Chapter 4 Maintenance; Electrode Cleaning; Automatic Temperature Compensator - Emerson Rosemount 389 Instruction Manual

4 Maintenance
Rosemount 389/389VP sensors require minimum maintenance. Keep the sensors clean
and free of debris and sediment at all times. The frequency of cleaning by wiping or
brushing with a soft cloth or brush is determined by the nature of the solution being
measured. Remove sensors from the process periodically and check them in buffer
solutions.
WARNING!
PRESSURE AND TEMPERATURE
Before removing the sensor, be absolutely certain that the process pressure is reduced to 0
psig and the process temperature is lowered to a safe level!
If the sensor will not calibrate, refer to your transmitter manual for proper test procedures.
If you determine that the sensor has failed, discard and replace it.
4.1

Electrode Cleaning

If the electrode is coated or dirty, clean as follows:
1.
2.
3.
4.
4.2

Automatic Temperature Compensator

The temperature compensator element is a temperature sensitive resistor and can be
checked with an ohmeter. Resistance increases with temperature.
Instruction Manual
Remove the sensor from process.
Wipe the glass bulb with a soft, clean, lint free cloth or tissue. If this does not remove
the dirt or coating, go to Step 3 (detergents clean oil and grease; acids remove
scale.)
Wash the glass bulb in a strong detergent solution and rinse it in clean water. If this
does not clean the glass bulb, go to Step 4.
WARNING!
CORROSIVE SUBSTANCE
The solution used during the following test is an acid and should be handled with care.
Follow the directions of the acid manufacturer. Wear the proper protective equipment.
Do not let the solution come in contact with skin or clothing. If contact with skin is
made, immediately rinse with clean water.
Wash the bulb in a dilute 5% hydrochloric acid solution and rinse with clean water.
Soaking the sensor overnight in the acid solution can improve cleaning action.
Replace the sensor if it cannot be cleaned.
Maintenance
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