22 Calibration
Signal Input Adjust
The SIGNAL INPUT ADJ potentiometer is used to set the
maximum Test Point voltage to approximately 5 VDC, as
measured between terminals TP and COM. The importance of
this step is to scale the input signal voltage to keep it well within
the range of the PCM4’s comparator chip. This calibration is only
approximate. A tolerance of 0.2 Volts is acceptable.
The SIGNAL INPUT ADJ is calibrated only when the PCM4 is
following a voltage signal. When the PCM4 is following a current
signal set the SIGNAL INPUT ADJ fully CW. See Figure 12 for
approximate calibration of SIGNAL INPUT ADJ.
To calibrate the SIGNAL INPUT ADJ:
1. Apply the true maximum voltage input.
2. Check voltage at TP vs. COM to verify that it is approximately
5V. Adjust SIGNAL INPUT ADJ if needed.
Figure 12. SIGNAL INPUT ADJ - Calibration Positions
0 - 5 VDC 0 - 10 VDC 0 - 25 VDC 0 - 250 VDC
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