Single Gas Instrument Service Manual
Instruction 0019-9166
Bacharach, Inc.
Page
9
2.4
Sensor
Replacement
When the instrument can no longer be spanned, as described in Section “3.0 Sen-
sor Calibration,” the Sensor has reached the end of its useful life, and should be
replaced. The life of a Sensor is typically two years. The Sensor may also need
to be replaced if the instrument will not zero properly, or if erratic gas readings
occur. Refer to Section “4.0 Troubleshooting Chart.”
Equipment Needed (Refer to Section “5.0 Replacement Parts” for Part
Nos.):
•
Phillips-head screwdriver, No. 1
•
Replacement Sensor:
•
Nutdriver, 4mm (5/32")
•
Dioxor II - SO
2
•
Screwdriver, 1/8"
fl
at blade
•
Monoxor II - CO
•
O-Ring and Membrane, if required
•
Nonoxor II - NO
X
•
Monoxor II H - CO
Procedure:
WARNING!
Burn hazard! The Sensors contain corrosive chemicals,
DO NOT puncture or take the sensors apart.
1. Open the case as described in Section “2.1 Opening the Case.”
2. Using a nutdriver, loosen the nuts that secure the sensor wires to the Sen-
sor terminals R, S and C; then remove the wires. If the Sensor has pin and
socket connections, simply pull the sockets from the sensor pins.
3. Using
a
fl
at-blade screwdriver, remove the three screws and nuts that secure
the Sensor to the chamber assembly; then remove the Sensor along with its
O-ring and Membrane from the chamber assembly.
4. Remove and discard of the old Sensor in accordance with local and federal
regulations. DO NOT discard the sensor’s O-ring and Membrane, unless you
intend to replace these items.
NOTE:
Replace the O-ring if it looks deformed, and replace the
Membrane if it is contaminated with oil or dirt. We recommend
that both the O-ring and Membrane be replaced at the same time.
5. Remove the new Sensor from its shipping canister. Do not remove the short-
ing wire (across the R & S terminals) from the Sensor (SO
2
& CO only, the
NO
X
does not have a shorting wire) until you are ready to make the electrical
connection.
6. Position the Membrane, O-ring, and new Sensor on the chamber assembly
as per Fig 2-2. Ensure that the sensor terminals are positioned as shown.
Secure these items to the chamber assembly using the screws and nuts re-
moved in Step 3 (Torque to 4–8 oz. in.).
DO NOT overtighten the screws!
7. Remove the shorting wire from the R & S terminals (SO
2
& CO only). Con-
nect the
blue
(S),
red
(R), and
black
(C) wires from the P.C.B. to their as-
sociated sensor terminals (See Fig 2-4).
If the Sensor uses nuts to secure the
Sensor wires, DO NOT overtighten these connections!
8. Close the case as per Section “2.2 Closing the Case.”
9. Calibrate the new Sensor as per Section “3.0 Sensor Calibration.”
