Understanding this circuit

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Blue_Electronx

Joined Jun 10, 2019
102
Hi,

I don't seem to understand the circuit attached. The comparator U2 is acting like some kind of relaxation oscillator, right? It's weird that U2 is powered from GND and -12V. As far as I know this circuit is used to inject an AC signal to the test coil when PB1 is pressed. But how does it exactly work?
 

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ericgibbs

Joined Jan 29, 2010
9,850
hi BE,
Where did you find the circuit.?
A link to a web site or some explanation on how the circuit is used would be helpful.
E
 
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