explain that further?
The variance (or uncertainty) of a set of N measurements is given by stdv/ sqrt(N).
For the 10V range, you may average over about 50 measurements of NPLC 100 to have 1e-9 variance of the result.
4 averaged measurements of NPLC 1000 also give 1e-9.
I doubt that anything below 1e-8 is useful.
At first, the mentioned environmental parameters are worse, and second, the linearity of the A/D is 2e-8 'only'.
Therefore, any higher resolution is useless.
, I'm seeing something that can only be described as "popcorn noise"-- little positive [or negative] "spikes" in the data that far exceed the input bias current-- seemingly random, but at a far lower rate than the more-or-less normal input noise.Is it something similar to my measurement as attached?
This is a x-post from plesa's 34420a repair thread, but it should be interesting here - a first cut at a 34420a noise floor with an OK but not-perfect short...i.e. a Lemo connector with some copper wire - but not soldered in yet with the specified Sn/Ag solder.
Any 'turning up at the 200 nplc points' might be temperature drift (or just statistical variation - RSE is targeted at 10%). My meter is reporting firmware versions: 9.0-5.0-2.0 btw.
Curiously channel 2 has much lower noise. Whether this is my measurement error or a bad channel 1 or real results, I'm not fully sure - so I would be very interested in someone else verifying this result on their own meter. Looking at the schematic, the channels are asymmetrical (e.g. channel 1 can source current) so it is just possible that the channels have a very different spec. The docs are actually a bit brief on the specified noise floor which is a bit disappointing.
Anyway, I hope that's interesting.
I know that there is a difference between channel-1 and channel-2 --- one of them can go up to 100V and the other one only goes up to 10V, but I can't remember which is which. So, one of the channels is hooked up to a HV divider and possibly some different protection network that might explain the difference in noise performance. What does the manual say about this? My 34420A is in my home laboratory and I'm not there right now, but I will try to test this later tonight.Channel 1 is max 120V rated and channel 2 is max 12V rated. On my repaired unit the channel 1 is little bit more noisier than channel 2.
I came across similar "spikes" several times when I measure a 10V or 7V with my 3458A. Strangely, those spikes were all downwards. This not only happened to me, also happened to others thousand miles away. The reason could be interference from the mains or from the air., I'm seeing something that can only be described as "popcorn noise"-- little positive [or negative] "spikes" in the data that far exceed the input bias current-- seemingly random, but at a far lower rate than the more-or-less normal input noise.Is it something similar to my measurement as attached?
This is my femto-amp meter(DIY), the CMOS input with a very large feedback resistor. I cannot find the source of those spikes neither. Once I even suspect it was the cosmic ray or background radiation because I measure the similar background in my Geiger counter.
Yes, very similar, but my "spikes" are much larger. I also thought that it might be cosmic radiation--- huge bundles of mixed particles and rays at incredibly high energy levels--- it would certainly explain the data perfectly. It would be instructive to connect a recorder to the DMM output, and input a highly divided signal from a radiation detector to the DMM--- that way, you would see a "jump" in the signal with each event from the detector, and you would also be able to see if the spikes coincided with the radiation data ["spike" on top of the "jump"]. OR, if you have multiple DMMs, then record the data from them all simultaneously over GPIB, and then plot the data from each so that you can see if the spikes coincide on two or more meters.
If this is cosmic radiation, well then there is little we would be able to do about it other than a sophisticated filter designed to pass the "normal" data while blocking the "spikes". That would be material for a master's degree thesis...
Not cosmic radiation then-- you would see it in both channels. Might be radioactive particles in the packaging, but I thought they solved that decades ago...Well, the current sources, current-voltage converters, and handheld voltmeters(with data recording ) are all battery powered. The current sources and current-voltage converters are all in their own aluminium cases. I put all of them into a large aluminium box with 4 holes but I cover those holes by coins. Thru one of the holes I can see the voltmeters reading. So I believe what ever the noise is, must come from inside. The earth connection was not shown because I moved the box to the floor for photo.
These are very low current levels, so maybe just shifts in the local field getting picked up? [People walking by, truck goes by in street, etc.] At these levels, to be very honest, we should be using shielded and guarded measurements and special cables [like triax, with the middle shield a driven guard, etc.]. Circuits should have careful consideration to shielding and guarding, etc. Most DMMs don't have this [the 3458A does, but few people make use of it].
Also maybe just quantum mechanics getting us [possibly "hot" electrons being randomly generated in silicon lattice imperfections, with some chips better than others]... Don't know... Beyond my knowledge at this point...
