Walchem WDSW100 User manual

Five Boynton Road Hopping Brook Park Holliston, MA 01746 USA
TEL: [phone] WEB: www.walchem.com
Disinfection Sensors
Instruction Manual

Notice
© 2018 WALCHEM, Iwaki America Inc. (hereinafter “Walchem”)
Five Boynton Road, Holliston, MA 01746 USA
[phone]
All Rights Reserved
Printed in USA
Proprietary Material
The information and descriptions contained herein are the property of
WALCHEM. Such information and descriptions may not be copied or
reproduced by any means, or disseminated or distributed without the
express prior written permission of WALCHEM, Five Boynton Road,
Holliston, MA 01746.
Statement of Limited Warranty
WALCHEM warrants equipment of its manufacture, and bearing its identification
to be free from defects in workmanship and material for a period of 24 months
for electronics and 12 months for mechanical parts and electrodes from date of
delivery from the factory or authorized distributor under normal use and service
and otherwise when such equipment is used in accordance with instructions
furnished by WALCHEM and for the purposes disclosed in writing at the time of
purchase, if any. WALCHEM’s liability under this warranty shall be limited to
replacement or repair, F.O.B. Holliston, MA U.S.A. of any defective equipment
or part which, having been returned to WALCHEM, transportation charges
prepaid, has been inspected and determined by WALCHEM to be defective.
Replacement elastomeric parts and glass components are expendable and are not
covered by any warranty.
THIS WARRANTY IS IN LIEU OF ANY OTHER WARRANTY, EITHER
EXPRESS OR IMPLIED, AS TO DESCRIPTION, QUALITY,
MERCHANTABILITY, and FITNESS FOR ANY PARTICULAR PURPOSE OR
USE, OR ANY OTHER MATTER.
P/N 180307.W
March 2018

Table of Contents
1.0 Introduction .....................................................1
Sensor 1
Flow Cell 1
2.0 Installation .......................................................2
Assembling the Sensor 2
Flow Cell Placement 4
Installing Sensor into Flow Cell 5
Sensor Parts Exploded View 6
Typical Installation 7
Wiring Instructions 8
3.0 Operation .......................................................13
Conditioning 13
Calibration 13
4.0 Troubleshooting............................................15
The disinfectant reading is much lower than the manual
analysis 15
The disinfectant reading is much higher than the manual
analysis 16
Sensor Error 16
Disinfectant Reading is Unstable 16
Calibration Failure 17
5.0 Maintenance ..................................................18
Cleaning the Membrane 18
Replacing the Membrane 18
Sensor Storage 19
6.0 Specifications................................................20
7.0 Sensor Part Numbers ...................................24

1
1.0 Introduction
The Walchem disinfection sensors consist of an amperometric
sensor assembly and a flow cell. Assembly of these parts is
required, so please read these instructions carefully. The sensor is
capable of measuring the disinfectant in clean water or in water
contaminated with debris thanks to our unique flow cell design.
WDSW100, WCNP100, WDS600, W900 and WebMaster series
controllers with amperometric chlorine sensors can be used for
reporting chlorine residual measurements in accordance with EPA
Method 334.0.
The standard (part numbers 104010,191300, 191441, 191530 &
191587) free chlorine/bromine sensor membrane is not compatible
with water containing surfactants!
Sensor
The sensor assembly includes the sensor body, a replaceable
membrane cap, a 100-ml bottle of electrolyte fill solution, and
special abrasive paper. Make sure that all parts are included.
The oxidizer molecules diffuse through the membrane and in the
acidic environment of the electrolyte fill solution, a redox reaction
occurs at the electrodes in the sensor. The current generated by this
reaction is converted to a robust voltage signal that is linear with the
concentration of the oxidizer.
Flow Cell
The flow cell consists of a translucent flow cell body, mounting nut
and o-ring, washer set and o-ring. Make sure that all parts are
included.
The flow cell is required to prevent bubble formation on the
membrane and to provide proper flow velocity across the face of the
membrane. The sensor will not read accurately if it is not installed
in the flow cell, with a flow rate between 30 and 100 liters per hour,
at an operating pressure of 1 atmosphere or less. The ¼” adapter
must NOT be removed from the flow cell.

