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Stuart_Wales

Resistance Testing

3 posts in this topic

What's the best method to retro fit a test that will detect the presence of a 31 to 35 ohm (range) resistor and then fail a 0.4ohm variant at 13.4v D/C.

Thanks.

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Don't know if I really understand what you are looking for here.

What are you planning to use, a PLC, microcontroller or some passive components ?

A very easy way to detect that low resistance (with a PLC) is to connect a 500 ohm resistor to the 13,4V supply, and the other end of the 500 ohm resistor will be your positive test point, the negative test point is then ground.

With 30 ohm connected to the test point, you will have 0,758 V at the test point.

With 35 ohm, 0,876 V.

0,4 ohm is roughly zero Volt, and no (test) resistor connected is 13,4 Volt.

Easy to detect with an analog input.

You could also a PT100 input, 30 to 35 ohm would give you a reading of roughly -160 to -170°C.

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