| Type | TGS | VQ | GOW | 
|---|---|---|---|
| Measurement method | Semiconductor | Heat reduction | Thermal conductivity | 
| Measurement range | ppm ranges to 100 % LEL  | 
            ppm ranges to 100 % LEL  | 
            from 0-5 Vol% to 0–100 Vol %  | 
        
| Percentage error  of f.s.d.  | 
            ±5 % | ±3 % | ±5 % | 
| Temperature range | -25 °C to +55 °C | -25 °C to +55 °C | -25 °C to +55 °C | 
| Temperature effect | 3 % | 2 % | 3 % | 
| Response time (t90) | approx. 55 s | approx. 40 s | approx. 55 s | 
| Pressure effect | 1 % | 1 % | 1 % | 
| Mounting position | optional | optional | optional | 
| Application | Poisonous, combustible and explosive gases in the LEL?region  | 
            Poisonous, combustible and explosive gases in the LEL?region  | 
            Gases exhibiting substantial differences in thermal conductivity, compared to air  | 
        
| Versions available | industrial (Al), industrial (VA)- and Ex-version  | 
            industrial (Al), industrial (VA)- and Ex-version  | 
            industrial (Al), industrial (VA)- and Ex-version  | 
        
| Expected lifetime  of the sensor  | 
            unlimited, when used  for gases not causing catalytic poisoning  | 
            unlimited, when used  for gases not causing catalytic poisoning  | 
            unlimited, when used with gases that do not attack aluminium, rhenium-tungsten or gold | 
| Dimensions  (W x H x D)  | 
            150 x 175 x 105 mm | 150 x 175 x 105 mm | 150 x 175 x 105 mm | 
 
| Type | TOX | IR | PID | 
|---|---|---|---|
| Measurement method | Electro-chemical reaction | Infrared | Photo-Ionisation | 
| Measurement range | ppm ranges to 0–100 Vol %  | 
            0-100 %  LEL CH4, C3H8,  C2H2, 0-100 Vol % CH4 0 –1, 2, 3, 4, 5 Vol % CO2  | 
            0 – 200 ppm to 0 – 2.000 ppm  | 
        
| Percentage error of f.s.d. | ±3 % | ±2 % | ±5 % | 
| Temperature range | -25 °C to +55 °C | -25 °C to +55 °C | -25 °C to +55 °C | 
| Temperature effect | 2 % | 2 % | 3 % | 
| Response time (t90) | approx. 60 s | approx. 45 s | approx. 120 s | 
| Pressure effect | 1 % | 4 % | 1 % | 
| Mounting position | optional | optional | optional | 
| Application | O2, CO, NH3, NO2, SO2, H2S and others | CH4 (Vol %; LEL) Propan (LEL), CO2 (Vol %) | e.g. C7H8,  C8H10 CHCl3, PH3  | 
        
| Versions available | industrial (Al), industrial (VA)- and Ex-version  | 
            industrial (Al), industrial (VA)- and Ex-version  | 
            industrial (Al), industrial (VA)- and Ex-version  | 
        
| Expected lifetime  of the sensor  | 
            12 months to 5 years depending on the measuring cell  | 
            approx. 5 years | 12 months | 
| Dimensions (WxHxD) | 150 x 175 x 105 mm 150 x 200 x 105 mm (O2)  | 
            150 x 175 x 105 mm | 150 x 175 x 105 mm | 
Technical data – for all 3  basic versions of gas transmitter
| Type | GTR 210 Ex-Version | GTR 210 Standard | GTR 210 Comfort | 
|---|---|---|---|
| Supply voltage | 24 V DC +10% / -25% | 24 V DC +10% / -25% | 230 V AC, 50 Hz 115 V AC, 60 Hz (optional)  | 
        
| Power consumption | 4 W | 4 W | 10 VA | 
| Interface | 3-wire techniques with current interface 4 – 20 mA | 3-wire techniques with current interface 4 – 20 mA or LON®-4-wire techniques | 1 current output 4 – 20 mA 4 potential-free changeover contact for alarm/failure 1 digital input for cancelling alarms  | 
        
| Type of protection | II 2G Ex d e ia mb IIC T4 Gb  | 
            none | none | 
| Ex-version | ATEX certificate:   DEKRA 11 ATEX 0257 X IECEx certificate: IECEx DEK 11.0090 X  | 
            ||
| Protection class | IP 54 | IP 54 | IP 54 | 
| Weight | 2,3 kg | 1,8 kg | 2,0 kg | 
 
By employing 6 different types of sensor, noxious, explosive and non-combustible  gases and vapours can be measured.
Display of the measured gas  concentration and the adjustable alarm thresholds, are shown on a multi-colour  graphic display. The keyboard input is by way of a touchpad.
A current  signal is generated that is proportional to the measured concentration of gas,  which is transmitted to an evaluation unit placed in a safe area, away from any  dangers of explosion.
TOX sensor
The TOX sensor is a measurement system with electro-chemical cell, where the  sampled gas is measured by diffusion. In the case of oxygen measurement the  oxygen content is in an electrolyte, thus producing a small flow of current  (electro-chemical process).
At a constant air pressure, this current is  directly proportional to the oxygen concentration in the sampled air.

1 = Anode
2 = Electrolyte
3 = Cathode
4 = Diffusion  path
5 = Diffusion filter
6 = Test gas


1 = Infrared-radiating source
2 = Test gas
3 = Diffusion  filter
4 = Infrared-detector
5 = Measurement chamber
GOW sensor
The GOW sensor functions on the principle of thermal conductivity. Two  rhenium-tungsten resistors are used as a measuring element, where the comparison  element is subjected to normal ambient air and the measuring element is  subjected to the test gas. Any change in the concentration of gas at the  measurement element, causes a change in temperature, which is due to the  variation of conductivity.
The resultant change in resistance is a direct  measure of the gas concentration.

 
1 = Diffusion filter
2 = Test resistor
3 = Comparsion  resistor
The PID sensor
The sampled gas flows through a measurement chamber, that incorporates a UV  radiating source and a pair of
electrodes with opposing polarity. The gas  molecules to be detected are ionized by the UV radiation.
The resulting  positively charged molecules and the electrons are attracted to the relevant  electrode. The current generated is a measure of the gas  concentration.
Using the PID measuring head, volatile organic compounds  (VOC) can be measured, the ionisation potential of which is less than the energy  in the UV radiating source (10,6 eV), e.g. aromatic hydrocarbons like toluol  (C7H8) and xylene (C8H10) as well as  chlorinated hydrocarbons like trichloroethylene (CHCl3). The  detection of toxic gases like phosphine (PH3) is also possible.

 
1 = UV radiating source
2 = Test gas
3 = Capacitive  charge
 
VQ sensor
The head of the VQ sensor functions on the principle of heat reaction. When  combustible or reducing gases or vapours come in contact with the measuring  element, they are subjected to catalytic combustion, which causes a rise in  temperature; this rise causes a change in the resistance of the measuring  element which is used as a measure of the component of gas being tested.
The  inert element is for compensating the temperature and conductivity of the test  gas.

1 = Catalyzer pellistor
2 = Electric connections
3 = Inert  pellistor
4 = Diffusion filter