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Operating Manual

Fast Thermal Conductivity Detector

FTC110-TRA/mA

Version 12_09 © Messkonzept GmbH

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Operating Manual 2

Messkonzept GmbH · Niedwiesenstr. 33 · 60431 Frankfurt · Germany

1. Features

• Precise and long term stable thermal conductivity measurement

•

High sensitivity independent of ambient temperature• Fast response with a T90 time of about 1 sec

• Measurement independent of gas flow and pressure in a wide range

• Small (105x50x50mm) and robust transmitter (protection class: IP65)

• Linear signal output e.g. ranging from 4mA for N2 to 20mA for H2

• Easy calibration routine using two potentiometers

2. Applications

The thermal conductivity of a gas mixture depends on the individual gas componentsand on the composition of the mixture. Under certain conditions, therefore, theconcentration of individual gas components can be determined by measuring the thermalconductivity. In other cases the identification of certain properties of gases is of specialinterest e.g. for quality control or safety reasons. Often these properties are related to thethermal conductivity and thereby identified.

The concentration can be determined with higher precision if one of the following conditionsis met:(a) The gas mixture consists of only two components, for example measuring O2 in Ar or H2

in N2.(b)

The gas mixture consists of more than two components but only concentrations of twocomponents vary, for example measuring CO2 in air.

(c) The gas mixture consists of more than two components but the component of interesthas a thermal conductivity that is very different from the other components (quasi-binary mixtures), for example monitoring impurities in H2.

3. Description

The thermal conductivity detector FTC110-TRA/mA is designed for industrial process gasanalysis. It is based on a micro-mechanical silicon chip which precisely measures the

thermal conductivity of the measuring gas. The chip is fitted into a stainless steel housingthat guarantees a pressure resistance up to 10 bar. In order to allow a temperature controlledoperation mode of the detector, the temperature of the stainless steel housing is controlledusing two heating elements and a temperature sensor that are attached to the housing. Thedefault value of the temperature is 60°C.

The stainless steel housing, the temperature control circuit and the electronics that generatesthe output signal are placed in a sealed aluminum housing (protection class: IP65). Thehousing is filled with small glass beads in order to avoid an explosion-capable mixture insidethe housing. Gas inlet and outlet are made of 6mm outer diameter stainless-steel tubing.

Warning: Do not open the aluminum housing!

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4. Technical Data

4.1 Absolute maximum ratings: min. typ. max. UnitsAmbient temperature -20 --- +55 °CSensor temperature --- +60 +75 °CGas pressure (absolute) 0.4 1 10 bar4.2 Specifications: min. typ. max. UnitsWeight (without cable) --- ~650 --- gGas flow 5 50 150 l/hT90 time at a flow of 100 l/h ---

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6. Electrical Connection

On the back of the aluminum housing there is a 4-pin female connector called connector 1 inthe diagram above. The pin code is given in the diagram. The color code of the cable isgiven below:

Color Connection

white - 24V DC Power Supply

brown + 24V DC Power Supply

green + 20mA Output

yellow - 20mA Output

black Shield

Warning: Do not interchange common and plus wires. This causes serious damage to theelectronics.

Specifications:

Description Range Recommended Current

Power Supply 18V to 24V DC 24V DC up to 450mA

Output Signal 4-20 mA

Burden 800 Ohm

The output signal is linear.

7. Calibration

Warning: All adjustments described in this chapter should only be performed by personnelwho are familiar with the FTC110 detector. An incorrect calibration results in erroneous

measurement.

The FTC110 transmitter is easily calibrated using two potentiometers. In general, it issufficient to check the zero point of the FTC110 detector. It is recommended to do this everymonth. Supply the zero gas to the sensor and wait for 15 min. Watch the output signal. Ifthe deviation is less than 1% from the measuring span of 16mA (0.16mA), the operation isstill okay and the transmitter can be used without further calibration.

If the deviation is more than 1% from 16mA (0.16mA), open the zero-adjust screw andcarefully store the screw and the small O-ring seal. Use a small screw driver in order to adjust

the zero potentiometer so that an output of 4mA is achieved.

In order to check the span, supply the span gas to the detector for at least 15 min. If thedeviation is less than 1% from 16mA (0.16mA), the operation is still okay and the

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transmitter can be used without further calibration. Otherwise open the span-adjust screwand adjust the span potentiometer so that an output of 20mA is achieved.

Warning: Be sure to reinstall the screws and O-ring seals after the calibration process.Otherwise the IP65 protection degree will be lost.

8. Measurement Specifications

T90 time

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