Many thanks for the explanation re ref noise and other noise contributors to the acquisition process - I am beginning to understand now. Also an interesting point about fourier analysis. Below a plot comparing azero on and off (I used the same setting on all nplcs) to counteract drift - presumably the difference is mainly down to temperature drift. With a coupla runs I was able to get an internal temp drift less than 0.1C during the nplc 1,000 run. These are at 60 samples per nplc for a relative standard error in the noise readings of 10% (see error bars). TiN - it would be interesting to run the 'azero on' test on your 'evil' meter - maybe your temperature environment is fairly drifty like mine.This is a very good chart :-+
(edit) fixed the error bars on the chart and added the intervening points.
Alan
(http://anagram.net/nuts/MeterNoiseFloor/Images/10V%20azero%20on%20and%20off%20b.png)
These are very low current levels, so maybe just shifts in the local field getting picked up? [People walking by, truck goes by in street, etc.] At these levels, to be very honest, we should be using shielded and guarded measurements and special cables [like triax, with the middle shield a driven guard, etc.]. Circuits should have careful consideration to shielding and guarding, etc. Most DMMs don't have this [the 3458A does, but few people make use of it].
Also maybe just quantum mechanics getting us [possibly "hot" electrons being randomly generated in silicon lattice imperfections, with some chips better than others]... Don't know... Beyond my knowledge at this point...
use some alternate technology
| NPLC | #samples |
| 0.02 | 100000 |
| 0.06 | 30000 |
| 0.2 | 10000 |
| 1 | 2000 |
| 10 | 200 |
| 100 | 50 |
It was more a poke for all (rightfully busy) people with DMM7510's who had no time to run noise test script on the box :horse:
It's EZGPIB. Details here (https://xdevs.com/article/dmm_noise/). :)
Here is maybe enough data to give a comparison. My short plug is a crappy banana short. I will try a piece of hookup wire to see if that improves the results.
DMM7510
Range NPLC FILT STD DEV READINGS
100mV 10 10 24.3nV 60
100mV 10 off 35.9nV 600
100mV 1 off 39.1nV 6000
1V 10 10 32.7nV 60
1V 10 off 65.6nV 600
1V 1 off 77.3nV 6000
10V 10 10 216nV 60
10V 10 off 344nV 600
10V 1 off 665nV 6000
Here is maybe enough data to give a comparison. My short plug is a crappy banana short. I will try a piece of hookup wire to see if that improves the results.
DMM7510
Range NPLC FILT STD DEV READINGS
100mV 10 10 24.3nV 60
100mV 10 off 35.9nV 600
100mV 1 off 39.1nV 6000
1V 10 10 32.7nV 60
1V 10 off 65.6nV 600
1V 1 off 77.3nV 6000
10V 10 10 216nV 60
10V 10 off 344nV 600
10V 1 off 665nV 6000
10V range 1000PLC 19 readings, standard deviation 85 nV. I will let this run all week and see what happens.
10V range 1000PLC 19 readings, standard deviation 85 nV. I will let this run all week and see what happens.
Did you change instruments? 7510 has a max NPLC of 15.
NPLC 10, Digital filter 100. This is similar to the 3458A which has no aperture greater than 1 second ( if I recall the number correctly from reading in this forum). Everything beyond that is digital filtering.
Are you sure about Keithley DMM7510 to have a max NPLC of 1510V range 1000PLC 19 readings, standard deviation 85 nV. I will let this run all week and see what happens.
Did you change instruments? 7510 has a max NPLC of 15.
Do you have the latest firmware installed?Yes, latest FW 1.6.1 is installed
Do you have the latest firmware installed?Yes, latest FW 1.6.1 is installed
Really interesting, that you can set yours to 15.
50HZ vs 60 Hz
I am in the USA where one PLC is 1/60 of a second.
There are four main noise sources in a DMM:
1) the ADC itself: this gives a constant noise contribution relative to the range.
2) The reference noise: this only applies if a voltage other than 0 is measured - so it does not matter for data on shorted input.
It is proportional to the measured voltage.
3) The noise from the input Amplifier. This noise depends on the range / amplification chose. Usually a constant noise voltage and thus increasingly important in the low voltage ranges.
4) Noise from the input protection / divider: High resistance in the input protection (e.g. series resistance) gives noise, that behaves similar to the amplifier noise. A special case is the typical 9.9 M - 100 K divider resistance, that can contribute to noise especially in the 100 V range.
The noise relative to the full scale in the 0.1 V range at 1 PLC is even lower than in the 10 V range, which is a little strange, but might come from the special kind of range switching used. It's also possible to have quite some quantization noise at 1 PLC and thus a noise level that can change with offsets / the exact measured voltage.
If there would be significant amplifier noise, the 0.1 V range should show a much higher noise than the 10 V range. So the noise must be mainly the range independent ADC noise. It's also typical to have very little amplifier noise for the range without extra amplification (e.g. 10 V range).
