Drawing Number: 40955
Revision: NR
ECO#: 39372
OPERATION MANUAL FOR
FREE FIELD BLAST PRESSURE PROBE
Models 137B21X, B22X, B23X, B24X
1
1.0
INTRODUCTION
The Series 137B2XX Free Field Blast ICP
®
Pressure
Probe is designed for measuring free field blast and
shock tunnel pressure time profiles.
Designed with an ICP
®
built-in source follower
amplifier, the 137B2XX Series offers sensitivities of
1, 20, 10 and 100 mV/psi with full-scale ranges from
0 to 50, 250, 500 or 5000 psi. The 137B2XX Series
is constructed with a stable quartz piezoelectric
element in an Invar housing
2.0
INSTALLATION
In field blast measurements, mount the Series
137B2XX pressure probe in an axial direction to the
blast source. The probes should be elevated high
enough off of the ground such that ground does not
interfere with the measured pressure. See photo 1.
Photo 1
The sensing surface should be aligned in a vertical
plane with respect to the ground as shown in photo 2.
Avoiding direct exposure of the diaphragm to
sunlight is good practice so that changing
temperatures throughout a test day do not change the
sensitivity of the sensor. In any case care must be
taken such that the sensor’s diaphragm is not oriented
down to avoid ground reflections.
In some cases, where flash temperatures such as those
generated by blasts and shock fronts are present, it
may be necessary to thermally insulate the diaphragm
to minimize signals generated by these effects.
Photo 2
Common black vinyl electrical tape has been found to
be an effective thermal insulating material in many
cases. One layer may be used across the end of
diaphragm and adaptor. See photo 3.
Photo 3
A silicone rubber coating approximately 0.010 inch
(0.25 mm) thick has also been proven effective in
many applications. General Electric RTV type 106 is
recommended (PCB Model 065A67). Apply the
rubber coating to the surface of the diaphragm and
allow it to cure in accordance with the manufacturer’s
instructions.
3.0
OPERATION
Using suitable cable, connect the sensor to one of
PCB's Series 480, 481, 482, 483, or 484 signal
conditioners or equivalent power supply. If using a
PCB line power unit, the equipment will supply the
137B2XX with an adjustable 2 to 20 mA constant
current at +22 to +30 VDC through a current-
regulating circuit. If using a battery-operated unit,
the constant current is 2 mA. See Guide G-0001 for
powering and signal utilization information pertinent
to all ICP
®
instrumentation.
