### Author Topic: Ammeter tester  (Read 341 times)

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#### darinsquared

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##### Ammeter tester
« on: March 27, 2020, 12:57:25 am »
I have a tractor with electrical problems. I performed a voltage drop test and found a 0.6V drop on the positive side (the negative side had insignificant voltage drop).  I want to build a ammeter to diagnose the problem. Here is my plan. I connect a shunt between the negative battery post and negative. Then connect an ammeter to the shunt to determine the current draw with all power usage turned off.  I pull all fuses individually until I find the fuse that causes the ammeter to go to zero.  Will this work?

#### Vovk_Z

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##### Re: Ammeter tester
« Reply #1 on: March 27, 2020, 08:10:18 am »
Sorry, I dont fully understand your plan. If there is something wrong, usually voltmeter and ohmmeter can help.

Maybe, it will be easier with multimeter like Unit UT210E - DC current clamp? They are about $50-$60. I've bought them for testing if there is some current leakage in my car.
« Last Edit: March 27, 2020, 08:15:22 am by Vovk_Z »

#### Gregg

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##### Re: Ammeter tester
« Reply #2 on: March 27, 2020, 07:35:40 pm »
Voltage drop from where to where and under what circumstance?
Does the battery discharge when the tractor is turned off and you are trying to find the parasitic drain on the battery?
Or when the tractor is running, there is a voltage drop from the positive battery terminal to some other connection point?
That being stated for your consideration; a volt meter measuring a voltage drop from one point of a conductor to another is a de facto ammeter, uncalibrated, of course. But the volt meter will show relative amperage under varying conditions.  The higher amperage, the higher the voltage drop across the two points.

#### bob91343

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##### Re: Ammeter tester
« Reply #3 on: March 27, 2020, 08:02:10 pm »
Yes it will work.  But easier might be to pull each fuse and measure across the terminals.  You will see voltage if there is a load; otherwise nothing.  Somebody sells a device to install in place of a fuse to measure current.

These automotive problems are often elusive, as the design is usually a mess of interconnected cables and connectors.

Smf