A second factor that point towards noise from the ADC is that the noise at 1 PLC is much higher than at 20 PLC. White noise from the amplifier would make the noise go down with the square root of the integration time. With a contribution of 1/f noise the noise would go down even slower with longer time. In contrast to this the ADC can have a noise contribution (e.g quantization or determination of residual charge) that goes down inverse proportional with the integration time - this about what is found here for the 34420. So that ADC is much better at 10/20 PLC than at 1 PLC.
| Range | Speed/Average | 34465A ppm | DMM7510 ppm |
| 100 mv | 1PLC | 2.6 | 0.43 |
| 100 mV | 10 PLC | 1.2 | 0.29 |
| 100mV | 100PLC From 1 PLC | 1.1 | 0.21 |
| 100 mV | 100PLC From 10 PLC | 0.97 | 0.2 |
| 1V | 1PLC | 0.32 | 0.081 |
| 1V | 10PLC | 0.14 | 0.055 |
| 1V | 100PLC From 1 PLC | 0.103 | 0.04 |
| 1V | 100PLC From 10 PLC | 0.098 | 0.033 |
| 10V | 1PLC | 0.13 | 0.081 |
| 10V | 10PLC | 0.04 | 0.051 |
| 10V | 100PLC | 0.016 | NA |
| 10V | 100PLC From 1 PLC | 0.014 | 0.043 |
| 10V | 100PLC From 10 PLC | 0.014 | 0.038 |
| 10V | 1000PLC from 1PLC | 0.01 | 0.019 |
| 10V | 1000PLC from 10PLC | 0.0063 | 0.016 |
There is also a number of programming issues I found on the Keithley DMM7510 meter. It gave me a blue screen of death several times (even Chinese instruments don't really do that). When using internal trigger timer, it tends to hang up and stop triggering after a few thousand to tens of thousand of points. When saving to USB, it does not warn if the file already exists. Overall, 34465A is clearly a great deal with 7.5 digit performance. DMM7510 is questionable if its worth 2-3 times higher price, perhaps it can be improved with firmware.
Unfortunately, my DMM7510 is showing a blue screen of death from time to time as well.
There is also a number of programming issues I found on the Keithley DMM7510 meter. It gave me a blue screen of death several times (even Chinese instruments don't really do that). When using internal trigger timer, it tends to hang up and stop triggering after a few thousand to tens of thousand of points. When saving to USB, it does not warn if the file already exists. Overall, 34465A is clearly a great deal with 7.5 digit performance. DMM7510 is questionable if its worth 2-3 times higher price, perhaps it can be improved with firmware.
I think would also be interesting to see 34470A in comparison too, to see if lower noise LTZ1000 ref helps on time/noise perf.
I think this points to a serious firmware problem.
Its a good idea to post on TEK/Keithley forum, do you mean here? https://forum.tek.com/viewforum.php?f=363
No, 20th point involves averaging data in groups of 21 points, taking difference between successive groups, and calculating standard deviation of that.
Results from a K2010, in cal, Keithley 4-term shorting block.
Range 2 on a k2010 is 10v, FYI.
Could you take more data at faster polling rate and maybe also lower voltage ranges?
Could you take more data at faster polling rate and maybe also lower voltage ranges?
You bet! I got a full house today, but will run the full gambit in the next day or two.
You bet! I got a full house today, but will run the full gambit in the next day or two.
NPLC 10, 5, 1, 0.1 at ranges 10, 1, 100mV, 1 sec polling:
ftp://xdevs.com/k2010/ (http://ftp://xdevs.com/k2010/)
how should i "look" at this to understand my DMM?
should the error limiters be flicker FM or PM? these are all FM.
i converted all to nV scale so there is no decimal points to consider on the Y axis, hmmm not enough samples to reach 1000 (i think needs about 2048 samples)
as kleinstein pointed out before, the K2015 is at the limits of its "anti noise" mod. now what would happen if the 2010 is modded?
OK here are results for a K2182A.Alan, can you share the raw data taken with K2182? Or take some new files for a few ranges, longer is better.
Alan
Overall, the performance seems to be slightly worse than DMM7510.
i converted all to nV scale so there is no decimal points to consider on the Y axis, hmmm not enough samples to reach 1000 (i think needs about 2048 samples)
as kleinstein pointed out before, the K2015 is at the limits of its "anti noise" mod. now what would happen if the 2010 is modded?
I'm happy to do longer runs.
I've not looked in detail, but I'm more than willing to mod my 2010. (I need more DMMs, too much stuff to log) :scared:
Point A - This y-axis value is the standard deviation of noise for any one single measurement point.
Point B - Averaging over the time spans along the decreasing slope corrects noise which oscillates quickly.
Point C - Eventually, you average enough that the fast-oscillating noise is mostly corrected for. This minimum has both an X and Y value of interest.
