Westach 720-4a sensor

Greetings,

Has anyone seen or developed a characterization of this tach sensor?
It is a combined magnet/coil combo used to generate a pulse when a
bit of iron speeds past(Ampere's law). In my case, I have 6 steel AN5
bolt heads/revolution roughly 3/32" from the sensor head at roughly 1000
inches/sec max.

I'd like to know the expected output voltage and impedance so I can
compute the input resistor for a 4n25. I need to divide the output
pulse rate by 4 with a little TTL to get it into the frequency range for
my tachometer system.

Any advice?



Ira N224XS flying, but due for a little panel rework

Ira,
The diode on the 2N25 will drop about 1.6V at about 10mA. I am not
smart enough to calculate output characteristics of your generator but
my intuitive feel is that you may not have enough output (especially
at cranking speeds) to drive the diode. If it was mine, I would
connect 100 Ohms in series with the 2N25 diode and try it. Use a
scope and you can see what the real-world signal is.
Regards,
Sid Knox


Ira Rampil wrote in message ...
Greetings,

Has anyone seen or developed a characterization of this tach sensor?
It is a combined magnet/coil combo used to generate a pulse when a
bit of iron speeds past(Ampere's law). In my case, I have 6 steel AN5
bolt heads/revolution roughly 3/32" from the sensor head at roughly 1000
inches/sec max.

I'd like to know the expected output voltage and impedance so I can
compute the input resistor for a 4n25. I need to divide the output
pulse rate by 4 with a little TTL to get it into the frequency range for
my tachometer system.

Any advice?



Ira N224XS flying, but due for a little panel rework