....
It's alive!!!!
I still need to buy more solid-state relays to populate the rest of the board but what's there seems to work flawlessly (so far), silent and fast. Since I was trying to keep the cost as low as possible (you can tell from the all DIY PCB board), the relays are not the best, the on state resistance of each channel is around 2 Ohm. But it's not a big deal as I have plenty of channels to use kelvin connections if needed. A $12 Atmega32u4 based board is handling all the logic.
(top board: Keithley 2000-Scan with wires attached for protocol sniffing)
(bottom board: DIY 20-chan solid state scan card)
It's alive!!!!
Feature request:
1) A fast way to store the stats of the measurement to USB, I know you can use a screenshot but then you need to store screenshots. You can also not just copy it in a excel file.
Two options:
A) When you take a screenshot with home+enter also write a second file, a csv with the same name.
Beta storage service (initialstate): Anyone using this?
https://www.initialstate.com/keithley/
Beta storage service (initialstate): Anyone using this?
https://www.initialstate.com/keithley/
Feature request:
1) A fast way to store the stats of the measurement to USB, I know you can use a screenshot but then you need to store screenshots. You can also not just copy it in a excel file.
Two options:
A) When you take a screenshot with home+enter also write a second file, a csv with the same name.
B) Make it possible to link a script to a button, like maybe home+trigger runs a pre-selected script.
and let the script do the needed actions.
(This is maybe a feature on its own that could be useful for all kind of situations.)
2) A feature request for the current measurement mode, show the voltage drop! (burden voltage isn't a second measurement) Now I have to check to be sure it's low enough. (although if not much work I choose my own resistor value)
3) For math y=mx+b, support entering 2 points (like: 4mA=0 and 20mA=7) instead of entering m and b and let it calculate m and b. (maybe this should be a script)
Also an option to change the 'X' to an 3 char that has meaning. (sometimes you forget what you were displaying after reloading the settings)
1) Hmm, so a csv of just the buffer stats? We have thought about using buttons as shortcuts for scripts before but ultimately decided not to since the buttons are supposed to be universal across instruments. Scripts are already pretty easy to access with the drop-down menu too, yes? Or not fast enough for you?
2) The DMM6500 doesn't have any internal way to find out what the voltage drop is. The shunt resistors are internally calibrated, but there's also the path resistance which is pretty variable and can't really be measured by internal processes. BUT, you can use the secondary measurement feature to measure voltage drop by shorting INPUT HI to AMPS, that would measure the internal voltage across the current leads. If you choose the 1A or 3A range, there won't be any relay clicking on <100V ranges. OR, you could go a step further and measure the voltage drop out to your DUT by connecting INPUT HI to the high side of your DUT. You could remove the low side path voltage drop by using the rel feature between INPUT HI and your DUT low terminal before swapping to measure voltage between INPUT HI and your DUT high side. Does that make sense? I can draw the process out if you want.
2) The DMM6500 doesn't have any internal way to find out what the voltage drop is. The shunt resistors are internally calibrated, but there's also the path resistance which is pretty variable and can't really be measured by internal processes. BUT, you can use the secondary measurement feature to measure voltage drop by shorting INPUT HI to AMPS, that would measure the internal voltage across the current leads. If you choose the 1A or 3A range, there won't be any relay clicking on <100V ranges. OR, you could go a step further and measure the voltage drop out to your DUT by connecting INPUT HI to the high side of your DUT. You could remove the low side path voltage drop by using the rel feature between INPUT HI and your DUT low terminal before swapping to measure voltage between INPUT HI and your DUT high side. Does that make sense? I can draw the process out if you want.
1) Hmm, so a csv of just the buffer stats? We have thought about using buttons as shortcuts for scripts before but ultimately decided not to since the buttons are supposed to be universal across instruments. Scripts are already pretty easy to access with the drop-down menu too, yes? Or not fast enough for you?
1) Yes just the stats also cursors if there are any, can we write a custom csv file to usb with scripts?
Fast, well would be easy if it was present in the same screenshot function so they match an I guess this is little work or risk for firmware.
2) The DMM6500 doesn't have any internal way to find out what the voltage drop is. The shunt resistors are internally calibrated, but there's also the path resistance which is pretty variable and can't really be measured by internal processes. BUT, you can use the secondary measurement feature to measure voltage drop by shorting INPUT HI to AMPS, that would measure the internal voltage across the current leads. If you choose the 1A or 3A range, there won't be any relay clicking on <100V ranges. OR, you could go a step further and measure the voltage drop out to your DUT by connecting INPUT HI to the high side of your DUT. You could remove the low side path voltage drop by using the rel feature between INPUT HI and your DUT low terminal before swapping to measure voltage between INPUT HI and your DUT high side. Does that make sense? I can draw the process out if you want.2) Hmm I'm going to give that a try, but I don't need to see the exact drop but more like a warning of expected max drop like 2 digits accuracy. Like text in a new tab you update when going there "The burden voltage is about 0.23V at max current in the buffer and 0.52V at full range."
I assume it's possible in a script, maybe with your own measured values.
2) The DMM6500 doesn't have any internal way to find out what the voltage drop is. The shunt resistors are internally calibrated, but there's also the path resistance which is pretty variable and can't really be measured by internal processes. BUT, you can use the secondary measurement feature to measure voltage drop by shorting INPUT HI to AMPS, that would measure the internal voltage across the current leads. If you choose the 1A or 3A range, there won't be any relay clicking on <100V ranges. OR, you could go a step further and measure the voltage drop out to your DUT by connecting INPUT HI to the high side of your DUT. You could remove the low side path voltage drop by using the rel feature between INPUT HI and your DUT low terminal before swapping to measure voltage between INPUT HI and your DUT high side. Does that make sense? I can draw the process out if you want.
Tried this measurement method:
Seems to be a difference of 37m\$\Omega\$ less, I'm losing a bit of wire there.
edit: adding 100mA and 10mA range, it isn't working as expected. (relay switching)
The discontinuity happens because voltage measurements happen while the current range relay is in the 1A/3A position. So if the relay isn't already in that position it will be forced there. I'm not totally sure all the reasons that position is required, but I believe part of it is to prevent noise from reaching the voltage measurement circuitry.
So anyway, it's best to use the 1A/3A ranges if you want to continuously measure burden voltage with this method.
Did you use any filter on dmm6500? What's the input impendance of both? Try to use "repeat, count 10", input z 10M , 5 NPLC
Did you use any filter on dmm6500? What's the input impendance of both? Try to use "repeat, count 10", input z 10M , 5 NPLCNo filter, just 1PLC it's DC current.
The DMM6500 spec says 10k so that is 1/1000 000 of the big resistor or it's measuring 10µV. STD: 0.455µV
I tried:
https://github.com/tektronix/keithley/blob/master/TSP_Apps/Resistance_Tolerance_Meter.tspa
- When starting I get an error, like not correctly initialized.
- When I exit the app the custom buffer stays the selected buffer, maybe this should be set back to the default buffer to avoid this next error.
- I got a few bad reading (high impedance) due to bad contact, so had to press retry but if two follow each other I will not be able to do that.
- It also shows rear terminals in the csv file while I used the front.
Not related to this app, can I make saving the measurements so that the column time is always the first column and the measured value always the second? (makes it easier in excel)
fileVar = file.open("/usb1/savedbuffer.csv", file.MODE_WRITE)
file.write(fileVar, "Relative Time, Reading\n)
for i = 1, defbuffer1.n do
file.write(fileVar, defbuffer1.relativetimestamps[i]..","..defbuffer1.readings[i].."\n")
end
file.close(fileVar)