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Introduction
The 421B3X-Series Differential Charge Amplifiers are designed to convert the high-impedance output
of a differential, charge-mode piezoelectric sensor to a low-impedance voltage output. These amplifiers
may be used with either quartz or ceramic, differential charge-mode piezoelectric sensors.
Description
The amplifier operates on a 22 to 28 VDC power supply. The amplifier employs a high gain amplifier to
perform the impedance transformation. The output of the amplifier may be in voltage (mV) or current
(μA) and may be scaled in terms of acceleration (g), pressure (psi or mbar) or velocity (in/s or mm/s).
The electronic circuitry of the amplifier is incorporated into a molded aluminum enclosure. The amplifier
has factory-configurable high-pass and low-pass filters. Furthermore, RFI filters protect the input and
output against radio-frequency interference and other electromagnetic influences.
The amplifier is available in three variations, as noted in the table below.
Model
Sensor Type
Input
Output
High Pass
Filter (-3dB)
Low Pass
Filter (-1dB)
421B30
Pressure
Sensor
17 pC/psi
350 mV/psi or
µA/psi
10 Hz
5 kHz
421B31
Accelerometer
10 pC/g
100 mV/g or
µA/g
10 Hz
1 kHz
421B3X
Pressure
Sensor or
Accelerometer
Configurable
Configurable
Configurable
Configurable
Installation
Mount the base of the amplifier to a flat surface near the sensor,
with the amplifier’s input as close to
the sensor as possible. The cable length between the sensor and the amplifier should be as short as
possible to reduce the introduction of triboelectric noise into the system.
The 421B3X-Series housing is connected to the common (
Ⱶ) terminals. Therefore, the amplifier must be
mounted so that the housing is isolated from ground.
