Fluke 87v not measuring current - Page 1
Forum section: electronics / testgear

author: TurboT8er
author_rank: Newbie
timestamp: November 21, 2013, 03:18:13 am
content: I have a Fluke 87v with a blown fuse in the low current position (440mA). However, the high current setting should still read milliamps as a decimal. I tried to measure the current draw of a stompbox I built recently by connecting the leads in series with the battery. Made sure the leads were in the right holes on the multimeter, and made sure it was set to DC current. Nothing. It read 0.00.Just to make sure the current side was even working, I put the leads across a 9V battery, and it read 2-3 amps initially, then slowly dropped. Any ideas?

author: ConKbot
author_rank: Super Contributor
timestamp: November 21, 2013, 04:05:52 am
content: Have you tried it in high-res mode? (I think high res mode works for current too, not 100% sure) How much current draw are you expecting? if its under 10mA then it could be below what the meter can measure with the 10A shunt.

author: samgab
author_rank: Frequent Contributor
timestamp: November 21, 2013, 04:06:35 am
content: You proved with your test that the ammeter function is working. What range did you have it set to? Did you try changing ranges? What sort of current reading are you expecting? Can you make a video to show what's happening?

author: TurboT8er
author_rank: Newbie
timestamp: November 21, 2013, 04:09:18 am
content: Quote from: ConKbot on November 21, 2013, 04:05:52 amYep, same results. Should be around 300mA.

author: TurboT8er
author_rank: Newbie
timestamp: November 21, 2013, 04:13:10 am
content: Quote from: samgab on November 21, 2013, 04:06:35 amThere's not really a range dial. There's a setting for A/mA (high current) and one for mA/uA (low current). Probably not going to post a video. I'm sure I can get this figured out without going that far.

author: samgab
author_rank: Frequent Contributor
timestamp: November 21, 2013, 05:23:52 am
content: Quote from: TurboT8er on November 21, 2013, 04:13:10 amNot a range dial. Range button. On the mA/A range, you can select 6 or 10A ranges. On the 6A range you get A to 3 decimal places.On the 10A range you only get 2 decimal places. Since you don't know about the range button, you'll just be on auto range.As you know about the prove-test-prove method, and you've proven than the DMM A range is working, with the battery, then test your DUT, then prove again that the DMM is still working, and then you know that if you're not getting a reading from your DUT, that it's the Device that is at fault, not the meter.

author: TurboT8er
author_rank: Newbie
timestamp: November 21, 2013, 05:55:40 am
content: Okay, tried it again. This time, I had all the pots on the DUT turned up all the way, and had it hooked up to my amp while I tested it. It showed 0.019A, which is about half the expected rating. Normal operation still shows ~0.001A. And considering this is a clone of a circuit known to have 300mA, it shouldn't be that different.

author: TMM
author_rank: Frequent Contributor
timestamp: November 21, 2013, 09:17:04 am
content: Quote from: TurboT8er on November 21, 2013, 05:55:40 amWithout knowing which device is at fault you're on a wild goose chase. If you expect the circuit to draw 300mA then put a 33ohm resistor in series with a 9V battery and hook that up to the 87. Should show 200-300mA.

author: Unknown
author_rank: Unknown
timestamp: November 21, 2013, 10:23:08 am
content: I agree with TMM that currently you have no way of knowing if the meter or the DUT is at fault. I would take a low value resistor (for example a 1 ohm 1/4 W resistor), measure its resistance, then put it in series with the circuit and measure the voltage across it. Ohms law will then tell you the current.