The vibration signal fed into the P702B Transducer input connector passes through a low pass filter

(optional) and to the first gain stage which amplifies the signal by X1 or X10 according to the gain switch

setting. The signal is split and one path is routed to an integrating amplifier to become an output signal

proportional to velocity (mV/in/sec). It then rejoins the non-integrated signal at the ACCeleration/VELocity

selector switch. When the switch is in the ACCeleration position, the signal goes directly to the second

stage gain amplifier which can introduce an additional X1 or X10 gain. By using different combinations of

first and second stage gains, the output can be set for gains of X1. X10 or X100.

The fault monitoring circuit is built around a dual comparator which senses the DC voltage supplied to the

transducer’s internal amplifier. The comparator circuit is of the window type and when the transducer’s

bias output voltage exceeds the normal range, 6-16 VDC, depending on the transducer type, it illuminates

the FAULT indicator. Abnormal voltages which can be caused by extended signal overloads within the

transducer’s internal charge amplifier may trip the circuit. Normally, small transients will not cause the

fault indicator to light as it has a rather long time constant to prevent low frequency, high amplitude

signals from causing the indicator to illuminate erroneously.

The P702B can be supplied by the factory with an optional 6 dB per octave roll-off RC low-pass filter

incorporated into the amplifier.