Walchem W100 User Manual

CAUTION: There are live circuits inside the controller even when the power switch is in the
OFF position! Servicing and troubleshooting the controller must be performed by
Qualified
Service Personnel.
1
W100/W600/W900 Controller
pH Electrode Troubleshooting Guide
Table of Contents
Section 1
Electrode Reading Responds Slowly
Section 2
Electrode Reading is Stuck on one Value
Section 3
Electrode Reads Low or High Versus a Calibrated Handheld Meter; Cannot Calibrate
Section 4
Electrode Fault
Section 5
pH Reading is Unstable
Note: pH electrodes are like batteries and their output voltage will change with time, even if they are not being
used. The useful life of a pH electrode is limited, and that time varies with the conditions it’s exposed to in the
application. Electrode life may be as short as one week in some aggressive applications (extreme temperature, pH
and/or pressure, dirty water, harsh chemicals) or more than a year in other applications with potable quality water at
room temperature.

Walchem W100 Specifications

General

Model	W100
Type	Controller
Display	LCD
Input Type	Analog/Digital
Inputs	4
Outputs	4
Analog Outputs	2
Analog Inputs	2
Digital Inputs	2
Power Consumption	10 W
Communication Protocol	Modbus RTU
Communication	RS-485
Weight	1.5 kg
Output Type	Analog
Power Supply	100-240 VAC
Enclosure	IP65
Storage Temperature	-20 to 70 °C
Humidity	0 to 95%
Dimensions	144 x 144 mm

Summary

Electrode Reading Responds Slowly

Electrode Cleaning and Calibration Procedures

Details procedures for cleaning and calibrating pH electrodes based on coating type.

Electrode Replacement for Unresponsive Readings

Action taken if electrode cleaning does not improve response time.

WEL-PH Housing: Electrode Reading Stuck

Normal WEL-PH Housing Readings

Expected readings for WEL-PH housing in various connection states.

Troubleshooting Stuck WEL-PH Readings

Checks for shorts, opens, or broken glass causing stuck readings.

WEL Transmitter Housing: Electrode Reading Stuck or Erratic

WEL Transmitter Housing Normal Readings

Expected readings for WEL Transmitter Housing with specific fault conditions.

WEL-PH Housing: Low/High Readings or Calibration Failure

pH vs mV Reading Correlation

Explains the expected mV change per pH unit for electrode readings.

Temperature Compensation and Verification

Checks ATC function, temperature element programming, and resistance correlation.

WEL-PH Housing: Calibration Failure Details

Checking Calibration Gain and Offset

Verifies calibration gain and offset values are within acceptable ranges.

Resetting Calibration Values

Procedure to reset calibration values to a starting point.

WEL Transmitter Housing: Low/High Readings or Calibration Failure

pH vs mA Reading Correlation

Explains the expected mA signal range for pH readings.

Checking mA Signal from Sensor

Procedure to measure mA signal coming from the sensor using a multimeter.

WEL-PH Housing: Electrode (Sensor) Fault

Electrode Fault Troubleshooting

Identifies causes and corrective actions for 'Electrode Fault' errors.

Controller Board Error Troubleshooting

Identifies causes and corrective actions for board recognition errors.

WEL-PH/WEL Transmitter Housing: Unstable Reading

Stabilizing Readings in Beaker

Procedure to check if electrode reading stabilizes in a beaker.

Troubleshooting Unstable Readings

Checks for ground loops, electrical interference, or power supply issues.