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Author Topic: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter  (Read 15337 times)

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Offline evava

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #200 on: July 17, 2017, 07:42:59 PM »
Guys, calm down.
I like all your answers, they explain many things.
But, IMHO the strongest point of this $19 meter is 1uV resolution, not any of his Amp range. No need to discuss Amp ranges so deeply.

When you look at Wytnucls multimeter spreadsheet, you find just few meters with 1uV resolution.
What I am missing at this meter is logging (whatever RS232, USB, BT) and I think that somebody already enabled logging on this chipset.

That would be something, 1uV resolution meter with logging for $19 - that would become surely UT61e killer.

If there is someone who can do it, please do it!
 
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Online plazma

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #201 on: July 17, 2017, 07:46:55 PM »


.......
What I am missing at this meter is logging (whatever RS232, USB, BT) and I think that somebody already enabled logging on this chipset.

That would be something, 1uV resolution meter with logging for $19 - that would become surely UT61e killer.

If there is someone who can do it, please do it!

In the AN8002 model the UART TX signal was not bonded. I'll check the AN8008 when I receive it.
 

Offline Gandalf_Sr

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #202 on: July 17, 2017, 08:12:12 PM »
I'll chip in on the how best to compare the current reading of 2 meters, one of known accuracy, and the other being compared.  Kirchoff's second law says that sum of currents flowing into a node is equal to the sum of the currents flowing out of that node; if you only have 2 meters in series then the law says that whatever current flows is the same in both meters.

The only way to do a comparison test (IMHO) is to connect the 2 meters in series.  Then I would connect a supply from a power supply and use current limit to get close to the value I want to test, say 1 Amp.  Now wait until the readings are steady and record both values. Next do the math to say how accurate is the one under test compared to the good one.

You can't set up the constant current supply and then test, switch meters around, and test again (unless you have a calibrated current source like a Druck). The resistances presented to the supply by a current meter are so low that the resistance of the test lead and banana connectors is very significant and it will likely change just by disconnecting and reconnecting.  You can talk about burden voltages all day but, as Mark says, who cares? We're measuring current.  An expensive meter will have a lower burden voltage than a cheap one but so what?  What matters is that I'm measuring the same current that flows through both meters.
 
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Online Fungus

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #203 on: July 17, 2017, 08:51:26 PM »
Guys, calm down.
I like all your answers, they explain many things.
But, IMHO the strongest point of this $19 meter is 1uV resolution, not any of his Amp range. No need to discuss Amp ranges so deeply.

The poor mA resolution is only a problem if your life plan is "own exactly one multimeter".

We all know this is 100% impossible so why argue?
 
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Online EEVblog

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #204 on: July 17, 2017, 08:55:06 PM »
Guys, calm down.
I like all your answers, they explain many things.
But, IMHO the strongest point of this $19 meter is 1uV resolution, not any of his Amp range. No need to discuss Amp ranges so deeply.

The vast majority of electronics works on mA, not uA.
This meter fails to cover the most common current ranges in electronics design with any degree of decent resolution.
 

Online alm

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #205 on: July 17, 2017, 09:02:28 PM »
If anything, skipping the amps range would make more sense to me. Circuits where you need both µA/nA and µV are unlikely to need amps ranges. The exception might be HVAC, but for some reason this does not strike me as an HVAC meter ;).

I guess they wanted to claim 10 nA to 10 A in their marketing material.
 

Online Fungus

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #206 on: July 17, 2017, 09:03:59 PM »
Guys, calm down.
I like all your answers, they explain many things.
But, IMHO the strongest point of this $19 meter is 1uV resolution, not any of his Amp range. No need to discuss Amp ranges so deeply.

The vast majority of electronics works on mA, not uA.
This meter fails to cover the most common current ranges in electronics design with any degree of decent resolution.

Maybe they're planning to release another one in a couple of months* with 10mA range and temperature. 

Double the sales! :popcorn:


(*) Or after the sales of this one die down.

 

Offline Gandalf_Sr

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #207 on: July 17, 2017, 09:39:28 PM »
The vast majority of electronics works on mA, not uA.
This meter fails to cover the most common current ranges in electronics design with any degree of decent resolution.
I'm with Dave on this one, I'd much rather see the 10A range replaced by a usable mA range.  Can't this meter be hacked to do that, maybe with a shunt resistor change?
 