2
2.0 Installation
Assembling the Sensor
CAUTION: Wear gloves and safety glasses during assembly of
the sensor since the electrolyte is a STRONG ACID. It is
recommended to perform this operation over a sink with running
water available. After using, re-cap any remaining electrolyte and
store the bottle upside-down until the next use.
Standard Free Chlorine/Bromine Sensors (part numbers 104010,
191300, 191441, 191530 & 191587)
1. Clean just the tip of the working electrode with the special abrasive
paper supplied. Avoid touching the electrodes! Place the special
abrasive paper on top of a clean paper towel and rub the electrode
tip over the abrasive paper, holding the electrode at a slight angle.
Repeat several times at different angles. Never touch or clean the
brown electrode shaft.
2. Remove the rubber band from the groove in the membrane cap just
until the vent hole underneath is exposed, then fill the membrane
cap to the top with the electrolyte fill solution. Never shake the
electrolyte bottle, it must stay free of bubbles!
3. Hold the sensor body vertically with the tip pointing down and
SLOWLY screw on the membrane cap until it is hand tight. Be
prepared for some electrolyte solution to squeeze out from the
vent hole in the cap.
4. Rinse your hands, the sensor, and all surfaces contaminated with
electrolyte solution with running water. Check the sensor for leaks,
especially at the membrane and the membrane cap threads. If any
leaks are detected, tighten the membrane cap or replace it. Move the
rubber band back into the groove. Never remove the membrane
cap with the rubber band covering the vent hole, or the
membrane will be damaged!
5. Push the cable onto the end of the sensor, aligning the pins with the
holes. Turn the connector until hand tight to seal the cable
connection.

3
Hydrogen Peroxide Sensors
1. The sensor is delivered with the membrane cap loosely screwed on
the electrode shaft. Pull the transparent protection cap off the
membrane cap and unscrew the membrane cap. Place the membrane
cap onto a clean hard surface. Fill the membrane cap up to the edge
with the enclosed electrolyte, empty it out and refill again up to the
edge.
2. Place the G-Holder on a clean hard surface and fill it with electrolyte.
3. Lift up the G-Holder which is moisturized with electrolyte with the
supplied tweezers. Insert the G-holder in the filled membrane cap.
Let it down until the G-holder is held by the indentation in the
middle of the membrane cap. Then remove the tweezers carefully.
The G-holder stays in the membrane cap.
4. Clean just the tip of the working electrode with the special abrasive
paper supplied. Avoid touching the electrodes! Place the special
abrasive paper on top of a clean paper towel and rub the electrode tip
over the abrasive paper, holding the electrode at a slight angle Repeat
several times at different angles. Never touch or clean the brown
electrode shaft.
5. Holding the electrode shaft upright, place it onto the filled membrane
cap with the mounted G-holder. You may have to turn it counter-
clockwise first until the thread catches. Then screw the electrode
shaft (manually) slowly clockwise into the membrane cap. Be
prepared for some electrolyte solution to squeeze out from the
vent hole in the cap.
6. Make sure the red o-ring is in its proper position as it is the seal of
the membrane cap. Screw the membrane cap (manually) tightly to
the electrode shaft. The red o-ring will be firmly squeezed between
the two parts. The membrane is deflected to the outside by the
electrode probe.
7. Rinse your hands, the sensor, and all surfaces contaminated with
electrolyte solution with running water. Check the sensor for leaks,
especially at the membrane and the membrane cap threads. If any
leaks are detected, tighten the membrane cap or replace it.
8. Once the membrane cap is assembled, take care not to touch the
membrane with your hand or any other object!
9. Push the cable onto the end of the sensor, aligning the pins with the
holes. Turn the connector until hand tight to seal the cable
connection.

