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Measuring variation in inductance

I was wondering what precautions I should take for measuring a coil's
inductance. Following some capacitive sensing approaches my idea was
to use a MCU pin for pulling a pin connected to the coil L1 HIGH and
then measuring the voltage drop across a resistor R1 in series to the
coil.

WRITEPIN+-----------o----UUUU---o--------o---------R1--------| GND
\----|<|----/ \--READPIN

By measuring the time it takes for READPIN to reach HIGH it should be
possible to calculate L1 given a known R1 value..right?
My concern is about the coil's kickback: is the parallel diode
sufficient to protect the readpin from excessive voltages ?
 
J

Jasen Betts

Jan 1, 1970
0
I was wondering what precautions I should take for measuring a coil's
inductance. Following some capacitive sensing approaches my idea was
to use a MCU pin for pulling a pin connected to the coil L1 HIGH and
then measuring the voltage drop across a resistor R1 in series to the
coil.

WRITEPIN+-----------o----UUUU---o--------o---------R1--------| GND
\----|<|----/ \--READPIN

By measuring the time it takes for READPIN to reach HIGH it should be
possible to calculate L1 given a known R1 value..right?
My concern is about the coil's kickback: is the parallel diode
sufficient to protect the readpin from excessive voltages ?

you've got the coil's parallel capacitance to consider too.
and the threshold that the readpin responds at may be unpredictable,
 
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