Online alm

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #208 on: July 17, 2017, 09:46:09 PM »
Sure, if you spend another $20 on a new shunt :P.
 

Offline Gandalf_Sr

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #209 on: July 17, 2017, 09:50:12 PM »
Sure, if you spend another $20 on a new shunt :P.
OK, the challenge has been made!  All I have to do is wait for my meter to arrive on the slow boat from China...   :=\

[EDIT]  What's the resistance of the 1A shunt?  If it was 0.001 Ohms then I'm thinking it would be way less than $20 for a 1 Ohm 0.1% resistor.
« Last Edit: July 17, 2017, 11:15:37 PM by Gandalf_Sr »
 

Online Fungus

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #210 on: July 17, 2017, 11:22:10 PM »
[EDIT]  What's the resistance of the 1A shunt?  If it was 0.001 Ohms then I'm thinking it would be way less than $20 for a 1 Ohm 0.1% resistor.

You can calculate it by looking at the burden voltage in the specs.

Normally it won't be a high precision resistor though. It will be medium-precision and the calibration process will cancel out the error. You'll have to rewrite the calibration in the flash memory after you swap the resistor.

 

Offline evava

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #211 on: July 17, 2017, 11:33:48 PM »
Guys, calm down.
I like all your answers, they explain many things.
But, IMHO the strongest point of this $19 meter is 1uV resolution, not any of his Amp range. No need to discuss Amp ranges so deeply.

The vast majority of electronics works on mA, not uA.
This meter fails to cover the most common current ranges in electronics design with any degree of decent resolution.

I only wanted to say, that when someone pointed out this meter has only two shunts, 100 ohms and 0.1 ohms, in that moment was clear some Amps ranges are missing. And then you showed that in your video. Thank you! Then someone pointed out even worse behaviour when measuring AC Amps, which was explained by TRMS conversion. And from that moment on we all know everything about stock AN8008 Amps ranges. We now have no need to discuss stock Amps ranges any more IMHO (except to replace highest Amps range shunt with bigger(more Ohms) shunt to lose 10Amp range for gaining other ranges which are now missing - it might be doable, for $$ obviously))
But me (and others) have other meters for that Amps ranges.

I for example have no reliable and usable meter with 1uV resolution (Fluke 289 failed entirely in that regard despite its price - next time I should read manuals more carefully - 50.000mV 0.05%+20 - ridiculous! Where is LSD digit? And really behaves in this manner! LSD changes itself randomly in the scale +-20 counts!)
I was looking forward to Dave's (Your) 121GW and now this "little gem" appeared  :)

I would like to move on to next topic, and that could be logging in my opinion.
« Last Edit: July 17, 2017, 11:36:23 PM by evava »
 

Online mauroh

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #212 on: July 17, 2017, 11:37:46 PM »
Guys, calm down.
I like all your answers, they explain many things.
But, IMHO the strongest point of this $19 meter is 1uV resolution, not any of his Amp range. No need to discuss Amp ranges so deeply.
The vast majority of electronics works on mA, not uA.
This meter fails to cover the most common current ranges in electronics design with any degree of decent resolution.
Maybe they're planning to release another one in a couple of months* with 10mA range and temperature. 
Double the sales! :popcorn:
(*) Or after the sales of this one die down.

I'm with evava!! If this nice toy will have serial output and temp measurement I'll buy 2  ;D
I don't want wait the next model, where is the hack!!!  :popcorn:
Mauro

Offline stj

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #213 on: July 18, 2017, 02:20:23 AM »
In the AN8002 model the UART TX signal was not bonded.

has that been verified on more than one meter??
 

Online matura713

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #214 on: July 18, 2017, 04:37:47 AM »

If this nice toy will have serial output and temp measurement I'll buy 2  ;D


go back to my previous posts here where with few other members we were discussing information from a Russian forum : temp measurement is simple EEPROM hack - already made and confirmed as working by the Russians - there are even Russian sellers that already sell AN8008 hacked with the temp measurement enabled. As far as the Serial Output goes - if pin 20 of DM1106EN is not used (not connected) on AN8008 board, then it's EEPROM hack to enable the output plus maybe 3 USD for parts (photo-diode, photo-transistor, 100R resistor, 1K2 resistor and UART to RS232 board that are available cheaply). in fact, at least to me the only known DM0660/DM1106EN-based DMM that is not hack-able to add Serial Output is UT139C, as they use pin 20 of the chipset for another purpose.