Point D - Noise which oscillates over longer time frames begins to influence bigger groups of averaged data.
Looking at the zero point noise in the 10 V range is a little odd point to test, as for a real signal near zero one would often use a smaller range.
Looking at the zero point noise in the 10 V range is a little odd point to test, as for a real signal near zero one would often use a smaller range.
This is generally true, but we are talking about 7.5-8.5 digit meters, where the whole point is to resolve a small fractional signal. Otherwise for small signals near zero one can always just use a pre-amplifier. For 10V range, 10^(-7.5)=0.03 ppm=300 uV, which is exactly where DMM7510 is starting to behave funny. So one can say it just barely satisfies its specs of giving a result to 7.5 digits. Actually it has rms noise specifications in the datasheet and the measurements that have been posted here are right on the edge, some are results are OK but some are slightly worse than the datasheet specs.
With a working AZ mode, the noise curve should go down even for long times even beyond the 300 seconds. There is not need to choose an integration time near the minimum of the curve - one can always do later averaging on the data. Most modern DMMs get the longer (e.g. > 100 PLC) integration times from averaging anyway.
The use of faster sampling is more question of data rate and memory / file size - not a big problem anymore. So even with longer time logging one can use quite a fast sampling and do filtering / averaging as needed later. Also there often is no choice of time scale - it is set by the experiment.
Also keep in mind that with real, non zero readings, there will be additional noise from the reference. This is not captured in the thread so far - but it can be quite important at a slower time scale. Most refs. show quite some flicker noise, so the curve including the reference will go up after some time. So for comparison one could include the noise of typical refs (e.g. LM399 and LTZ1000). Looking at the zero point noise in the 10 V range is a little odd point to test, as for a real signal near zero one would often use a smaller range.
**edit, but looking at Tin's 7v log "7v_3458_nplc200_tin_goodA3.csv". we see that the noise is now an increasing slope. by using allans variance, we can see that in order to resolve 1uV, we should sample below 16seconds. does this make metrological sense?
**edit, but looking at Tin's 7v log "7v_3458_nplc200_tin_goodA3.csv". we see that the noise is now an increasing slope. by using allans variance, we can see that in order to resolve 1uV, we should sample below 16seconds. does this make metrological sense?
Hello,
I guess there is something wrong with the measurement setup (or the alan deviation calculation)
I know that Frank has usually below 200nV standard deviation when measuring a LTZ1000 with his HP3458A at 100NPLC and AZERO on (>=4 seconds)
And yes: it makes no sense with a 3458A to average more than around 10 measurements.
(the X-scale is in measurements so a 1 corresponds to 5 seconds with triggered measurement).
Your LTZ/3458A plot begins with 400-500nV which is far too high.
with best regards
Andreas
7v_3458_nplc200_tin_goodA3.csv
A relatively easy to reproduce finite ref voltage might be a pack of NiCd cells (e.g. 6 to 8 cells to get 7.4 to 9.8 V.
Hello Frank,
Instead, such long termed measurements with equidistant measurements, analysed by the Allan Distribution, reveals the different stability effects, as you can already identify in the diagram.
Frank
Suggest to use recent 7V LTZ test.
Hello Frank,
Instead, such long termed measurements with equidistant measurements, analysed by the Allan Distribution, reveals the different stability effects, as you can already identify in the diagram.
Frank
Do you have the Allan diagram for this measurement, or can you provide the raw data?
With best regards
Andreas
The time scale seems to be unstable.
The time stamps have 6-10 seconds difference between the steps.
I think for allan deviation you should use equal time stamps.
Yep. Latter one. Dammit. xlsx not allowed. xls too big. therefore csv data. Sorry.No csv format, therefore txt. Rename it, please.
Frank
would my assumption be correct that this integration time is around 25s ? base on the the first slight dip at tau =5?
then what about the huge dip going on at tau =700, do you know what to make of that? this is all so new :-/O
That artefact at tau=700 will be related to that initial drift on the first 2h, when the 3458A inside the room had at first to stabilize.
I was told by someone that Plotter and Alavar seem to show different results in Allan Variance.
Andreas, have you performed a conformance test?
Here we go, 1.2 KOhm WW Ohmite 41 (https://www.digikey.com/product-detail/en/ohmite/41F1K2E/41F1K2E-ND/823174) resistor on preamp input, gain change to 10K.
Noise still very low, ~15nV/pk-pk, if my math is right.
