I finally got inside of the meter since the AC current measurements don't seem very stable.
While the two digit ammeter for 1 - 10 mA DC readings might have limited value, it is of no use for AC readings in that range.
While I had reasonable accuracy on the AC uA readings from 10 to 1000 uA, things fell apart when I tried to read 1000 uA as 1 mA AC. The AN8008 showed zero mA for that measurement. My next test measurement was at 3.3 mA. The AN8008 generally stayed at a reading of zero with an occasional jump up only to soon return to zero.
My next step is at 10 mA. By then I had a steady reading which was 8% low. At 30 mA the meter became useful with a reading which was only 1% low. By 75 mA and above the meter's surprising accuracy returned with the accuracy typically below 0.2%.
Mine is better than yours here as well. I wonder if I'm lucky, you're unlucky, or this is just the sort of sample-to-sample variation we have to expect at this price point?
On uA AC, mine was spot-on when compared with a Fluke 87V. Really, no more than 2 or 3 counts away in both ranges, right down to the smallest signals. That impressed me, to be honest.
On mA AC, then yes, it's not brilliant at very small currents:
Fluke 87V | AN8008 | Error |
1.03mA | 0.0mA | - |
3.00mA | 0.0mA | - |
4.01mA | 2.0mA | -50.1% |
5.06mA | 3.6mA | -28.6% |
6.06mA | 4.8mA | -20% |
7.07mA | 6.1mA | -13.7% |
8.05mA | 7.3mA | -9.3% |
10.08mA | 9.5mA | -5.8% |
15.01mA | 14.6mA | -2.7% |
20.11mA | 19.7mA | -2% |
30.56mA | 30.2mA | -1.2% |
So mine comes into spec at 30mA, and seems to hold it pretty well above that. I didn't try very high currents as that would have meant plugging up an amplifier, etc...
I tested with a 100Hz sine wave from an old Wavetek 162 function generator. My readings were stable within a count at all points - I wonder if noise was an issue for you?
Instinctively, I would treat all AC readings with suspicion when so near to the bottom of the range, but for beginners who pick up this meter, it's good to highlight this. Obviously the AN8002 is the one to buy for measuring currents in this region - buy one of each
The fact they're different colours helps (well, me at least) when doing something involving multiple meters, which is why if I bought a second BM235, I'd get the "vanilla" version with the red holster...
Oh, earlier I mentioned 1.5% for the current spec. That's for the AN8002 - I'd picked up the wrong manual. Sorry
The AN8008 is a bit tighter, at 1%+3 (and 0.8%+3 on uA) on DC. However, I don't think that changes anything I said earlier. Meanwhile, on AC, it's 1.2%+3 on mA and A, and 1%+3 on uA.