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MODEL 242
EXTENSION CABLE HOOK UP
1. Do not run sensor cable in conduit or open trays
with A.C. power wiring. Do not route sensor cable
near heavy electrical equipment.
2. For best sensor/instrument loop performance, use
factory-terminated extension cable (PN 23909-00).
(Using a different cable can introduce noise into
the signal and/or reduce loop accuracy.)
3. One end of extension cable (PN 23909-00) has 8
wires, and the other end has 11 wires. Refer to
Figure 1-9. The end with 8 wires goes into the junc-
tion box. The end with 11 wires goes to the instru-
ment. The extension cable enters the junction box
through the open side of the female threaded tee.
Use of conduit, the optional cable connector (PN
9310137), or other strain relief device to protect the
cable is at the discretion of the customer and
should comply with applicable agency guidelines.
If starting with unprepped cable (PN 9200276), remove
only as much insulation as is necessary. The instru-
ment end needs 11 leads: four leads from the green-
white-black-drain bundle, three from each of the two
coaxial cable bundles (the inner conductor, the insulat-
ing braid, and the drain wire), and one from the outer-
most overall braided-copper shield. For the junction
box end, only 8 leads are used: the white coaxial con-
ductor, its braided shield, the green coaxial conductor,
its braided shield, its drain wire, and the green, white,
and black conductors from the green-white-black-drain
bundle. The remaining shields and drain wires are not
used on the junction box end and should be removed -
- they should NOT be connected.
10
NOTE
FIGURE 1-9. Extension Cable
4. Connect the 8 wires of the extension cable to the
terminal block inside the sensor junction box as
indicated in Figure 1-7. Note: If all process meas-
urements will be less than 10,000 µS/cm, connect
the green wire from the black-green-clear wire bun-
dle of the extension cable to the terminal receiving
the orange sensor wire. See Figure 1-7.
5. Connect the 11 wires of the instrument-end of the
extension cable according to the applicable dia-
gram from Figures 1-10 through 1-15.
1.5 CALIBRATION
After sensor and transmitter/analyzer wiring is com-
pleted, calibrate the sensor.
Most analyzers require the input of the approximate
sensor cell constant before the analyzer calculates the
true cell constant. The nominal cell constant of the
Model 242 sensor depends on the size of the sensor
and the terminal to which the receive wire of the inter-
connecting cable is attached. Refer to Table 1-1 for
the appropriate nominal cell constant value.
TABLE 1-1: Nominal Cell Constants for 242 Sensors
Sensor Size
Black
1", DN 25
20
1.5", DN 40
9.0
2", DN 50
5.0
3", DN 80
4.0
4", DN 100
2.3
* The table gives the cell constant when the green receive
wire (from black-green-clear bundle) of the interconnect-
ing cable is attached to either the black wire terminal or
the orange wire terminal in the sensor junction box. See
Figures 1-7 and 2-1.
SECTION 1.0
MODEL 242 SENSOR
NOTE
Cell Constant (/cm)*
Orange
2.0
0.90
0.50
0.40
0.23
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