Oldham OLCT 200, User Manual, Page: 37 / 80

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OLCT 200 User Manual | 37
SECTION 4 -
OPERATING
INSTRUCTIONS
4.1 Routine Sensor Calibrations
Calibration is the most important function for insuring correct operation of the OLCT
200. The CAL MODE (flow chart shown in Figure 4-2) is designed to make calibration
quick, easy and error free. A successful ZERO and SPAN calibration requires only
four keystrokes. The 4-20mA output indicates CAL MODE by transmitting 3mA for 2-
wire installations and 1.5mA for 3-wire installations.
The OLCT wireless model’s 10-bit
output transmit 200-1000 counts for 0-100% full scale. It indicated cal mode by
transmitting 75 counts (-15.6% FS) to receivers on the network. After the calibration is
complete, 2/3 wire models transmit 4mA during the subsequent CAL PURGE delay to
prevent external alarms during calibration. Wireless models transmit 200 counts (884
counts for oxygen) during CAL PURGE. Local OLCT 200 alarm relays (if equipped)
are inhibited during CAL MODE. CAL MODE automatically exits if no keystrokes are
detected after 5 minutes.
Follow these OLCT 200 calibration guidelines:

Calibration accuracy is only as good as the calibration gas accuracy. Oldham
recommends calibration gases with NIST (National Institute of Standards and
Technology) traceable accuracy to increase the validity of the calibration.

Do not use a gas cylinder beyond its expiration date.

Calibrate a new sensor before use.

Allow the sensor to stabilize before starting calibration (approximately 5
minutes).

Calibrate on a regular schedule. (Oldham recommends once every 3 months,
depending on use and sensor exposure to poisons and contaminants.)

Calibrate only in a clean atmosphere, which is free of background gas.