EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: jase_31 on September 12, 2020, 03:13:14 pm
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Has anyone been able to check the accuracy of the Aneng A8008 (Or AN870) on low resistances. The meter as resolution down to 0.01Ohm How does the displayed result compare to a reference value? Is it consistent?
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I have an 8008. For two-wire sub-Ohm measurements, the meter really needs a 'Relative' mode to cancel out the resistance of the test leads. The A8008 doesn't have that. Nor does the 870.
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I thought the AN870 did have a relative mode.
The 8008 would include cable resistance, so you would have to subtract this manually.
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Has anyone been able to check the accuracy of the Aneng A8008 (Or AN870) on low resistances. The meter as resolution down to 0.01mA. How does the displayed result compare to a reference value? Is it consistent?
I'm not sure you can measure resistance using mA.
It might be at 10 Ohms but I wouldn't trust it much as you go towards 1 Ohm or less. At that point you need to worry about things like the temperature of the probe wires (and how you're handling them with your hot hands).
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I've been a big fan of the Aneng 8008. Over time I've come to rely on it for various measurements including voltage and current but I've wondered about it for resistance; not sure why this should be but it's been a lingering doubt.
When I read this thread I thought I'd do some more recent measurements before posting and sure enough resistance seemed to be way out. I tried reading a 1 ohm resistor that I had measured on a DE-5000 and a 34465A also with 4 wires. I couldn't even account for the lead resistance on the 8008.
There was no low battery indication on the 8008 (I think it has one in the lower left corner of the display) but I decided to check the batteries and found they were 1.490 and 1.491. I put some new batteries in the 8008 and what'ya know? Reasonable resistance measurements.
So I made several measurements and tried to account for the lead resistance on the 8008. It doesn't have a rel function but you can simply measure the leads with another meter (if you have confidence in the other meter) and do the math, or you can try just measuring the leads on the 8008 with the leads hooked together. Either way, you need to account for the leads if you are going to try to get accuracy below 1 ohm.
I didn't do a bunch of tests with the new batteries but I'd say, ballpark and horsemath, the 8008 at around one ohm with it's tenths and hundredths digits display will show you a reading that is perhaps within 0.5 ohm (and possibly better) of what you might get pretty quickly with the DE-5000 and what you might get as an average over 30 minutes with the 34465A.
I've found that when you get to less than 1 ohm you are definitely going to have to account for various things in including the leads (of course), settling (could easily take 10-30 seconds and maybe longer - settling seems to be a variable variable), and temperature, and probably other considerations.
Overall, my new and limited experience below 1 ohm is that to get measurements that are consistent and accurate below 1 ohm will require some time, patience, and head scratching. I don't see how you could even begin to triangulate it with less than 2 meters and probably 3, and probably at least two of those would have to support 4 wire Kelvin leads - and even then you might start to wonder about variances between the Kelvin leads.
At one ohm you are on the edge of a rabbit hole, by milliohms you are likely in it.
So is the Aneng 8008 going to be good to milliohms, pretty doubtful (especially since it only has two digits beyond the decimal point). Can it be useful down to 1 ohm, I think so.
As far as the Aneng 8008 goes in general, it offers very good value.
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It's terrible for use below 1 ohm. Test current I measure at 0.393mA and at 1 ohm it is measuring only 393uV or 2.5ohms/mV.
I find the rotary switch resistance is high and readings wanders due to oxididation. There is no null/rel function, so always doing math in my head for the actual resistance.
You're be better off to use an AN8008 on DCV and use your own current-source for measuring low ohms, but still missing a zero/rel/null function.
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With my multitude of 800x meters, I often found the selector switch to be wonky in low resistance mode. "Wiping" it usually helps, but I'ld never test anything I've got to rely on that way. In this case, four wire is the way to go and a good job for the bench or RLC meter.
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With my multitude of 800x meters, I often found the selector switch to be wonky in low resistance mode. "Wiping" it usually helps, but I'ld never test anything I've got to rely on that way. In this case, four wire is the way to go and a good job for the bench or RLC meter.
I noticed the wiping effect too.