Thread: Wetting Current Measurement

Exactly we doing the same way as you mentioned. 1.  Connect 12.5V power supply, resistor and ammeter in series. 2.  Adjust  the resistor (1.785K) to achieve a current of 7 mA 3. Without adjusting any further, break the circuit and insert the set of contacts under test 4.  Measure the current in the new setup. But I feel we setting up (7mA) high end. Our spec is 1-7 mA. It...

( This sounds like a perverted specification that was originally for measuring optical inputs which are only current sensitive.  You would want them to trip between 1 and 7mA or call them dead.  Not mechanical switches. , )

You're trying to measure something that has no meaning.  If the 12.5V and the 1.78kΩ are both completely stable, I'd be worried about any contact that showed less than 7mA.  A contact that shows 6.96mA has a contact resistance of almost 16Ω and that would be totally unacceptable.  If you measured only 1mA, that would mean a contact resistance of...

( Keith: I thought it was much lower than 10V, more on the order of a few tenths of a volt\(no references\). How do 1.5, 3V, and 9V battery operatted devices work reliably? Do they typically use gold in those applications, especially with units manufactured in China at minimal cost? and also 3\) Mercury switches. \(Not very PC with ROHS\) Thanks -AK2DM , )

( Not my field, but contact wetting should only matter for items such as relays.  Slide contacts, like what are found on even the cheapest of products, provide a surprisingly high amount of self-cleaning friction. , )

Could I check whether I have understood the test you are doing, and that we're not losing something in the language barrier? As I understand it, your test procedure is: 1.  Connect 12.5V power supply, resistor and ammeter in series. 2.  Adjust either the voltage or the resistor (please tell us which) to achieve a current of 7 mA 3.  Without adjusting any further, break the circuit and...