Emerson Process Management 53eA Simulating Inputs Other Amperometric Measurements

MODEL 54eA	SECTION 16.0
	TROUBLESHOOTING

16.12 SIMULATING INPUTS - OTHER AMPEROMETRIC MEASUREMENTS

To check the performance of the controller, use a decade box and a battery to simulate the current from the sen- sor. The battery, which opposes the polarizing voltage, is necessary to ensure that the sensor current has the cor- rect sign.

NOTE

It is not possible to simulate an input from a 498CL-01 sensor.

A.Disconnect the anode and cathode leads from terminals 1 and 2 on TB3 and connect a decade box and bat- tery as shown in Figure 16-2. It is not necessary to disconnect the RTD leads.

B.Set the decade box to the resistance shown in the table.

Sensor	Polarizing Voltage	Resistance	Expected current
499ACL-01 (free chlorine)	200 mV	28 MΩ	500 nA
499ACL-02 (total chlorine)	250 mV	675 kΩ	2000 nA
499ACL-03 (monochloramine)	400 mV	3 MΩ	400 nA
499AOZ	250 mV	2.7 MΩ	500 nA

C.Note the sensor current. It should be close to the value in the table. The actual value depends of the voltage of the battery. To view the sensor current from the main display, press any key to enter the main menu. Move the cursor to "Diagnostics" and press Enter (F4). The

sensor current is the second line in the display. Note the units: μA is microamps, nA is nanoamps.

D.Change the decade box resistance and verify that the correct current is shown. Calculate current from the equation:

Vbattery - Vpolarizing (mV)

current (μA) =

resistance (kΩ)

The voltage of a fresh 1.5 volt battery is about 1.6 volt (1600 mV).

FIGURE 16-2. Simulate Chlorine and Ozone

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