Perhaps I should move this discussion into separate thread?
hmmm i think the csv format saved some special characters. due to conversion from chinese character?i run EZGPIB in XPMODE(English version ) to record data.
anybody else with keithley want to try a base NPLC of 2 / 3 / 4 and its effects on the noise plateau (in allan variance plot?). ie : NPLC4 x 25 repeating ave to get nominal 100NPLC?Doing extra averaging (e.g. 25 times 4 PLC to get a simulated 100 PLC) does not help for the Alan variance plots. The exactly same data would be in the curve with the single readings (4 PLC) - it is just a different program to do the average, and you get some extra in between point if you use the data directly.
anybody else with keithley want to try a base NPLC of 2 / 3 / 4 and its effects on the noise plateau (in allan variance plot?). ie : NPLC4 x 25 repeating ave to get nominal 100NPLC?Doing extra averaging (e.g. 25 times 4 PLC to get a simulated 100 PLC) does not help for the Alan variance plots. The exactly same data would be in the curve with the single readings (4 PLC) - it is just a different program to do the average, and you get some extra in between point if you use the data directly.
The Keithley 2015 seems so show the same strange (Keithley typical ?) plateau. So if it supports modes like 2,3,4,5 PLC you are free to take the data (a little longer than the old curves). At least the 10 V data should be rather similar to the stock 2000 / 2015.
The digital resolution of DMM7510 is shown here https://www.eevblog.com/forum/metrology/dmm-adc-noise-comparison-testing-project/msg1081650/#msg1081650 (https://www.eevblog.com/forum/metrology/dmm-adc-noise-comparison-testing-project/msg1081650/#msg1081650)
It is about 0.0014 ppm (I zoomed in, but the histogram looks gaussian on larger scale).
Has anybody tried to analyze the resolution of the data being output?
Assume they are using single precision floating point arithmethic on the DMMs with 24 Bit resolution mantissa....
In this case it makes a difference if you calculate the averaging on DMM or on PC (with double precision).
When I have a look at Blackdogs HP34461A noise data in 10V-range then suddenly at 10mV the resolution seems to change ...
with best regards
Andreas
Hello,I was told by someone that Plotter and Alavar seem to show different results in Allan Variance.
Source?
Significance?Andreas, have you performed a conformance test?
Why should I?
Do you make conformance tests with every standard tool that you use?
With best regards
Andreas
Cannot believe that there is no noise??
Hi,
im trying to get the python-script "pars_noise_sd.py" which TiN wrote to work, but with the downloaded Python Interpreter 3.6 its just shows me the error:
Python 3.6.1 (v3.6.1:69c0db5, Mar 21 2017, 18:41:36) [MSC v.1900 64 bit (AMD64)] on win32
Type "copyright", "credits" or "license()" for more information.
>>>
========== RESTART: C:\MyMeasurements\HP34420A_1\parse_noise_sd.py ==========
| Multimeter | Range | NPLC | Counts | Sq.sum | Average | SD | SD,uV |
Traceback (most recent call last):
File "C:\MyMeasurements\HP34420A_1\parse_noise_sd.py", line 15, in <module>
o.write ("|Multimeter|Range|NPLC|Counts|Sq.sum|Average|SD|SD,uV|\r\n")
TypeError: a bytes-like object is required, not 'str'
c:\__\code\py_parsesd>parse_sd.py
| Multimeter | Range | NPLC | Counts | Sq.sum | Average | RMS | RMS,uV |
| HP34420A | 10 | 100 | 74 | 0.00000000 | 1.051549E-07 | 1.698011E-07 | 0.17 |
Here is the comparison of DMM7510 and 34465A for finite input. I used a 10.24 V 7Ah (almost dead) lead battery from a UPS supply and a 3.13 V (primary, moderately used) Li CR123A battery from a wireless alarm sensor. For lead battery, I removed linear self-discharge trend. For Li battery, just found a quiet temperature spot.
(https://www.eevblog.com/forum/metrology/dmm-adc-noise-comparison-testing-project/?action=dlattach;attach=279017)
As might be expected, at finite voltage 34465A does not perform as well, probably due to limitation of the voltage reference. It would be best to compare 34470A to DMM7510 in this case.
@dvdput: Thanks for posting the data! Looking at the file on 10V scale the digital resolution is 3 uV. This is much worse than 34465A. If there is no way to change this setting it points to a clear superiority of 34465A at a smaller list price. It would be nice to add some of this information to the DMM comparison table, so people can decide which meter to buy with information that is often not stated on the datasheets.
I was considering buying it, is this real problem?
Is it software or hardware problem? Didnt Keithley fix it with new firmware patch or something?
Doesnt that graph I quoted show the problem only exist with shorted inputs?
This leads me to believe, it might be hardware related and can not be fixed by software.
My point is,as a person that want best dmm to measure 10V,I should not be put off by the poor 0V noise of 7510 since at 10V its better than keysight,or I am wrong?
My point is,as a person that want best dmm to measure 10V,I should not be put off by the poor 0V noise of 7510 since at 10V its better than keysight,or I am wrong?
If your application is specifically to measure 10V and if you are comparing DMM7510 to 34465A, which is about 1/3 of the price, then indeed DMM7510 is better.
