Precision Control Systems 915 - Manual (Page 20)

Page 17 of 21
Calibration
Generally components of the power control system hold their calibration very well over a long
period of time. Usually verification of calibration is all that is necessary. We suggest
verification or calibration be performed on a yearly basis. Calibration should be performed by
qualified personnel as dangerous voltages are present.
Power Controller
Refer to the power controller manual for specific calibration instructions. Calibrate using step
1, 2 or 3 below (use whichever is used most often):
1. When LOCAL setpoint mode is selected, the local setpoint potentiometer is used as the
source for the input. Adjust the zero and span potentiometers on the power controller.
The SPAN potentiometer is adjusted for 90 percent or rated line voltage for 900 dial
divisions of the local setpoint pot. The ZERO potentiometer is adjusted for 0 volts output
when the local setpoint is set to 000 dial divisions.
2. Voltmeter Option or No Options: When REMOTE setpoint mode is selected, use a 0-5
VDC source for an input. Adjust the zero and span potentiometers on the power
controller. The SPAN potentiometer is adjusted for 90 percent of rated line voltage for
4.5 VDC input. The ZERO potentiometer is adjusted for 0 volts output when the local
setpoint is set to 000 dial divisions.
3. Temperature Controller option only: When AUTO setpoint mode is selected, the
temperature controller is used as a the source for the input. Adjust the zero and span
potentiometers on the power controller. The SPAN potentiometer is adjusted for 90
percent of rated line voltage for 90 percent output of the temperature controller. The
ZERO potentiometer is adjusted for 0 volts output when the temperature controller is set
to 0 percent.
Panel Voltmeter Calibration
The front panel load voltmeter is calibrated to match as closely as possible the true RMS
voltage measured at the load terminals.
1. Connect a true RMS DVM to load 1 and load 2.
2. Connect another DVM across pins 1(+) and 2(-) of the EXT 200 RMS voltage
transmitter.
3. Turn the HEATER switch to OFF. Measure the voltage of EXT 200 pins 1(+) and 2(-) to
be 0.0 VDC +/- 10 millivolts. Adjust the EXT 200 zero potentiometer if necessary.
4. Verify the panel voltmeter reads 0 volts. If necessary, carefully remove the front cover
of the meter and adjust the zero potentiometer for 000 +/- 1 reading.
5. Turn the Heater switch to ON. Adjust the LOCAL SETPOINT potentiometer for the
following load voltage based on the voltage your system is configured for:
480 VAC units: 450 VAC
240 VAC units: 225 VAC
120 VAC units: 110 VAC
6. Measure the voltage of EXT 200 pins 1(+) and 2(-) to be the following voltage +/- 10
millivolts: