Optical Scientific Inc
OFS 2000CW User’s Guide
P/N 1910-905
Rev. 03/28/13
34
3.13 TB2 Fault / Cal Relays & External Calibration
3.13.1 Fault Relay
Pins COM 1 and NC 1 are connected to a dry
contact relay The contacts close when the
system is powered up, and remain so during
normal operation. The contacts open for:
A and/or B voltage out of range
Temperature probe fault
Pressure probe fault
Heat Activator fault
Power failures
Relay contact are rated 30V/5A
– 250VAC/8A
3.13.2 Cal Relay
Pins COM 2 and NO 2 are connected to a dry contact relay. The contacts open when the system is
powered up, and remain so during normal operation. The contacts close when the system enters a
calibration check cycle, and open when the calibration check is finished.
3.13.3 External Calibration Input
Pins EARTH and EXT CAL IN are provided for the user to connect to a simple momentary switch to
initiate a calibration check cycle manually. The external calibration request is activated when these
pins are shorted for more than 0.1 seconds. They connect to the system microprocessor, and signal a
calibration check cycle when grounded.
NOTE:
If the 24-hour automatic calibration cycle is enabled when a calibration cycle is
initiated manually, the 24
–hour timer will be set to this new starting point. Check with
your control center or data recording/monitoring personnel to avoid any unexpected
data stream interruptions.
Figure 3.27 Terminal Block 2
DO NOT APPLY VOLTAGE TO THE
EXTERNAL CALIBRATION INPUT PINS