I recently got a 34470A, so I will run at some point a direct comparison DMM7510 to 34470A. A few other people here can also do it at 10 V. Would be good to through in a 3458A as well.
This leads me to believe, it might be hardware related and can not be fixed by software.
I doubt the AZ issue is HW related. The software issues were fixed (They still haven't fixed the web interface issues, at least it wasn't noted in the changelog) fairly quick because once IDed and reproducible that stuff is usually easy. The AZ issue on the other hand would require the *right* guy at Keithley to research and study what is going on. The difficulty here might also be in the fix, it would alter the behavior of the instrument and might be an issue for some customers, requiring re-certification or production line changes.
I suspect we will never get any traction on this issue. :(
I have both instruments and like them a lot.
That would be great! I am currently deciding between 34470A and 7510,any test comparing the two directly would be very appreciated.I would also like other measurements tested,not just DCV,also ACV and DCI,ACI,resistance 4 wire and capacitance
The 7510 has a very interesting warmup graphYes, I remember noticing the steps in the voltage when the temperature is changing quickly even when its reading zero. I am not sure if its an ideal behavior, but they probably do a more aggressive temperature correction than Keysight.
How long does the 7510 ACAL last anyway,34470 is around 15 seconds if I remember correctly.I have read that 7510 fan is loud and 34470 is quiet,is that true?
Can you leave the instruments recording 10 V for a few hours at 10 PLC and post the data?
This looks good, similar to other measurements. The long-term stability is quite good.
What would be most interesting is to take 7510 and 34470 data at the same time to compare them directly.
Question: What noise would one expect, if DMM measures its own voltage reference in 10V range?
When measuring it's own reference the ADC will see some of the reference noise, but not all. What exactly depends on the ADC type. Especially the very low frequency part is well suppressed. There may be a significant contribution (could very well be amplification) from some higher frequencies (where the modulation in CB ADCs happens). Of cause the amplifier part is still there.
AFAIK the Prema meters use an AZ OP at the input. This could be a significant contribution to the noise in the lower voltage ranges, but it usually is not for the 10 V (or similar) range. Here changing the OP might be possible (e.g. LTC1050/ICL7650 to LTC1052/ICL7652). However with AZ OPs it is usually a compromise between bias current and voltage noise. The very lower noise AZ OPs usually have to much bias and maybe to much current noise too.
The Prema meters use an special ADC chip - so nothing to improve there. There might be a small chance to improve reference filtering (to reduce the higher frequency noise part). At least a few meters (e.g. Keithley 2001 AFAIK) seem to have skipped on this rather simple option. However I am not sure on how much that contribution is - it may not be that much. Looking in detail at the noise source could be interesting, but would be more likely worth a separate thread - if it leads to significant results they would be interesting in this thread too.
Question: What noise would one expect, if DMM measures its own voltage reference in 10V range?
I'm currently observing the reference voltage on my Prema 5017 by itself and I'm the opinion that the noise is rather high.
Here is a bit more data on direct comparison of DMM7510 and 34470A. In my lab there is often a pronounced temperature oscillation of a few tenths of a degree with a period of 1000 sec. One can see nice Fourier peaks in the temperature and the voltage. For these tests the meters are placed on a lab bench with plenty of space around each one, while the battery is well thermally insulated. Under these conditions, Keysight 34470A has about a factor of 2 higher sensitivity to temperature changes compared to Keithley DMM7510. That is the origin of the peak in the Allan deviation around 500 sec which drops down at 1000 sec because the temperature changes are fairly periodic.
(https://www.eevblog.com/forum/metrology/dmm-adc-noise-comparison-testing-project/?action=dlattach;attach=363179)
(https://www.eevblog.com/forum/metrology/dmm-adc-noise-comparison-testing-project/?action=dlattach;attach=363185)
(https://www.eevblog.com/forum/metrology/dmm-adc-noise-comparison-testing-project/?action=dlattach;attach=363183)
Here is the Allan variance of Martin's Keithley 2010 for 10V range 1 plc data - it has exactly the same bump as DMM7510! This is the clearest evidence yet that the Autozero problem is deep inside their algorithm and applies to all meters, not just DMM7510. No wonder they have trouble fixing the problem.
The 2001 meter is different from most other meters, as it uses a short time time reference (zener-diode on the ADC board) for the ADC and long time reference (LM399). So there somehow needs to be a regular extra measurement of the long time reference (LM399) - this could be as frequent as after every reading. There are other options, like switching between the AZ and 7 V reading - thus requiring some averaging for the AZ readings as I observed.
