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So in my plans to build ppm for the rest of equipment I have for magnetic field measurments. I've decided to use Solenoid and Toroid sensors, also switching circuit will be made using KoehlerMag scheme. Now I'm thinking on Amplifier circuit: J.A Koehler uses 2-stage transistor amplifier(based on LM394)-good decision, but what about 2-stage OPAMP circuit(for example based on AD797)? Also it's interesting to hear about frequensy-signal measurement- I stoped on 2 methods: digital (base on Period measurement) and phase measurements.
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Crowbar,
You should get lower noise figures going with lm394 or fet discretes in the preamp, but circuit layout is critical with the Koehler / Bayot design
(have made some superb oscilators).
I have not got to the frequency determination part yet but Koehler makes a good case for the dsp phase mesurement approach, that is the way i will most likely go useing an et-arm stamp or similar. -
Yes- dsp offers high rate and precision, also I can work with them using LabVIEWComment
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