Technical data

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General Description

A fixed gas monitoring system consists of a transmitter and a controller (GMA), which are connected

by means of cable. The transmitter converts the gas concentration into an electrical signal and

transmits it over the cable to the controller for further processing.

Compared to the transmitter CC28, the model CC28 D provides an additional display, while the

CC28 DA features a display and a visual and audible alarm.

The comprehensive electronics allow easy operation and maintenance and also increases the

operational safety and accuracy. The special features of the transmitter are:

• Indication of concentration at display or at remote control

• Adjustment by means of touch keys or remote control, without opening of casing

• Compensation of temperature effects.

• Ex-Approval for use at temperatures from -20 to +50°C

• Function Approval for use at temperatures see sensor specification

• Smart Sensor system – sensor replacement by means of plug-in, pre-calibrated sensor

• Permanent status display (operation/fault) at transmitter

Detection Principle

The CC28 is operated on the detection principle "catalytic combustion" (fig. 1). The gas/vapour-air

mixture enters the sensor chamber by diffusion through the sinter filter. Inside the sensor chamber

there are an active and a passive sensor filament. The heated active sensor burns (oxidizes) the

entering gas at its vatalytic layer. This increases the temperature at the sensor and results in a change

of the electrical resistance, which is the measure for the gas concentration. The passive (reference)

sensor is exposed to the same ambient conditions as the active (detection) filament and is used for

compensation of environmental effects (e.g. temperature changes).

Detection principle - Catalytic combustion

Active element

Passive elemen

Sinter metal

Gas

Sensor

chamber

Fig. 1