Interscan’s sensors are designed to provide optimum performance for each individual gas. Thus, sensor formulations will vary from gas to gas, and even from range to range within a gas type.

The table below details sensor response data:   rise and fall times for new sensors, without any scrubber or filter in line. Note that rise time data is shown for both 90% response to final value, and 50% response to final value. The 50% figure is useful when considering how fast an instrument will respond in a critical (alarm) situation, whereby “full” response is not as important as the “step” response to an immediately hazardous concentration of toxic gas.

Sensor rise and fall times are affected by many factors, including age, chemisorption, cumulative exposure to target gas and interfering gases, and maintenance.

System lag time, reflecting the time for gas sample to travel through interconnect tubing, from a remote point back to the analyzer, can be estimated as follows:

100 feet (30.48 m) of Part No. 2140505 Bev-A-Line tubing, as supplied by Interscan, contains a volume of 0.241 liters. Assuming a flow rate of 0.5 liter/minute, it will take 29 seconds for the remote sample to traverse the tubing.

In general,

  • For every foot of tubing length, figure 0.29 seconds of travel time
  • For every meter of tubing length, figure 0.95 seconds of travel time

Various methods are available to limit lag time, including sampling at a higher flow rate and bleeding off to the analyzer, and incorporating heavier duty pumps and wider bore tubing.

For further information, please contact the factory.           Note that the following tabular data is currently undergoing revalidation.   Please contact the factory for the latest rise/fall time particulars.

 

GAS 
RISE TIME TO 90% (SEC)
RISE TIME TO 50% (SEC)
FALL TIME TO 10% (SEC)
Br2
30
5
20
CO
45
10–20
30
Cl2
30
5
20
ClO2
20–25
5
20
C2H4
60–120
40–50
≤ 180
EtO
60–120
40–50
≤ 180
HCHO
30–45
5–10
30–45
hydrazine(1)
120–180
≤ 100
180
hydrazine(2)
60–120
≤ 60
≤ 120
H2
≤ 60
5–10
45
HBr
30
20
30
HCl
45
20
30
HCN
20
5
20
H2O2
45
10
30–45
H2S(3)
20
5
30
H2S(4)
45
10–20
30
NO
20
2–5
20
NO2
15
2–5
15
O3
20–30
5
20
Peracetic acid
45
10
30–45
PrO
60–120
40–50
≤ 180
SO2
30
2–5
20
 

(1) Data shown for instruments with range =0–500 ppb
(2) Data shown for instruments with range >0–500 ppb
(3) Data shown for instruments with range =0–5 ppm
(4) Data shown for instruments with range >0–5 ppm