what is wrong with my meter? - Page 1
Forum section: electronics / testgear

author: piggy82
author_rank: Newbie
timestamp: May 28, 2015, 05:57:06 pm
content: Hi, sorry for asking a newbie question. I recently purchased an Amprobe Am-270 from ebay and it tested vol/resistance pretty good. However, I noticed that it does not test current properly. Every time I turn the knob to A, mA or uA setting without lead touching anything, there is an initial reading about 7mA or 70mA and it gradually drops to 0mA in about 5 to 20 seconds. And if I use the meter to test current (like a simple battery+led test) there does not seem to be any meaningful reading at all other than the weird 7mA-->0mA drop, the LED does light up though.I tested the fuses and the resistance seems to be as low as ~1 Ohm, battery is new with 9.3V.Does this mean the meter is dead?...Thanks

author: electr_peter
author_rank: Unknown
timestamp: May 28, 2015, 06:11:31 pm
content: Hello,What you describe certainly sounds worrying, DMM should not behave this way in normal conditions.Before jumping to the conclusion, could you check few things:meter is set to DC amps or miliamps (not AC or AC+DC)only GND and current jacks are plugged inno VFD filtering is enabledno averaging is enabledno heavy electricity powered machinery or other low or high frequency noise sources are aroundDo you have(or can borrow) other DMM with current measurement capability? Connect these two meters in series, run simple test with resistor and battery.

author: piggy82
author_rank: Newbie
timestamp: May 28, 2015, 06:47:15 pm
content: Holy cow...Thanks a lot for your reminding and it turns out it to be set to AC current. I guess this is where I missed: on the manual it says:uA, mA, and A current FunctionsDefault at DC. Press SELECT button momentarily to select ACIt appears to me that the word "momentarily" suggests if I turn off the meter and turn it back on it should reset to the default.So I didn't pay attention to the AC/DC setting as I assumed it should be default to DC. Anyway it turns out if I select AC, it will stick to it even if I turn it off! And somehow it was set to AC current before probably by an accidental pressing the SELECT button. I should have paid more attention to the meter itself. Luckily I didn't fry anything.Thank you again for the prompt reply and suggestions

author: Muxr
author_rank: Super Contributor
timestamp: May 28, 2015, 07:01:31 pm
content: Actually I was going to suggest checking that you're set on DC current, but then I looked at your meter's picture and noticed DC was default in current mode. So not sure how you missed thatEven my 87V counts down on the last digit when in AC current mode with no leads connected. I think it's the feature of true RMS doing its magic when you first switch.

author: piggy82
author_rank: Newbie
timestamp: May 28, 2015, 07:03:39 pm
content: Quote from: Muxr on May 28, 2015, 07:01:31 pmIt was truly my carelessness:) Thanks.

author: retiredcaps
author_rank: Super Contributor
timestamp: May 28, 2015, 07:07:03 pm
content: Some Brymen meters, the Amprobe AM-270 is a Brymen rebadge, remember the last setting you used even when turned off.

author: electr_peter
author_rank: Unknown
timestamp: May 28, 2015, 07:14:05 pm
content: Quote from: piggy82 on May 28, 2015, 06:47:15 pmI am glad you found my reply useful.