percussion ribbon controller AGAIN!!!!

Andy Main mainas at
Mon Nov 15 20:25:29 CET 1999

> You can deal with low resistance by using a bridge connection and a
differential (instrumentation) amplifier. Strain Gauge and RTD people do
this all the time... but it is a lot of circuit....

A couple of months ago I was working on a problem that involved measuring
very low impedances, namely electrical conectors between the card and
backplane of a telecoms rack system (typically 1mOhm).  I found a nice easy
and inexpensive way of doing this.  I passed a amp through the connectors
from a constant current source and measure the voltage across it using a
differential amplifier circuit using a gain of 100 and an OP177 (nice low
offset) as the opamp (with a 10k resistor as the load).  This worked
perfectly without the need for instrumentation amps or extra buffers, strain
gauges etc.

Anyway, that might be helpful!!!!


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