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Important note regarding version OLC 20 High Temperature Detector
§ The OLC20 HT sensor is powered by a DC supply from the ISC/OLDHAM measuring
device. This current depends on the sensor operating temperature. The higher the
temperature, the lower the supply voltage. The device current rating is factory-set to suit the
operating temperature.
§ The sensor is zeroed on the device when the sensor is at its stabilised operating temperature.
If the operating temperature falls or rises as a result of the process, the zero signal will vary
accordingly. For example, a 100°C variation causes a sensor zero drift of +- 15% LEL CH4.
§ Sensor sensitivity is factory-set. On site, sensor sensitivity can be calibrated on the device
when the sensor is at its stabilised operating temperature.
1.2. Replacing a cell unit on OLC 20 or OLC 20 D
When?
- - When the cell unit is damaged or cannot be calibrated.
- - On a preventive basis.
How? See the following page
- Switch off the relevant measuring channel.
- Remove the cell unit to be replaced.
- Replace it with a new unit.
- Switch the channel back on and check that it operates correctly.
2. Transmitters OLCT20/20D and OLCT40/40D
These types of transmitters are equipped with a precalibrated cell unit and do not require any
adjustment on installation.
However, as they constitute safety equipment, it is recommended that these types of
TRANSMITTERS should be calibrated at least twice a year (in normal operating conditions).
2.1 CALIBRATION
These types of transmitters equipped with a precalibrated cell unit are designed to allow quick
servicing action on site.
- After removing the cell block from the transmitter, calibration is performed using a
calibrating bench provided for that purpose.
Note:
To operate this bench, see the operating procedure supplied with it.
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