• High Stability
    • Lower in cost than infrared, GC or MASS specification
    • Fast Response
    • Digital Readout
    • Long life thermal conductivity cell
    • Alarm contacts and low flow alarm optionally available
    • Built-in sample pump
    • Available in wall mount, rack mount, panel mount,
    • portable and explosion proof models
    • Sampling system available for most application
    • Optional automatic calibration
    • Cabinet purge system available for hazardous areas


TypeField / wall mounted
Detectable gases / parametersH2, O2, CO2 ( Binary gaseous mixture )
Electronics / processorMicro-controller
Power supply110 /220 VAC 50Hz
DisplayGraphic LCD
AlarmControlled alarms
Output4 – 20 mA Standard, individual relay, potential free contacts to
control alarm
Digital OutputRS 232 / 485
TechnologySensor Specific
Resolution1 mg/m3, 1 PPM, 1% V/V, application defined
Accuracy± 2 % FS
Response timeless than 30 sec, sensor dependent
Operating temperature0 – 55 °C
Flowrate0.5 to 0.9 L/min
EnclosuresWall mounted NEMA 12 (122N 12), NEMA 4 (122N 4), Panel
Mount (122 PM), Explosion Proof (122 Ex), Rack Mount (122RM)


The Model GA – 251 Thermal Conductivity (TC) Analyzer has many applications in industry where the measurement of one gas in a two gas or some multi-gas mixtures is required. The HNL Thermal Conductivity cell is temperature controlled and its high stability enables it to be used even in high purity measurements. Since the Thermal Conductivity cell does not consume the sample or have any moving parts, hot wires or sealed chemicals, it will last for many years. In operation : The Thermal Conductivity cell detects the rate at which the sample gas conducts heat away from a heated thermistor with reference to a similar thermistor surrounded by air. A sample containing the gas to be measured will cause the temperature, and its resistance, to change with respect to the reference thermistor. This will cause an output from the wheatstone bridge measuring circuit which is calibrated and displayed on a digital meter. Recorder outputs and alarm are also available.

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