User guide

Application Guide | Gas detection in refrigeration systems
© Danfoss | DCS (MWA) | 2018.05 DKRCI.PA.S00.A1.02 | 520H12772 7
Sensor response time
The response time is the elapsed time for a sensor
to read a given percentage of the actual value for
a step change in the target gas concentrations.
Response time for most sensors is given as t
90
,
meaning the time that it takes the sensor to read
90% of the actual concentration. Fig. 4 shows an
example of a sensor with a reponse time t
90
of 90
seconds.
As shown in the graphic, the sensor reaction
above 90% becomes slower and takes longer to
read the 100%.
Fig. 4: Sensor with a response time t90 of 90 seconds
GAS Sensor technology Response time t
90
, seconds
Ammonia
Electrochemical 0-100/ 0-300 ppm <40s
Electrochemical 0-1000ppm <40s
Electrochemical 0-5000ppm <40s
Semiconductor >120s
Pellistor <20s
Infrared Infrared <90s
Halocarbons Semiconductor >120s
Hydrocarbons Pellistor <15s
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Time, s
Fraction of Concentration Change
050 100 150 200
250