TGS2442 Datasheet, PDF (22/25 Pages) List of Unclassifed Manufacturers – Detection of Carbon Monoxide

CALIBRATION OF TGS2442
Calibration
Preheat sensor
Pre-calibration ^*
Burn-in detector
Set microcomputer to
Calibration Mode
* Selection of RL - Sec. 3-2(a)
β grade compensation - Sec. 3-2(b)
Signal Processing in the Microcomputer
Insert into gas chamber
Expose to 100ppm CO
Power reset ON
Vent gas
Adjust VRadj
main calibration
Begin Calibration Mode
Step 1
Sensor stabilization
Step 2
Sample V1 (sensor output)
and V4 (thermistor output)
Step 3
Calculate ƒ(Rs)
Determine KTemp
Calculate ƒ(Rs^x) (100) and store in memory
Step 4
Continuous sampling of V3 (reference voltage)
Calculate ƒ(Rref) continuously
Adjust ƒ(Rref) to the threshold value
Deactivate Calibration Mode
on microcomputer
End calibration
Figure 8 - Calibration and signal processing in the microcomputer
3-3. Main calibration (using “Calibration Mode” in the
microcomputer )
Using the mode selection port on the microcomputer,
Step 3:
Calculate ƒ(Rs), KTemp, ƒ(Rs^x) according to the
procedure in Section 2-3(a,b). The value f(Rs^x) is
select “Calibration Mode”. Switch the detector stored temporarily in the microcomputer’s RAM.
ON␣ (Reset), activating calibration mode. Signal Step 4:
processing in the microcomputer during the After ventilating the calibration gas, V3 is
calibration mode proceeds as shown in Figure 8. Place continuously monitored and converted to ƒ(Rref) [see
the detector in a vessel which is then filled with equation in 2-3(c)]. Using a potentiometer (VRadj),
100ppm of CO.
adjust ƒ(Rref) to equal ƒ(Rs^x) in 100ppm of CO which
Step 1:
Stabilize sensor output V1 in 100ppm of CO for the
predetermined period stored in the microcomputer.
Step 2:
was memorized in Step 3. This procedure can be
simplified by directing the microcomputer to activate
an LED when ƒ(Rref) is set to the correct level.
For example: If ƒ(Rref) = [ƒ(Rs^x)(100ppm)] ± 3%,
Obtain V1 and V4 at the conclusion of stabilization.
then “LED TURN ON” else “LED TURN OFF”
Revised 04/01
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