Operator Manual

748223-K June 2002

Model 7003M

d.Interfering Gases

Gases that are reduced or oxidized in the range of 0.5 to 0.8VDC contribute to sensor current and can cause a readout error. Only a few gases have this characteristic. Common gases that should be avoided include SO2, Cl2, and

oxides of nitrogen (NOX). Low-level concentrations of hydrogen sulfide tend to contaminate the sensor, but may not seriously affect oxygen measurement.

If you suspect that any stream components are affecting the operation of the sensor, contact Rosemount Analytical Technical Services.

If contaminated, the rechargeable sensor must be rejuvenated and the disposable sensor must be replaced. Refer to the instructions supplied with the sensor.

5-3 CIRCUIT DESCRIPTIONS

a.Signal Board

The Signal Board is configured to match the type of sensor ordered with the analyzer. If the type of sensor is changed, or the Signal Board is repaired or replaced, verify the rocker switch position (SW1):

Rechargeable Sensor: Close positions 1,4, and 5

Disposable Sensor: Close positions 2,4, and 6

b.Power Supply Board

The Power Supply Board provides:

•±12V (non-isolated) for analog signaling function

•+5V (isolated) for other functions for that circuit

There are isolated and non-isolated grounds on the Power Supply Board. TP1 is the non-isolated ground and should be used with TP6 and TP7.

c.Microprocessor Board

The Microprocessor Board is the functional center of the instrument. With the exception of the program chip, no user serviceable functions are on this assembly. If the Microprocessor Board is to be repaired or replaced, note the positions of the configuration jumpers for setting jumpers on replacement board.

An instrument timer circuit monitors instrument power for a power failure, power surge or other outside condition interfering with the microprocessor operation. When conditions return to normal, the circuit will attempt a system restart. If the microprocessor is still capable of operating, both alarm relays will be put into alarm condition, the screen will clear, and the output current will drop to 0 mA. Then the instrument will go through a normal power-up routine and will eventually return to routine operation with alarms and output restored to their normal conditions. The appropriate error code (E-0, etc.) will be displayed until the ACK button is pressed.

d.Alarm Circuits

Each alarm activation setpoint is designed to be at a different level from the deactivation setpoint:

•To prevent relay contacts from chattering if the oxygen level stays around the setpoint.

•+5V (non-isolated) for microprocessor and associated logic

•+24V (non-isolated) for the isolated current function

•To indicate to the microprocessor whether alarm is HIGH or LOW.

•To allow for a time lag between the time the alarm is activated and the time it is deactivated for ON/OFF- Control purposes.

5-2 Routine Servicing and Troubleshooting

Rosemount Analytical Inc. A Division of Emerson Process Management