Anode and cathode circuit sides as viewed by inserted device - Page 1
Forum section: electronics / beginners

author: Back2Volts
author_rank: Unknown
timestamp: December 07, 2016, 12:15:32 am
content: I just got this tiny amp-meterhttp://www.ebay.com/itm/Mini-digital-ammeter-meters-Panel-0-1A-current-display-LED-blue-HP-/262675111808?hash=item3d28a81f80:g:NowAAOSwZJBYAZgyand got a bit confusedreading this piece of the extensive documentation:The white wire at the bottom is connected to the anode. the test device, the black cable to the cathodeAm I right thinking that the white goes to low side (-) of the line and black to the high side (+) of the circuit branch being measured ?

author: MaxSantos
author_rank: Newbie
timestamp: December 07, 2016, 12:49:10 am
content: The instructions are a mess, you are right about that... but if i had to guess (never used one before) i would say:- Smaller wires: power to the device (red=positive, black: negative)- Bigger wires: Since its current... connect either way. it should not be a problem. If the reading makes no sense (since it has no negative sign) revers it.Just a guess, never uses one of those

author: rs20
author_rank: Super Contributor
timestamp: December 07, 2016, 12:50:59 am
content: Just plug it in one way, then swap the wires if the output is the negative of what it should be? There comes a point where trying to read the instructions is actually the harder option.

author: xtoffer
author_rank: Contributor
timestamp: December 07, 2016, 06:13:46 pm
content: Quotecm!?Anyways looks like there's a shunt resistor on the board so I guess it's just to hook up the white and black pair in series. And as previously stated if it doesn't support negative flow, you might get a zero.

author: rstofer
author_rank: Super Contributor
timestamp: December 07, 2016, 07:52:39 pm
content: I would think the anode (white) would be the source and the cathode (black) the return. Electrically, that's kind of a mess because, in electric circuits, black would be hot and white would be neutral. Why not take a resistor and a diode, wire them in series and place them across the white and black in both orientations? I would size the resistor to get a low value like 10 mA. That way I could use a small wattage resistor. All I would be looking for is a reading.

author: Back2Volts
author_rank: Unknown
timestamp: December 07, 2016, 08:52:23 pm
content: QuoteIt is such a high resolution amp-meter that it can be called amp-centimeter!QuoteIt sure looks like the shunt has one leg on GND, so it can only be hooked on very low side. I started testing placing it on the high side of the load and was causing a short on the supply.As for reverse, it gives a zero reading.

author: sleemanj
author_rank: Super Contributor
timestamp: December 07, 2016, 09:49:22 pm
content: Small red and black are power for the meter, ideally it should be floating with respect to the measurement circuit.White is current IN to the meter, Large Black is current OUT from the meter.BOTH BLACKS ARE CONNECTED, this type of meter is not isolated, it is for LOW SIDE measurement unless your power supply to the meter is floating.If you use the same power supply for powering the meter, as for powering the circuit, at least in the ones I've used, the accuracy is terrible.

author: Back2Volts
author_rank: Unknown
timestamp: December 07, 2016, 10:12:43 pm
content: Are you aware of any of these cheap ones with isolation between power and shunt? Do they exist (cheap) ?

author: rs20
author_rank: Super Contributor
timestamp: December 08, 2016, 11:23:33 am
content: Quote from: Back2Volts on December 07, 2016, 10:12:43 pmJust make your own by sticking an isolated DC-to-DC converter module on the power input.