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## [Amps] meter internal R value, quick and easy.

 To: [Amps] meter internal R value, quick and easy. nospam4me@juno.com (skipp isaham) Wed, 31 Jul 2002 23:31:09 -0700
 ```I was surprised to see that no one came up with the classic simple answer regarding the meter internal R post... - - Two Potentiometers, a 9 volt battery and one or two resistors will do the trick. - Assume the movement to be 50 uA unless otherwise known "in stone" that it is another value. I have surplus meters with full scale 1mA indicated, but having micro amp movements. - One must construct a simple current loop using a few simple parts. - Limit the max current to a "safe value" that will not peg (slam) the movement hard (might actually bend the meter needle). Pick a value like 47K min as your soft limit value, placed in series with a 250K linear pot and the meter movement. Observe polarities... - Adjust the series linear pot for full scale deflection of the meter. Leave the meter reading full scale and apply a second pot as described just below. - Place the second pot in parallel with the meter and adjust it for half scale on the meter. A 250 ohm pot is probably a good value to use. - With the 250 ohm pot set at some position which drops the meter reading from full, to half scale.... the meter and the 250 ohm pot share equal current. Thus.... their values are equal. Measure the value across the pot and you have your meter movement resistance. - In step one, you might decrease the value of the 47K resistor to obtain full scale meter readings on higher current meter movements. - A 1 milli amp "mA" movement might use a 4700 ohm resistor as your testing safe limit value. - cheers skipp - >Anyone know of a procedure where I can determine the internal resistance >without damaging the meter movement? or, am i SOL? Some are uA meters, >some volts and some watts -- so who knows what the intended range was. >Thanks, >Gerry, W1VE ________________________________________________________________ GET INTERNET ACCESS FROM JUNO! Juno offers FREE or PREMIUM Internet access for less! Join Juno today! For your FREE software, visit: http://dl.www.juno.com/get/web/. ```
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