| 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 sec. | approx. 40 sec. | approx. 55 sec. | 
| Pressure effect (atm.) | 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 | 
| Service life 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 | 
| Supply voltage | 15 – 30 V | 15 – 30 V | 15 – 30 V | 
| Interfaces | 3-wire techniques 4-20 mA or LON© 4-wire techniques, galvanically isolated, data transfer 78 kB/s | 3-wire techniques 4-20 mA or LON© 4-wire techniques, galvanically isolated, data transfer 78 kB/s | 3-wire techniques 4-20 mA or LON© 4-wire techniques, galvanically isolated, data transfer 78 kB/s | 
| Protection Ex-Version  | 
            II 2 G Ex demb [ia] IIC T6 KEMA 03 ATEX 2403 X  | 
            II 2 G Ex demb [ia] IIC T6 KEMA 03 ATEX 2403 X  | 
            II 2 G Ex demb [ia] IIC T6 KEMA 03 ATEX 2403 X  | 
        
| Protection class | IP 54 | IP 54 | IP 54 | 
| Dimensions  (W x H x D)  | 
            150 x 170 x 105 mm | 150 x 170 x 105 mm | 150 x 170 x 105 mm | 
| Weight | 2,7 kg | 2,7 kg | 2,7 kg | 
| Type | TOX | IR | PID | 
|---|---|---|---|
| Measurement method | Electro-chemical cell | Infrared | Photo-Ionisation | 
| Measurement range | ppm ranges to  100 LEL %  | 
            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 sec. | approx. 45 sec. | approx. 120 sec. | 
| Pressure effect (atm.) | 1 % | 4 % | 1 % | 
| Mounting position | optional | optional | optional | 
| Application | O2, CO, NH3,  NO2, SO2, H2S a.o.  | 
            CH4 (Vol %; LEL) Propane (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  | 
        
| Service life of the sensor | 12 months to 5 years depending on the measuring cell | approx. 5 years | 12 monthss | 
| Supply voltage | 15 – 30 V | 15 – 30 V | 15 – 30 V | 
| Interfaces | 3-wire techniques 4-20 mA or LON© 4-wire techniques, galvanically isolated, data transfer 78 kB/s | 3-wire techniques 4-20 mA or LON© 4-wire techniques, galvanically isolated, data transfer 78 kB/s | 3-wire techniques 4-20 mA or LON© 4-wire techniques, galvanically isolated, data transfer 78 kB/s | 
| Protection Ex-Version  | 
            II 2 G Ex demb [ia] IIC T6 KEMA 03 ATEX 2403 X  | 
            II 2 G Ex demb [ia] IIC T6 KEMA 03 ATEX 2403 X  | 
            II 2 G Ex demb [ia] IIC T6 KEMA 03 ATEX 2403 X  | 
        
| Protection class | IP 54 | IP 54 | IP 54 | 
| Dimensions (WxHxD) | 
             100 x 180 x 80 mm  | 
            
             100 x 180 x 80 mm  | 
            
             100 x 180 x 80 mm  | 
        
| Weight | 1,1 kg | 1,1 kg | 1,1 kg | 
TGS sensor
The TGS sensor contains a semiconductor sensor, which is constructed on  SnO2-sintered N-substrate. When combustible or reducing gases are  absorbed by the surface of the sensor, the concentration of the test gas is  determined by the change in conductivity.



1 = Disffusion filter 
2 = Test resistor
3 = Comparison resistor

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