# How connect ammeter from ebay [closed]

sorry for stupid question but I do need help with connect of my ammeter from ebay. I bought this Ammeter 0-50A but there is no connection diagram So I try:

1. connect Vcc and GND to 9V and display turn on with value 0.0
2. connect white to negative, after load and black to gnd of load supply - but load (device) not work, it look like there is no connection between white and black thick wire. I try measure resistance and there is 5kOhms

If you look on photos there is some cooper wire between two holes on bottom, on other photos there is R050 but I do not have wire or ressistor on ammeter.

Can somebody help me with connection ? Thanks

• Junk it and buy a unit with documentation. – Leon Heller Jan 23 '18 at 12:25
• Why would you buy something that you don't know how to use and that doesn't come with directions!? Or, at least ask before buying. This boggles the mind. – Olin Lathrop Jan 23 '18 at 12:46
• You want to put 50A through those wires. – Oldfart Jan 23 '18 at 12:59
• Ceterum Censeo: We should have a close reason for "asker bought undocumented stuff and doesn't ask seller, but us, for documentation". – Marcus Müller Jan 23 '18 at 13:02
• Asker bought undocumented stuff and doesn't ask seller, but us, for documentation. – Olin Lathrop Jan 23 '18 at 13:04

What this device must be doing is measuring voltage on this R050 (0.05 Ohm) resistor and converting it to the value of current. The device really misses the documentation, and as Leon said in comment to your question you either get documentation for it, or better junk it.

Red/Black wire pair seem to be the power supply for the board, power voltage is unknown, thus you can not be sure about its reliable operation unless you disassemble it, draw the circuit, and figure it out yourself, or read it in trusted documentation.

Thick Black/White pair seem to be the one to connect into the circuit to measure the current.

I wonder how much current the device can withstand as R050 resistor must be too weak and will just burn under high currents. Specification is scarce on it, and I guess Measuring Range: DC0-1A, DC0-5A, DC0-10A, DC0-50A, DC0-100A means different type of resistor/shunt soldered. Which one did you buy?

Finally, to be sure you understand basics - this device measures current, not voltage. It means that you can not just connect it to the poles of the power supply as it will cause enormous current and burnout of the shunt resistor. You must connect this current meter device in series with the load.

it look like there is no connection between white and black thick wire. I try measure resistance and there is 5kOhms

Sounds like shunt resistor is dead.

My advice: request documentation from the seller, including connection diagrams.

• I try get documentation but without success :( I bought 0-50A version – Fires_CZ Jan 23 '18 at 13:14
• Sorry I maybe explaint it wrong. my connestion is like normal multimeter positive -> load - > ammeter -> negative – Fires_CZ Jan 23 '18 at 13:14
• Good, so we and you know that it is not you fried the device as you seem have connected it properly :) – Anonymous Jan 23 '18 at 13:19

You can solder a 50 mOHM = 0.05ohm resistor like on the picture. The tube is the same as a resistor. However be careful and find a through-hole resistor for high Amperes.

The tube is a resistor of a kind.

Or go after a 50 mOHM = 0.05ohm SMD like in the example.

So you undertand that's a SHUNT resistor to measure the current.

I edited my mistake.

An example of a shunt resistor to buy and a small guide for Shunt resistor.

MOUSER SHUNT RESISTOR

Guide

• "R050" is 50 milliohms, not 50 ohms – brhans Jan 23 '18 at 12:29
• 50 Ohm resistor to measure 50 Amps? – Finbarr Jan 23 '18 at 12:29
• YOu are Wright. It's a 50MOHM shunt resistor. – Dimitri Jan 23 '18 at 12:30
• So write: 50 mOhms (0.05 ohms) not 50 MOHMS (50000000 Ohms) – Bimpelrekkie Jan 23 '18 at 12:44