Some time ago, I debugged the ADC in K2001 (at first I thought it was faulty - too noisy). When I connected test leads to a node on the ADC board, there was often an immediate shift in readings - a few tens of ppm. Of course, this is not so surprising since conditions in the ADC circuitry were changed by attached test leads. What surprised me was K2001 reaction - with test leads still connected it returned to the initial reading very slowly and reluctantly. IIRC, the return to the initial value consisted of several discrete steps (it was not definitely smooth).Using some averaging for the gain calibration is OK, as this can reduce the noise, especially ADC noise and higher frequency noise of the long term reference. Averaging determines the cross over from the long term reference to the short therm reference at the ADC. However averaging for the zero reading used for the offset compensation (AZ) is not such a good idea: it reduces the higher frequency noise, but on the back side it adds low frequency noise, that is higher due to 1/f noise. Ideally the AZ readings can suppress much of the low frequency noise just like a chopper amplifier. However this does not work well anymore when the zero readings are averaged. This seems to be a problem with quite a few of the Keithley meters.
I suspect AZ calibrates zero/gain of the ADC and averages these calibration values over a given time period. Therefore several measurement cycles are needed to adapt to a new state of the ADC circuitry. Using averaged zero/gain calibration values rather than actual ones might lead to excess of noise in K2001 ADC. (AZ might not be able to seamlessly compensate the drift since it looks too much to the past due to the averaged values.)
...
The master reference (LM399) is used to calibrate the whole multimeter.No. The master reference is used to calibrate the ADC FS on a periodic basis. K2100 does the same thing via the same DG408 MUX.
The master reference (LM399) is used to calibrate the whole multimeter.No. The master reference is used to calibrate the ADC FS on a periodic basis. K2100 does the same thing via the same DG408 MUX.
Is there ootb script/tool for 3458A and Solartron 7081 for Linux/RPI awailable?
Or at least sourcecode, so that it is easy to derive script?
At least for me this is surprising, because theorie claims that 100 samples should give "trustworthy" results for SD :-//
We want to compare the ACRMS/SD of shorts for different DMMs at given PLC and range.
What would be a good method to do this?
For me it seems that this method gives large spread and for that reason even comparing meter to itself seems not appropriate.
...
Usually it's completely sufficient to take 10 .. 16 samples to get a good estimate for the quantity to be measured, and also that implies that the StD is sufficiently 'stable'.
Taking more samples to 'improve' the StD is counter productive, as you will get instabilities of higher order into your measurements, e.g. mid- and long term drifts.
...
As you cite my measurements, I just want to refer to the Allan Deviation method, where you get a good picture of instabilities or noise over different timescales.
...
If the noise is just white noise, relatively short sets of readings give good estimates for the standard deviation. However if there is some extra 1/f or popcorn noise or drift or a other superimposed signal the RMS calculation can fluctuate and different lengths may show different values. In this case the Allan deviation plot may be more helpful than just the standard deviation. A single number is just not sufficient to characterize complex noise.
So I would interpret the fluctuations seen in the stD calculated over 100 samples each as an indication that there is not just white noise.
...
RMS noise and StD share basically the same formula, so under some precautions, like observation of the different noise sources, the StD gives a good estimate for the noise figures, as I have demonstrated with my diagram for apertures ranging from 1.4µs to NPLC of 1000.
I can't observe, that there is a large spread, compared to the hp specification, and also within the whole graph.
Please also take notice, that such measurements are always plotted on a logarithmic scale, so small variations do not play a role.
...
| rolling SD(10) | rolling SD(100) | rolling SD(1000) | SD(16154) | |
| multiple runs white noise | ~+-50...100% | ~+-20...30% | ~+-5...10% | 100nV <+-1% |
| original dataset | -72% +80% | -26% +26% | -7% +13% | 100nV |
We want to compare the ACRMS/SD of shorts for different DMMs at given PLC and range.
Who is 'WE'? Plural Majestic? :-//
...
I also do not understand, which theory you mean, which gives an idea about the 'trustworthiness' of the StD.. sounds very strange to me.
...
Reference, FLUKE: Applying Measurement Uncertainty to Digital Multimeter and Clamp Meter Calibration
http://download.flukecal.com/pub/literature/webinar-uncertainty-presentation-Dec%202011.pdf (http://download.flukecal.com/pub/literature/webinar-uncertainty-presentation-Dec%202011.pdf)
In contradiction for large sets the ACRMS/SD may be dominated by other noise sources, as you already stated.
I am wondering if it would be appropriate to use rolling ACRMS/SD with short sets on a large dataset and take e.g. the Mean of all rolling ACRMS/SD?
Intention is to have a high-pass filter to get rid of probably dominant LF Noise Sources (Drift, TC, popcorn-noise?) whilst maintaining good approximation of the remaining mostly white noise part.
Clearly there is not one number to deal with "complex" noise, but if it is possible to separate appropriate into a couple of numbers for different noise types and other influences, this would have value.
