Category: Baker Hughes

Theory of operation

Two ultrastable, precision glass-coated thermistors are used—

one in contact with the sample gas and the other in contact

with the reference gas (such as air in a sealed chamber). The

thermistors are mounted so that they are in close proximity

to the stainless steel (or Hastelloy®) walls of the sample

chamber. The entire transmitter is temperature-controlled,

and the thermistors are heated to an elevated temperature

in a constant-current Wheatstone bridge. The thermistors

lose heat to the walls of the sample chamber at a rate that is

proportional to the thermal conductivity of the gas surrounding

them. Thus, each thermistor will reach a different equilibrium

temperature. The temperature difference between the two

thermistors is detected in the Wheatstone bridge, and the

resulting bridge voltage is amplified and converted to a linear 4

to 20 mA output proportional to the concentration of one of the

constituents of the binary or pseudo binary gas mixture.

Features

• Ultra-stable glass-coated thermistors

• Single or dual gas push-button calibration

• PC interface package for digital output

• Type IP66/4X construction

• ATEX, IECEx, FM and CSA certified for Zone I

and Division 1 hazardous areas

The microprocessor-based XMTC is a compact, rugged,

online thermal conductivity transmitter that measures the

concentration of binary gas mixtures including hydrogen,

carbon dioxide, methane, helium and many others. The analyzer

also combines computer enhanced signal measurement with

fast-response software, real-time error detection and digital

communication via an RS232 or RS485 interface.

Applications

A thermal conductivity gas transmitter for use

in the following industries and applications:

Metals industry

H2 in N2 atmosphere in metal heat-treating furnaces

Electric power industry

H2 in cooling systems for generators

Petroleum industry

H2 in hydrocarbon streams

Chemical industry

• H2 in ammonia synthesis gas

• H2 in methanol synthesis gas

• H2 in chlorine plants

Methane industry

• CO2 in methane

Landfill/biogas industry

• CO2 in biogas

• CH4 in biogas

Gas production industry

Purity monitoring of argon, hydrogen, nitrogen and helium

Food Industry

CO2 in fermentation processes