Drawing Number: 21088
Revision: NR
OPERATION MANUAL FOR
ICP
INDUSTRIAL PRESSURE SENSOR
Series 121
Models 121A21, 121A22, 121A23, 121A24
Models 121A31, 121A32, 121A33, 121A34
3
Typical ICP
Connection
4.1
POLARITY
The 121 Series Pressure Sensors produce a positive-
going output voltage in response to pressure on the
diaphragm.
5.0
CALIBRATION
The discharge time constant of the Series 121 is too
short to allow calibration of the sensor by static
means. The 121 series can, however, be calibrated by
dynamic means using a pulse calibrator such as the
Model 903B02. By this method, the sensor is
subjected to a series of calibrated step changes in
which a linear graph can be plotted over the full range
of the unit.
PCB provides recalibration service on request. If
such service is needed or desired, consult the factory
for details.
Four sensors in the 121 Series (121A21, 121A22,
121A23, and 121A24) have discharge time constants
of sufficient duration (100 secs.) to use dead weight
testers for calibration.
Following is a brief laboratory procedure for
calibrating a pressure sensor using dead weights.
5.1
STATIC CALIBRATION PROCEDURE
FOR TIME CONSTANTS OF MORE THAN 100
BUT LESS THAN 500 SECONDS
1. Place sensor on test fixture with coaxial cable
connected to oscilloscope.
2. Apply known pressure to sensor diaphragm
(within range of instrument) using dead weight.
3. Remove weight and read change in output voltage
(mV) corresponding to input pressure (psi).
4. Repeat Steps 2 through 4 in 20% increments
within range of sensor.
5. Plot readings on x-y graph (voltage on the y-axis
verses pressure on the x-axis).
6. The slope of the line and the sensor sensitivity is
mV/psi.
6.0
PRECAUTIONS
1. To avoid destroying the built-in amplifier, do not
apply a voltage to the sensor without a current
limiting device (20 mA maximum) in the line such
as those incorporated in all PCB units.
2. Do not subject sensor to temperatures exceeding
250°F (121°C).
3. Do not exceed maximum pressure rating.
®ICP is a registered trademark of PCB Group