The shorted DMM seems to have mostly white noise, but you are right, for deeper insight the Allan deviation would be helpful.
*IDN?
HEWLETT-PACKARD,34401A,0,7-5-2
cal:count?
+42
cal:str?
"15 FEB 1996 26.2C"
(Why 26.2C? Who knows?)*RST
*CLS
CONFIGURE:VOLTAGE:DC 10V,MIN
VOLTAGE:DC:NPLC 1
SENSE:DETECTOR:BANDWIDTH MAX
SENSe:ZERO:AUTO ON
INPUT:IMPEDANCE:AUTO ON
TRIGGER:SOURCE IMMEDIATE
SAMPLE:COUNT 50
Then READ? in a loop.Integration time Resolution
1 NPLC 0.000003 x Full-Scale
10 NPLC 0.000001 x Full-Scale
100 NPLC 0.0000003 x Full-Scale
Agilent 34410A noiseThis is an awfully long thread and I'm sure it has been explained before, but perhaps for readers as lazy as me, it might be worth to restate (every 10 pages or so ;-} how this measurement was made. Variations in measurement less than 0.1 ppm on a 6.5 digit meter are worth expanding on, methinks.
10VDC, 100NPLC, Auto-Zero, Fluke 4W short.
(https://ampnuts.com/wp-content/uploads/2021/03/34410A_raw.png)
[..]
V7-54/2 6.5 DMM developed in MNIPIThe data somehow have insuficient resolution. There is still some variation, but just +0 and -0. So one would need to change the data format. One may have to use shorter integration to get useful data, that are no longer limited by ouput quantization.
20V range, 2.56s integration time.
Sorry, cannot calculate Allan variance for this dmm. :)
V7-54/2
1 volts range, 2.56s integration time. About 34 hours log:
shorter integration.Shorter integration time for this type ADC = less resolution.
0.2 V range is more limied by the amplifier and not the ADC's quantization.You right!
Amplifier is little bit noisy, but have very low input bias current (~0.07pA).Is there a schematics or other details? What transistor is at the input? How are the protection circuits made?
Amplifier is little bit noisy, but have very low input bias current (~0.07pA).What transistor is at the input? How are the protection circuits made?
You defeated me. :oOops :) Have you measured the input bias current? ::)
Keysight B2985A noise.
2pA range, 100NPLC, input closed with dust cap.
The circuit looks strange for modern times - still using a photoresistor chopper, at least allready with LEDs and no neons. less than 1 pA bias suggests that there is some adjustment/compensation of the current of some kind (should be possible through the LDR chopper).This DMM start development in late 80, and production start in about 1991-1992 year.
The curves for the 3458 and 2182 DMMs show quite some dips at 20 ms and 40 ms integration. This suggests that there is quite some residual hum in the signal, and not just noise.inputs are just directly shortened with 0 Ohm, what else could i do.
The curves for the 3458 and 2182 DMMs show quite some dips at 20 ms and 40 ms integration. This suggests that there is quite some residual hum in the signal, and not just noise.Keithley 7510 shows the same behavior.
The amplitude goes down at 20 ms, but not much at 10 ms integration. So the background is more 50 Hz hum and not 100 Hz. I would suspect magnetic coupling, either from the DMM internal transformer or other transformers or similar sources of a magnetic field. External fields could be shielded with some steel or just reduced with more distange, or a less susceptible position. For the 3458 the connection at the guard terminal can also make a different. Chances are it should be connected to COM for the noise test.The curves for the 3458 and 2182 DMMs show quite some dips at 20 ms and 40 ms integration. This suggests that there is quite some residual hum in the signal, and not just noise.inputs are just directly shortened with 0 Ohm, what else could i do.
all the questions to voltmeter manufacturers why PSRR is that bad, so it is visible with shorted inputs when aperture time is not an integer number of PLC.
The amplitude goes down at 20 ms, but not much at 10 ms integration.I would suspect magnetic couplingyes, for poor PSRR rectified 100Hz should be present, but
What is the data rate?Data rate is 3sps.
Do you know how to calculate the standard deviation?Stdev=1.2nV
10hours noise & stability of 33years old V2-38 nanovoltmeter:could you please share raw data as well?
10uV range no filter no dumping. Plotted raw data.
could you please share raw data as well?No problem!
Measurements were made on the range of 10 μVJust updated the plot,
Mine data from ad7461a.What is the y-axis dimension?
What is the y-axis dimension?Since no math applied, its in lsb of range, ie 10uV for 10V, 1uV for 1V, 0.1uV for 100mV, and cause max readings are 1e6, it become ppm of range.
The Allan deviation is a useful form to show the result, as one can also see how good one could get with averaging..Thus my above measurement says I can go for 5minutes with averaging at that range.