Teledyne OT-2 - Oxygen transmitter system - Manual (Page 15)

2-7 Teledyne Analytical Instruments
Model OT-2 System Operational Theory 2
2.3 Electronics and Signal Processing
The OT-2 circuitry consists of three stages: an input stage, a
temperature compensation/gain stage and an output stage.
The input stage consists of a current to voltage converter
producing a voltage signal that is proportional to the oxygen
concentration as detected by the sensor.
The temperature compensation stage contains circuitry that
compensates for the temperature effects on the output current of
the O
2
cell. A thermistor mounted in the sensor assembly monitors
the sensor temperature.
The output stage provides a 1-5 volt signal into a load >10K
ohms corresponding to 0-100% of full scale of the selected range.
The transmitter circuitry operates with a power supply voltage
range of 9-16 VDC. It is recommended that the output cable be
no longer than 10 feet. A shielded cable should be used when-
ever possible to minimize electrical noise pickup.
2.4 Oxygen Cell Block Heater
The OT-2 system is equipped with an insulated and electrically
heated cell block. The heater is switched on when the enclosure
temperature dips below 1
o C. The 3 watt heater is controlled by the
electronic control unit.
Note: The cell block insulation must be in place for the
heater system to be effective.
2.5 EMI/RFI Protection
The OT-2 System is well shielded from EMI/RFI. The transmitter
electronics are mounted within a grounded metallic enclosure,
and the electronics is housed within the main system enclosure. For
optimal transmitter performance, the main system enclosure
should be well grounded.