Raspberry JAM To Sensor, Gain Question

JAM attenuation resistors R[a] and R[b] are based on signal input level.

If signal input is +/-10 volts relative to ground, (a 40 volt differential signal), R[a] is recommended as 33K and R[b] is 12K.

If input signal is below an absolute span of 3 volts R[a] and R[b] are shorted out.

My sensors are Dave Nelson’s FMES (Fluid Mass Electrolytic Seismometers). The sensor second amplifier stage provides a voltage gain of 40 to provide +/-10 volts relative to ground.

Can’t I reduce the sensor second stage gain so I reduce the signal to below an absolute span of 3 volts? This should allow me to short out R[a] and R[b].

How does a “signal +/-10 volts relative to ground” compare to “an absolute span of 3 volts”? What reduction in gain is required to go from the higher to lower level?



Hi Bob,

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