Is this normal behaviour? Victor 88B multimeter current measurement (solved!) - Page 1
Forum section: electronics / testgear

author: Fezder
author_rank: Regular Contributor
timestamp: March 02, 2019, 01:51:42 pm
content: Shame on me for still using such cheap multimeter, but I don't have any better... (looking for better one for my next birthday...)I noticed this behaviour, look where leads are connected, and what setting is on switch. I'm feeding 1A through 10A range, but I still get....something (10mA) at 200mA range selected.Image:

author: ModemHead
author_rank: Frequent Contributor
timestamp: March 02, 2019, 07:20:29 pm
content: Normal behavior. And no need to apologize for your equipment.As you probably know, the multimeter indicates current by sensing the voltage across a shunt resistor. Your 2000-count meter has a 200.0mV A/D converter at it's heart, with a resolution of 100uV. Pictured here is my best guess of your meter's current-measuring configuration:It's common for current shunts to be "stacked" like this. The "A" jack is dedicated to the high-current shunt. For lower currents, the range switch routes the "mA" jack to different shunts. The voltage sense is taken from the top of the stack. For higher current ranges, the unused shunts simply become part of the series input resistance to the A/D. Negligible due to the high impedance input of the A/D.A 1.00A current into the A jack will develop 10.0mV across the 0.01 ohm shunt. So the display will show "100". The switch position determines where the decimal point is shown.

author: Fezder
author_rank: Regular Contributor
timestamp: March 02, 2019, 07:44:33 pm
content: Huh, didn't think of such stacking shunt resistors. Thanks! This cleared things up!

author: retiredcaps
author_rank: Super Contributor
timestamp: March 03, 2019, 12:14:27 am
content: Modemhead provided an excellent explanation.I will only make a suggestion if you are looking for a new meter. I suggest one with a better user interface or UI.I find the Victor 88B has too many dial positions and the dot on the rotary switch to be too small. This all leads to potential operator error and "oops" moments when the UI rotary dial is set to the incorrect position because it is one turn away or 180 degrees from the desired function.Some white paint on the rotary dot would help.In addition, it looks like the LCD doesn't show the actual unit of measure whether it be resistance, voltage or current.

author: Fezder
author_rank: Regular Contributor
timestamp: March 03, 2019, 09:11:24 am
content: Yeah, indication sucks. We had "oops moment" with teacher when dial was supposed to be in 750V, we were measuring MAINS. Dial was in capacitance range. Obviously, this would have led to potential safety hazard. Well, one one my school buddies measured mains voltage with DC voltage. Thankfully it was noted before anything happened.These scenarios happened many years ago, and I got another one of these meters. Another has in fact small stripe of yellow tape, to indicate dial position. Also, even it says 200mA range is fused....well, it has fuse, only It is not proper one; those resettable ones.I had brymen 14s while ago, but It's connectors broke. I bought it from flea market for 20€, so wasn't big loss that it broke. Apart from fact it was much more rigid, safe, and overall better.For next meter, I've thinked long time for brymen, since those appear to be good value. Probably 869s,