This measuring device reminds in the external sizes:
http://
www.fluke.com/fluke/caen/Bench-Instruments/Timer-Counters/6690.htm? PID=55086
Can hardly less.
Explain on an example as it works:
Before you two identical electronic schemes.
One of them faulty, and the second in a full order, for comparison (reference).
There is no need to connect these electronic schemes to power supply!
The measuring device a have two probs (on one for each scheme). When measure what or a point on the serviceable scheme, on the display of the measuring device (lcd) there is a curve which corresponds to an impedance in this point.
The second probe measure the same point only on the faulty scheme.
If two curves coincide (some deviations are admissible) that in this point malfunction isn't found .
If there are deviations between two graphic representations it is necessary to search for fail component (s) arround this point.
Thus it is possible to compare any points between electronic schemes and if will have the luck)), to find malfunction.