Electronics > Beginners
"Normalize" a variable amplitude sine wave
dannydnl:
Hello everyone,
So, i want to take the sinusoidal signal from a crankshaft sensor, that outputs a "variable" amplitude, then "normalize" it to about 3V peak to peak and offset it, so it doesn't go negative.
At low RPM the signal is about 1V pk-pk , and at max RPM it goes a little over 20V pk-pk.
Can someone point me in the right direction on how to proceed with this, and what type of circuit do i need?
To be honest, i don't know what to search for, cause "normalize a sine wave, circuit" doesn't yield anything good.
Thanks for any input.
retrolefty:
Lots of speed sensors were used on large compressors and other machines where I worked (large oil refinery) used passive and active sensors, typically variable reluctance pick-ups that wired to zero crossing differential op-amp comparator input circuits, effectively transforming sine wave to digital (voltage limited) square wave.
nfmax:
This looks like an inductive pickup, so the output voltage is proportional to the rate of change of magnetic flux, which is proportional to speed. So if you use an OPAMP integrator, you will get a sine wave of constant level regardless of speed. You can set the output amplitude by setting the time constant of the integrator. You will need a feedback resistor in parallel with the integrating capacitor, to stop the integrator saturating when the engine stops. The time constant Rf*Cf should be about 50s time the integrator time constant Rin*Cf.
You can then offset the output by applying a fixed current to the inverting input of the integrator OPAMP. The value of Rf, together with the input current, sets the output bias voltage.
Tomorokoshi:
Try something like this:
https://www.digikey.com/product-detail/en/texas-instruments/LM1815N-NOPB/LM1815N-NOPB-ND/228997
jesuscf:
--- Quote from: dannydnl on February 21, 2020, 05:07:04 pm ---Can someone point me in the right direction on how to proceed with this, and what type of circuit do i need?
--- End quote ---
"Logarithm amplifier" + "DC restorer"? What are you trying to measure? If you are interested just in the frequency of the signal, there are very simple circuits you can use.
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