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Model TS420
4
2.2 Control Electronics
The Model TS420’s electronics are contained within a plastic housing so that sensor
information can be processed at the point of detection. The Model TS420 provides a 4-20 mA
output signal proportional to 0 to 25% V/V O
2
full-scale gas concentration at the detector.
Ambient Air is approximate 20.9% V/V O
2
. This level equals 17.38 mA. As the oxygen level
decreases the 4-20 mA signal decreases.
The TS420 provides a two-digit LCD (Liquid Crystal Display). This display (Figure 3) provides
status such as gas present, fault and calibration cues to the operator. The MODE LCD is on
steady during normal operation to show that the sensor is functioning properly.
Monitored faults are: data memory failure, failed to calibrate and sensor removed.
Engineering specifications covering the sensor cell and control electronics are found in the
Appendix, Section 5.1.
Figure 3 LCD Display Location
DISPLAY
C
A
L
M
O
D
E