Drawing Number: 21210
Revision: NR
AN IMPROVED TECHNIQUE FOR
UTILIZATION OF CONFORMAL BALLISTICS
SENSOR CALIBRATION DATA
5
Dial Gain Standardization
Many charge amplifiers feature a calibrated gain pot for
dialing in sensor sensitivity for the purpose of setting
system sensitivity to standardized unit of output voltage
(PCB Model 462A).
To utilize such amplifiers, dial in the actual value of
slope as determined by the calibration graph for the
particular ammunition lot.
Using the slope value effectively displaces the
calibration curve to pass through the origin (0) of the
calibration graph.
See Figure 5.
Figure 5
The indicated peak pressure P2 from the conformal,
which through scale factoring can be read to read
directly in psi (on a digital peak meter for example) is
simply added to the offset pressure to arrive at true peak
pressure, P1 + P2
This process can be further refined to, include a variable
voltage source as a bias in series with the output of the
charge amplifier. This voltage bias can be set to
simulate the offset pressure, and then the true peak
pressure can be read directly. (See figure 6 on the next
page)
Example:
Assume a 20 round calibration lot and attendant graph
yield a slope of .250 pC/psi and an offset of 5,000 psi.
Proceed as follows:
Dial the slope (.250) into the dial gain pot and select a
convenient full scale range over which to operate.
For example, for an expected full scale range of 40,000
psi, select 10,000 units/volt.
Now the indicated peak pressure can be read directly
from a digital peak holding meter such as the PCB
Model 451B.
If the offset supply is not used, simply add the offset
pressure (5,000 psi) to the indicated pressure to arrive at
true peak pressure.
If an offset supply is used as in figure 6 simply dial in
the offset voltage equivalent to offset pressure. Now the
offset will be automatically added and the true peak
pressure can be read directly from the peak meter.
