Wiring load tester - Page 1
Forum section: electronics / projects

author: Liteace
author_rank: Regular Contributor
timestamp: September 01, 2019, 11:00:12 am
content: Would this be poss, I would like to build, with the help of you guys a self powered load tester for testing long run underground wiring, I have access to both ends of the wire and also have a 12 volt power supply, the power supply is capable of producing 80 ish amps, Ive been testing the wiring with a vehicle headlamp bulb that draws about 4 amps and DMM.What I would like if poss is a small'ish project box with a volt and amp meter built, something likehttps://www.ebay.co.uk/itm/2x-AC-60-500V-0-100A-Digital-Voltmeter-Ammeter-Dual-LED-Amp-Volt-Meter-Shunt-New/383104653214?hash=item5932d1179e:m:msct256VIz2Ol0NUDaog_hgin and a pot so I can crank up the the amps, I I'd like aprox 0 to 4 ampsif it is poss, where would I startThanks

author: ledtester
author_rank: Super Contributor
timestamp: September 01, 2019, 11:50:26 am
content: What exactly do you want to measure? What gauge wire are you testing?If you just want to know the resistance of the wire, your DMM might be able to do that itself.The panel meter you linked to only measures AC voltage and current.

author: Liteace
author_rank: Regular Contributor
timestamp: September 01, 2019, 12:17:20 pm
content: I want to test the wiring condition, the power supply has a volts out meter, that get fed in one end then I test the wiring the other end with bulb and DMM, if the wiring is good I get a slight volt drop due to length of wire, if the wiring is bad due to breaks or corrosion then it gets chopped outWhat I want to do is build if poss a little load tester so I can get rid of DMM and bulbMaybe this meter is betterhttps://www.ebay.co.uk/itm/Digital-LED-100V-Voltmeter-10A-Ammeter-Panel-mount-volt-amp-meter/152885694791?hash=item2398b29147:m:m_oggB8PrmZeLzRSclZd-Wg

author: ledtester
author_rank: Super Contributor
timestamp: September 01, 2019, 12:51:20 pm
content: How about a 9V battery, a 1K resistor and an LED? If the wire completes the circuit you know it isn't broken.I don't see the point of running 4A through the wire just to see if it is broken or not. If you want to know its resistance just use a DMM - it uses much lower current and you can calculate what the voltage drop will be at higher currents. Running 4A through a wire not designed to handle it can lead to it melting and breaking which will be a real bummer for you if it is underground.

author: OM222O
author_rank: Frequent Contributor
timestamp: September 01, 2019, 02:08:40 pm
content: just tie the two ends of the wire together at one end, then measure the resistance at the other end using any cheap pocket DMM?the wires have a known good resistance. if the measured resistance is in the nominal range, then you know they're good. if the resistance is higher than expected, then you know there are breaks / corrosion. if it's a lot lower than expected, there are shorts somewhere.If you insist on applying a load AND measuring under load, then you should use one of those cheap panel meters which can measure current and voltage, but they might not be too accurate. it's possible to roll your own using an MCU and an ADC which can be more accurate. then you fit everything in a small package and call it done. Even if you want to test the circuit under load, it's way easier to short one end of the cable and work at the other, rather than applying a PSU to one end and testing at the other end. the results will be the same.