Products > Test Equipment

AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter

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Fungus:

--- Quote from: Mark Hennessy on July 15, 2017, 06:32:56 pm ---In mA, mine met the 1.5% spec. The worst error was at 5mA, where I got 4%, but of course, 1 count is 2% at 5mA. Factor in the "3 counts" part of the specification, and 5.2 is indeed OK for 5.0mA. Elsewhere, it was comfortably within 1%.

--- End quote ---
I'd be happy with that.


--- Quote from: Mark Hennessy on July 15, 2017, 06:32:56 pm ---Personally, I would have preferred it if they'd not bothered with the square wave output, and used the switch position for mA, with a different shunt.

--- End quote ---
Or move the lower ranges up by a factor of 10. How many people really need to measure nanoamps?


--- Quote from: Mark Hennessy on July 15, 2017, 06:41:09 pm ---As I mentioned earlier, the square wave comes from quite a high source impedance (about 2k). So by the time you've fed that into an 8 ohm loudspeaker, there's hardly any voltage there. I tried a very sensitive 15 ohm speaker, and you have to hold it to your ear to hear anything from it.

--- End quote ---

Something else I won't have to bother to check when mine finally arrives.  >:(

(I should have stopped reading this thread a few pages ago)


--- Quote from: deflicted on July 15, 2017, 06:56:36 pm ---Noob question: I seem to recall reading somewhere that square waves are bad for speakers because the flat parts look like DC, and DC ruins speakers.

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Only true if there's a lot of amps available. In this case there isn't, there's a 2k resistor between the battery and the speaker.

It can be a good idea to add a capacitor in series with the speaker to prevent long periods of DC from damaging the speaker (the capacitor will charge up after a short period of time and block the DC).



(image chosen randomly from google)

exe:

--- Quote from: Fungus on July 15, 2017, 11:00:17 am ---Edit1: Reading the small print, that meter needs a weird 12V battery.

--- End quote ---

I have a similar unit, it uses a 12V battery, same used in many car remotes. Wouldn't call this an issue, but battery costs like half of DMM. I replace it every two-three years or so. It's only 2000 counts, but this is good-enough for most my purposes.

kalel:

--- Quote from: exe on July 16, 2017, 09:21:03 am ---
--- Quote from: Fungus on July 15, 2017, 11:00:17 am ---Edit1: Reading the small print, that meter needs a weird 12V battery.

--- End quote ---

I have a similar unit, it uses a 12V battery, same used in many car remotes. Wouldn't call this an issue, but battery costs like half of DMM. I replace it every two-three years or so. It's only 2000 counts, but this is good-enough for most my purposes.

--- End quote ---

On eBay, the cheapest I could find is about $1 for 1 or $2 for 5 batteries (I guess shipping comes into play). That said, I guess it shouldn't be far too much more expensive locally, if you search around. So, even the cheapest is probably about 1/4 of the meter. But 9v batteries are not much cheaper (if not more expensive) and with these cheap meters, a battery is always a good part of the price of the meter. What can you do. Maybe you could modify it to work with a cheap 3.7v Lipo, but I'm not sure if that's a good idea or not.

Fungus:

--- Quote from: b_force on July 15, 2017, 08:22:58 pm ---It's just to bad for the current, which blows my mind because the voltage ranges are fine.

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It's always a good idea to own more than one meter anyway, so that:
a) You can take measurements that need two meters (eg. power)
b) You can see two values in a circuit simultaneously (can be useful, eg. with batteries so you can watch the battery voltage under load)
c) You can occasionally check meter readings against each other. If you see a weird reading, how do you know the problem isn't the meter? There's no substitute for a second opinion, even if you own a Fluke 87V (in fact I'd have more overall confidence in my readings if I owned two of these than if I owned a single Fluke)


--- Quote from: b_force on July 15, 2017, 08:22:58 pm ---I was just wondering, wouldn't be an idea to develop a small daughter board to provide the correct input protection and maybe some extra extra tweaks to get a better current range?

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Or ... if this is super-important to you then make sure your second/third meter has a suitable mA range. It's simply not worth building "daughter boards" when an AN8002 costs $15.

Mark Hennessy:

--- Quote from: ocw on July 16, 2017, 12:05:34 am ---
--- Quote ---I finally got inside of the meter since the AC current measurements don't seem very stable.
--- End quote ---

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%.

--- End quote ---

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 87VAN8008Error1.03mA0.0mA-3.00mA0.0mA-4.01mA2.0mA-50.1%5.06mA3.6mA-28.6%6.06mA4.8mA-20%7.07mA6.1mA-13.7%8.05mA7.3mA-9.3%10.08mA9.5mA-5.8%15.01mA14.6mA-2.7%20.11mA19.7mA-2%30.56mA30.2mA-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 :palm: 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.

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