[EDIT] and for completeness as i am sure someone will ask, here are more details. All credits goes to respective users in "kazus.ru" who shared the information:

* EEPROM address 0xFA, bit 1 is the UART enable/disable bit - that's documented in the datasheet as well:

link click here

as it's activated/deactivated with "a long press on REL button" and there is no such button on AN8008, i guess adding REL button would be similar process of how that is done on VC921:

http://www.eevblog.com/forum/testgear/hacking-the-victor-vc-921/

* EEPROM address 0xAF changed to 0x13 adds Celsius to mA range
* EEPROM address 0xBF changed to 0x15 adds Fahrenheit to mA range

that means, when on mA range and press SELECT, it goes DC, AC, Celsius, Fahrenheit, see the picture here:

link click here

on the picture in Russian it says "BONUS: temperature measurement".
« Last Edit: July 18, 2017, 05:37:36 AM by matura713 »
 
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Offline Kalvin

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #215 on: July 18, 2017, 05:31:15 AM »
Guys, calm down.
I like all your answers, they explain many things.
But, IMHO the strongest point of this $19 meter is 1uV resolution, not any of his Amp range. No need to discuss Amp ranges so deeply.

The vast majority of electronics works on mA, not uA.
This meter fails to cover the most common current ranges in electronics design with any degree of decent resolution.

In some of the latest microcontroller projects I have been involved we have needed to be able to measure the standby current consumption in 5uA - 10uA range with 100nA resolution in order to be able to observe how the average current consumption changes when we change something in the circuit or in the software. However, when the device wakes up, the current consumption will be around 10 mA - 20 mA. This is typically a problem related to the burden voltage as the device fails to operate due to the voltage drop caused by the sense resistor inside the DMM. However, placing a low leakage and low Vf diode across the DMM inputs will take care of that problem quite nicely and limit the burden voltage to few hundred millivolts. Of course the current measurement is not accurate any more at higher currents when the diode starts conducting, but this arrangement has worked quite nicely in practice.
 

Offline Crumble

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #216 on: July 18, 2017, 07:06:40 AM »
[...]
But, IMHO the strongest point of this $19 meter is 1uV resolution, not any of his Amp range. [...]
I totally agree with that. This meter might not be entirely practical if it is your only one due to the missing ranges (and other quirks), but it has some unique features that might complement other meters if you don't have a lot to spend. Yeah, if you already have a 7,5 digit Keysight lying around you might not be especially impressed, but now I can add a µV resolution measuring option to my "lab" for just ~US$20. I have got one on its way! ;D It looks however like the designers had no good idea if they wanted it to be an electrical or electronical measurement device. Its square wave output sounds interesting, but I could not think of one single way I could implement it practically in an actual circuit due to the lack of flexibility and range. Personally, I would have inserted a third shunt in the meter and I would have used the position on the knob to select it. With dedicated temperature meters available I don't really need that as an option, but one could argue in its favour.

I already own an AN8002, and I do like it in a number of respects. It has relatively high counts for a €13 meter (this one's even better) and is quite accurate and has no pots in it. I had an old Uni-T which did, and it changed over time to be out by as much as 10% (in every range) until I found the proper pot to tweak (cause there's no documentation on that). :palm: The capacitance goes down to pF resolution and is quite fast. It is also high impendance in mV range, which can be useful for some applications. It mV range also allows for measuring current with in-circuit shunts (but you'll have to design these in, which I sometimes do), because when doing electronic work breaking the circuit open and inserting a meter with its sometimes high shunt resistances and/or long inductive leads might very well interfere. The AN8008 does have an option the AN8002 does not: manually changing ranges. I often find myself wanting to do so, but this feature lacks on the AN8002. I would have considered that a more useful feature than the present "Hold" function.

BTW with my AN8002 the diode check voltage is above the battery voltage. It puts out 3,25V while I use Ni-MH rechargable batteries that are at 2,6V (these values were measured with my unit, but might differ with other ones). It must have some kind of small charge pump in it. I must note it only delivers very low currents at this voltage, but I could light two red LEDs in series very faintly and see their forward voltage (some meters seem to put out the voltage, but just not measure it above a certain level, don't know why).
 

