Emerson 54e pH/ORP Preamplifier Troubleshooting Procedure, Preamp in a junction box Figure

MODEL 54e pH/ORP

PREAMPLIFIER TROUBLESHOOTING PROCEDURE

Use this procedure when diagnosing the circuit which carries the signal from the sensor. There are 3 sepa- rate procedures, depending on where the preamplifi- er is located.

A. Preamp in a junction box (Figure 8-2)

1.Verify that the controller's preamp switch is in the sensor/J box position (see Figure 2-5).

2.Remove the cover of the junction box.

3.Disconnect the BNC adapter or remove leads from TB1-7 and TB1-10 (whichever is connect- ed).

4.Install a jumper between 7 and 10, 3 and 4, and 7 and 8 (see Figure 8-2).

5.The controller should now read approximately 7 pH.

NOTE

If the controller has been calibrated with a large zero offset, the pH may not be close to 7. In this case, standardize the con- troller at 7. (Section 3.4).

6.If the controller does not read correctly (after standardizing, if necessary), go to step B.

SECTION 8.0

TROUBLESHOOTING

B. Controller preamp check (Figure 8-3)

1.Disconnect all sensor wiring from the controller at TB2.

2.Verify that the preamp location switch is in the analyzer position, and that temperature compen- sation is set to manual at 25°C or 77°F (see Section 3.5).

3.Jumper TB2-3 to TB2-4 and TB2-7 to TB2-8.

4.Jumper TB2-7 to TB2-10 to simulate 7 pH.

5.The controller should now read 7 pH (or 0 mV in ORP mode).

NOTE

If the controller has been calibrated with a large zero offset, the pH may not be close to 7. In this case, standardize the con- troller at 7. (Section 3.4).

6.If the controller does not read correctly (after standardizing, if necessary), replace the con- troller.

7.If a millivolt source is available, it can be con- nected to TB2-7 and TB2-10 to simulate pH val- ues. Refer to Figure 8-1 for the relationship between mV and pH, sample values are +172 mV for 4 pH and -172 mV for 10 pH.

64