Emerson Rosemount5081, Instruction Manual, Page: 86 / 152

4. Disconnect the sensor and wire transmitter as shown in Figure 8-5 .
5. Attach a jumper between TB-7 (REF IN) and TB-10 (pH IN).
6. Measure the voltage. Press DIAG on the IRC.
The InPut voltage in millivolts appears in the temperature-output area. The main
display continues to show pH. The measured voltage should be 0 mV, and the pH
should be approximately 7. Because the calibration data in the transmitter may be
offsetting the input voltage, the displayed pH may not be exactly 7.0. If the actual
readings are close to expected, the transmitter is probably operating normally.
7. If a standard millivolt source is available, remove the jumper between TB-7 and
TB-10 and connect the voltage source.
8. Calibrate the transmitter. Use 0.0 mV for pH 7 ( bF1 ) and -177.4 mV for pH 10 ( bF2 ).
If the transmitter is working, it should accept the calibration.
9. To check linearity, leave autocalibration and return to the main display. Set the
voltage source to the values in the table and verify that the pH reading matches the
expected value.
Voltage (mV) pH
295.8 2.00
118.3 5.00
-118.3 9.00
-295.8 12.00
Diagnostics and troubleshooting
76 Rosemount 5081