Emerson Process Management 3081 pH/ORP instruction manual Voltage mV, 111

MODEL 3081 pH/ORP	SECTION 12.0
	TROUBLESHOOTING

12.8.2pH Simulation When the Preamplifier Is Located in the Transmitter.

1.Verify that switch S-1 is set to "transmitter". See Section 2.2.

2.Turn off sensor diagnostics. See Section 8.4.

3.Turn off automatic temperature compensation. Set manual temperature compensation to 25°C. See Section 8.5.

4.Disconnect the sensor and wire the transmitter as shown in Figure 12-7.

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 will appear in the temperature-output area. The main display will continue 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 properly.

7.If a standard millivolt source is available, remove the jumper between TB-7 and TB-10 and connect the voltage source.

8.Following the procedure in Section 7.5, 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.

FIGURE 12-7. pH Simulation When the Preamplifier Is Located in the Transmitter.

Voltage (mV)	pH
295.8	2.00
118.3	5.00
-118.3	9.00
-295.8	12.00

12.8.3pH Simulation When the Preamplifier Is Located in a Remote Junction Box or in a Sensor-Mounted Junction Box.

1.Verify that switch S-1 is set to "sensor or junction box". See Section 2.2.

2.Turn off sensor diagnostics. See Section 8.4.

3.Turn off automatic temperature compensation. Set manual temperature compensation to 25°C. See Section 8.5.

4.Disconnect the sensor and wire the sensor side of the junction box as shown in Figure 12-8. Leave the inter- connecting cable between the junction box and transmitter in place.

5.Attach a jumper between TB1-7 (REF IN) and TB1-10 (pH IN).

6.From this point on, continue with steps 6 through 9 in Section 12.8.2. For testing using a standard millivolt source, be sure to remove the jumper between TB1-7 and TB1-10 before connecting the standard mil- livolt source.

FIGURE 12-8. pH Simulation When the Preamplifier Is Located in a Remote

Junction Box or in a Sensor-Mounted Junction Box.

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