Drawing Number: 21114
Revision: NR
OPERATION MANUAL FOR
ICP
HIGH PRESSURE SENSOR
Series 108B
1
1.0
INTRODUCTION
The Model 108B is the ICP
(Integrated Circuit
Piezoelectric) version of the Model 118B11 Ballistics
Sensor. These models were developed primarily to
measure ballistics chamber pressures for R & D and
production testing of ammunition. Both models share
the same quartz pressure element.
The design features a one-piece diaphragm, machined
integral with the housing for ruggedness. The
diaphragms are coated with flame-sprayed ceramic to
minimize flash temperature effects.
The high-impedance voltage signal produced by the
quartz element in the Model 108B is impressed
across the input of a built-in microelectronic amplifier
(actually an impedance converter with unity voltage
gain) which converts the signal to a low-impedance
level voltage (< 100
) able to drive long lines and
be fed directly into readout instruments such as
oscilloscopes, peak meters, etc.
10-32 Co-Axial
Connector
ICP Amplifier
5/16 Hex
3/8-24 Thd.
Quartz Element
Ceramic Coating
Shrink Tubing
Sealing Tower
Quartz Plate
Figure 1: Model 108B Pressure Sensor
2.0
DESCRIPTION
The figure 1 above shows the internal construction of
the Model 108B.
The machined diaphragm is made from maraging
steel because of its high strength and toughness.
The 3/8-24 thread and flush diaphragm design are
conventional, providing direct interchangeability with
existing welded diaphragm-type piezoelectric sensors.
The simple, rigid piezo element (containing only
quartz, steel and ceramic) gives the 108B a very high
natural frequency and good linearity, even below 100
psi.
The microelectronic impedance converter is located
just below the connector and is fully potted to
withstand up to 100,000 g shocks. The signal at the
output of this amplifier is superimposed on a +11 V
bias level. This bias is removed in all PCB power
units. (See the PCB publication "Guide to ICP
Instrumentation" G0001B for a complete treatment of
the ICP
concept.)
3.0
INSTALLATION
The Model 108B Sensor mounts directly in existing
ports machined for PCB Models 118B01, 109B01
and 119A.
Unlike conventional diaphragm type sensors, the
108B is pressure sensitive over the entire frontal area.
For this reason, extra care should be exercised to
avoid bottoming in mounting hole when recessed
mounted and especially when mounting into existing
mounting ports.
A torque wrench should be used to monitor the
mounting torque value when installing the Series
108B. The recommended range is given on the
installation drawing.
3.1
MOUNTING
IN
EXISTING
RECESSED PORTS
Before installing the sensor in previously used
mounting ports, clean off residue from previous tests
as shown in figure 2.
This can be accomplished by hand reaming the 1/4"
diameter hole using a PCB Model 040A end cutting
reamer (or equivalent).