Online plazma

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #217 on: July 18, 2017, 07:45:48 AM »


.....
 The AN8008 does have an option the AN8002 does not: manually changing ranges. I often find myself wanting to do so, but this feature lacks on the AN8002. I would have considered that a more useful feature than the present "Hold" function....
You can add REL, RANGE & MIN/MAX buttons to AN8002.
 

Offline ocw

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #218 on: July 18, 2017, 09:56:41 AM »
I modified my AN8008 to provide single digit mA readings with 3 digit resolution.  I replaced the regular mA/A readings with the ability to measure currents below 100 mA with a XX.XX mA display.  Currents below 1A are measured with the same XXX.X mA display.  1A is now the maximum current which can be measured.

I replaced the 0.01 ohm shunt resistor for the A/mA jack with a 0.10 ohm 0.5% resistor which I had in stock.  Attached is a picture of the upgraded meter measuring 2.5000 mA current.  On the left the meter is in the uA position, the test lead is in the A/mA jack and the meter reads 2.59 (uA) [3.6% high].  On the right I've switched to the mA position but the reading has gone down to 21.9 (mA) [12.4% low].  I obviously haven't corrected the position of the decimal.  Remember, the actual current through the meter is 2.5 mA is both cases.

About a 0.12 ohm resistor will correct the magnitude of the of the reading when the meter's switch is in the mA position.  But, I prefer having the decimal point in the correct position.  Being in the A/mA jack will remind me that mA is the actual display units.  I might purchase some 0.10 ohm resistors with less precision hoping to get one a bit low in value which will improve the mA reading's accuracy when the meter's switch is in the uA position.
 
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Online NivagSwerdna

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #219 on: July 18, 2017, 04:52:56 PM »
I'm quite tempted by this meter as my old MasTech doesn't have a uA range but now in two minds due to the lack of low mA ranges.... tricky!

... however I really do need something to measure in the 10uA type area MCU in standby for battery applications.... what to do!  |O
 

Online plazma

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #220 on: July 18, 2017, 04:55:52 PM »
I'm quite tempted by this meter as my old MasTech doesn't have a uA range but now in two minds due to the lack of low mA ranges.... tricky!

... however I really do need something to measure in the 10uA type area MCU in standby for battery applications.... what to do!  |O
Buy both AN8002 and AN8008 :)
 

Online alm

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #221 on: July 18, 2017, 04:57:42 PM »
Assuming your current meter has decent mV resolution, you can use an external shunt resistor between the power supply (battery) and micro. A 1 kOhm resistor would give 1 V/mA, or 1 mV/µA, resolution, and should have a low burden voltage at that current.
 

Online wilfred

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #222 on: July 18, 2017, 05:07:02 PM »
I'm quite tempted by this meter as my old MasTech doesn't have a uA range but now in two minds due to the lack of low mA ranges.... tricky!

... however I really do need something to measure in the 10uA type area MCU in standby for battery applications.... what to do!  |O

It's cheap enough to buy it just for the features you like about it. It was never going to be the perfect one single meter. If you have other meters that do other things like safely measuring high power then slot it in to your kit for the times having it will be useful.
 

Offline ebastler

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #223 on: July 18, 2017, 05:40:58 PM »
I'm quite tempted by this meter as my old MasTech doesn't have a uA range but now in two minds due to the lack of low mA ranges.... tricky!
... however I really do need something to measure in the 10uA type area MCU in standby for battery applications.... what to do!  |O

You are hereby officially granted the right to keep your old Mastech meter, and chose between that one and the AN8008 depending on your application.  :P

Having two meters (at least!  ;)) is good anyway, for those situations where you want to monitor two separate voltages, or voltange and current, or...
 

Online NivagSwerdna

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Re: AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
« Reply #224 on: July 18, 2017, 07:19:55 PM »
You are hereby officially granted the right to keep your old Mastech meter, and chose between that one and the AN8008 depending on your application.  :P
:-+
Thanks for the permission. it was enough to get me to click on ebay... £14.95 spent, it should be on the slow boat now.... probably arrive whilst I am away on hols.
 


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