BALLISTICS PRESSURE TRANSDUCER MODELS 165B02 AND 118A07 OPERATION MANUAL
4
NOTE: Do not attempt to use a charge amplifier that has
less than a 5 000 second time constant when in the long
position.
Several charge amplifiers are specially designed for use
with ceramic accelerometers for higher frequency
measurements. In general, these types are unsuitable for
calibration of quartz pressure transducers by quasi-static
means.
A factory charge calibration is supplied with each
transducer. Factory recalibration is available.
5.0
OPERATION
Most test setups include the Model 165B02 & 118A07
operating into an electrostatic charge amplifier, such as
the PCB Model 443B02. See Figure 5.1.
NOTE: Keep the input cable to the charge amplifier as
short as is practical. Electrical noise at the output of any
charge amplifier is directly related to input cable length
(capacitance).
Press the ground button of the charge amplifier and
adjust electrical zero if necessary. Range the amplifier
to give the necessary full-scale voltage. For normal,
drift-free operation, switch the charge amplifier time
constant selector to MEDIUM or SHORT during use.
5.1
Polarity
Since most charge amplifiers are inverting amplifiers,
the Model 165B02 & 118A07 is designed to produce a
negative-going charge for increasing pressure at the
diaphragm.
6.0
MAINTENANCE
The only maintenance required on the Model 165B02 &
118A07 is the periodic cleaning of the connector to
restore insulation resistance.
During use in damp environments or after a period of
storage, the insulation resistance of the transducer may
degrade (10
12
ohms is normal). To restore insulation
resistance, an ultrasonic cleaning in 99% pure isopropyl
alcohol is required. Then bake the transducer in a 250 °F
(121 °C) oven for several hours. If available, a vacuum
oven expedites the process. Allow the sensor to cool to
ambient temperature before re-testing the insulation
resistance.
Drawing Number: 21109
Revision: NR
