What I take out of this is that it is probably best to view the Fluke 87-V as a 6,000 count multimeter as that is how it is calibrated. The 20,000 count mode is good for observing small drifts but the accuracy in that mode is not really calibrated as it can be less accurate as we have seen here. If I need a Fluke DMM with a higher count than 6,000 and/or a DMM with higher accuracy, I should be looking into getting the Fluke 289.
To be on the safe side, yes.
My experience with the hi-res mode in my relatively new Fluke 87V (less than 1 year old) is different from yours. Contrary to what’s written in the data sheet and to the word on the street, the hi-res mode does increase accuracy, bringing my F87V on par (i.e. within 1-2 counts in hi-res mode) with any better spec’d 60,000 count Brymen (I have two of those).
10 uA measured in 6000 count (top) and hi-res (bottom)
![](https://photos.smugmug.com/photos/i-kTwPMhM/0/87a35a37/M/i-kTwPMhM-M.jpg)
![](https://photos.smugmug.com/photos/i-6zkfqZp/0/dab579bd/M/i-6zkfqZp-M.jpg)
1 uA measured in 6000 count (top) and hi-res (bottom)
![](https://photos.smugmug.com/photos/i-58zSprk/0/f93619da/M/i-58zSprk-M.jpg)
![](https://photos.smugmug.com/photos/i-LbBhLND/0/5d401f7e/M/i-LbBhLND-M.jpg)
0.1 uA measured in 6000 count (top) and hi-res (bottom)
![](https://photos.smugmug.com/photos/i-wbvHmPK/0/8decce17/M/i-wbvHmPK-M.jpg)
![](https://photos.smugmug.com/photos/i-SZJkpHM/0/5a180e55/M/i-SZJkpHM-M.jpg)
I also happen to have an older F87V’s, bought about 7 years ago on eBay (with unknown history). In general, my both F87V agree with each other within a count (in 6000 count mode) and within less than 10 counts (in 20,000 count mode). The new one is always more accurate in hi-res mode (than in 6000 count mode), the old one is sometimes slightly less accurate in hi-res - but we are talking about 5-6 counts off (accuracy judged by comparing the readings against a 6½ digit Keithley).
At 0.1uA (and under), the old one behaves somehow like yours (much worse accuracy in hi-res):
0.1 uA measured in 6000 count (top) and hi-res (bottom). Old F87V on the left:
![](https://photos.smugmug.com/photos/i-NcmNdZ3/0/40a35027/M/i-NcmNdZ3-M.jpg)
![](https://photos.smugmug.com/photos/i-ZkkHKB2/0/c33f2208/M/i-ZkkHKB2-M.jpg)
At 1uA it's a tough call (6000 count top, hi-res bottom). Old F87V on the left:
![](https://photos.smugmug.com/photos/i-kSX9GPM/0/5dd42bb0/M/i-kSX9GPM-M.jpg)
![](https://photos.smugmug.com/photos/i-RLPj8d7/0/f4deae8e/M/i-RLPj8d7-M.jpg)
It might be that my newer 87V is optimized for better accuracy in hi-res mode, whereas the older one is optimized for better accuracy in 6000 count mode. But we are talking about differences of 1-2 counts in 6000 count mode, so all bets are off. Maybe the older one is just slightly off overall and this is only visible in hi-res mode (but it’s still within its published specs). Or maybe it's just random variance between meters not spec’d at such a high accuracy in the first place.
In relative mode, both F87Vs show higher accuracy in hi-res at the lower end of the scale (600.0uA). I was able to measure with both down to 0.05uA. Old F87V bottom left, new F87V bottom right, DMM6500 top:
![](https://photos.smugmug.com/photos/i-pfTq2cg/0/bd6522d9/M/i-pfTq2cg-M.jpg)
Having said that, the accuracy of most meters is generally reported at full scale and guaranteed over a reasonable range at the upper side of the scale (e.g. for measured values larger than 10% of a given scale). The lower you are on the scale, the higher the relative noise and the lower the precision of the measurement. You can’t simply measure 0.1uA on a scale of 600.0uA and expect the same precision you would get if you measured, say, 500uA on the same scale.
I wouldn't use an F87V to measure 0.1uA in the first place (not even an F289 or a Brymen 689S…). There are other meters for that.
About my tests: I don’t have a precision current source, so I used a Datel voltage reference in series with a 1MOhm resistor. All meters were in series. For the relative measurement, I disconnected the voltage reference, shorted the terminals and use the displayed values on each meter as offset.