ENMET SPECTRUM - Manual (Page 15)

SPECTRUM Series ENMET Corporation
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3.2.2 Sensor Removal and Replacement
A low 9v battery may cause a “Cell Out” indication. Check or replace the 9v Battery if “Cell Out” is displayed.
A sensor must be replaced when it no longer responds adequately to the target gas. This is indicated by a low gas
concentration reading when exposed to a known concentration of the target gas, and the inability to calibrate the
instrument, with a "C-FAULT" display after calibration. Expected sensor lifetimes in normal environments are given
in Table 1 Appendix A.
After removing the back of the enclosure, remove the circuit board and battery together, by sliding the circuit board
away from the switch surface while rotating it upward. Unplug the sensor from the circuit board.
C AUTION : New sensors may come with a shorting clip that must be removed for proper operation.
Remove the shorting clip (if present) from the new sensor and plug the new sensor in its
place. Allow the sensor to stabilize in the instrument with the power on for one hour before
recalibrating.
The initial calibration of a new sensor must be performed with electronics removed from the
instrument enclosure. Follow the procedure for calibrating the instrument as outlined in
Section 3.1.3 of this manual with the following modification.
Sensor Bottom View
N OTE : During this procedure make sure the O PAQUE calibration cup 02552-008 or B LUE 02552-023 stays centered
over the sensor. See Figure 5.
*C AUTION : Having the calibration cup too tight will cause the sensor to become deadheaded resulting in an inaccurate
calibration. See Figure 5.
During the application of the span gas, the counter counts down from an upper value given in Table 2. When
the counter gets down to 60, adjust the potentiometer located behind the horn on the instrument PC board, so
that the display to the right of the counter reads a little above the calibration voltage given for the target gas in
Table 2. As the counter continues, turn the pot so that the calibration voltage is reached when the counter
reaches 30. This is a one-time adjustment to align the sensor output with the instrument electronics. It should
only be performed upon sensor replacement. All future calibrations should follow the procedure in Section
3.1.3.
Remove the 3 red caps from the pushbutton switches. Replace the circuit board in the enclosure by sliding the
switches into their holes while rotating the circuit board downward; you may need to use your screwdriver to gently
guide the sensor into place. Replace the battery in its cavity. Replace the back cover of the instrument. Replace the
red caps on the pushbutton switches. Calibrate the instrument according to the procedure in section 3.1.3.
N OTE : that the sensor must be replaced with a sensor for the same target gas; the instrument cannot be changed to
detect a different target gas without modifications in addition to changing the sensor type.
Figure 5: Initial Calibration of Replacement Sensor
Spectrum PCB
Opaque, Calibration Cup
*Centered over Sensor
Sensor
Red Pushbutton Caps
3 places