4
Other Sensors
1. Remove the black protective tube from the electrode tip, and clean
just the tip of the working electrode with the special abrasive paper
supplied. Avoid touching the electrodes! Place the special abrasive
paper on top of a clean paper towel and rub the electrode tip over
the abrasive paper, holding the electrode at a slight angle Repeat
several times at different angles. Never touch or clean the brown
electrode shaft.
2. Open the vial containing the membrane cap. Empty out the water.
Make sure that only one grey rubber band is in the groove covering
the vent hole in the membrane cap. Fill the membrane cap to the
top with the electrolyte fill solution.
3. Hold the sensor body vertically with the tip pointing down and
SLOWLY screw on the membrane cap until it is hand tight. Be
prepared for some electrolyte solution to squeeze out from the
vent hole in the cap.
4. Push the second grey band into the groove in the cap, making sure
that the bands are smooth and flush.
5. Rinse your hands, the sensor, and all surfaces contaminated with
electrolyte solution with running water. Check the sensor for leaks,
especially at the membrane and the membrane cap threads. If any
leaks are detected, tighten the membrane cap or replace it.
6. Push the cable onto the end of the sensor, aligning the pins with the
holes. Turn the connector until hand tight to seal the cable
connection.
Flow Cell Placement
Instructions for mounting the sensor into the process can vary greatly with
the circumstances that are encountered in your application. Here are some
general guidelines to assist you. Refer also to the typical installation
drawings.
The sensor should be mounted such that the measuring surfaces will
always stay wet. If the membrane dries out, it will respond slowly to
changing disinfectant values for 24 hours, and if dried out repeatedly, will
fail prematurely. If the sensor is left dry for longer than 24 hours, the
membrane cap must be replaced!
The flow cell should be placed on the discharge side of a circulation pump
or downhill from a gravity feed. Flow into the cell must come from the

5
bottom side that has the ¾” x ¼” NPT reducing bushing installed. The
reducing bushing provides the flow velocity required for accurate
readings and must not be removed!
A “U” trap should be installed so that if the flow stops, the sensor is still
immersed in the water. The outlet of the flow cell must be plumbed to open
atmosphere unless the system pressure is at or below 1 atmosphere. If the
flow through the line cannot be stopped to allow for cleaning and
calibration of the sensor, then it should be placed in a by-pass line with
isolation valves to allow for sensor removal. Install the sensor vertically,
with the measuring surface pointing down, at least 5 degrees above
horizontal. (Refer to Installation drawings)
Flow rate regulation must be done upstream from the sensor, because any
flow restriction downstream can increase the pressure above atmospheric
and damage the membrane cap!
The sensor should be installed in an area where there is good solution
movement and where it will respond rapidly to chemical additions. The
placement of the sensor relative to the placement of chemical
replenishment, along with the quality of the mixing, and the replenishment
chemical flow rate are critical to accurate process control.
To avoid biological growth on the membrane, which can block
measurement, never leave the sensor in water without oxidant for longer
than 24 hours.
Installing Sensor into Flow Cell
1. Assemble the flow cell as shown below from the top down. The reducer
should already be installed in the flow cell body.
2. Slide the 103419-B bottom washer (concave side up) over the cable end
of the sensor, followed by the 103422 O-ring, followed by the 103419-T
top washer (concave side down), followed by the 102586 nut.
3. Place the 102594 O-ring in the top o-ring groove of the 191279-R flow
cell body.
4. Place the sensor body into the flow cell body, and tighten the 102586 nut
until it is hand-tight. Before tightening completely, pull the sensor up
until the clip ring is up against the bottom washer.

6
Sensor Parts Exploded View
Disinfection
Sensor
Washer
Set
p/n 103419
O-Ring
p/n 103422
Nut, p/n 102586
Cable, p/n 191303 (for WDIS400 & WebMaster)
Cable, p/n 191655 (for W100 & W600)
Membrane cap
Clip Ring groove
Clip ring
O-Ring
p/n 102594
Body, p/n 191279-R

7
Typical Installation
ISOLATION
VALVE
(NORMALLY
OPEN)
RECIRCULATION
PUMP
ROTAMETER
30-100 LPH
PROCESS WATER
SAMPLE RETURN
1 ATMOSPHERE MAXIMUM
FLOW
SWITCH
SENSOR
FLOW CELL
FLOW
CONTROL
VALVE
SAMPLE
VALVE

8
Wiring Instructions
WebMaster
The sensor is provided with a 2-twisted pair, shielded, 24 AWG, 35
pF/foot capacitance cable. The wiring to the controller is as follows:
Shield Drain: Earth Ground
GRN: IN+
WHT: IN-
RED: +5 V
BLK: - 5 V
If the required cable length exceeds the 6 meters (20 feet) that is supplied,
wire the housing to a 190851 terminal box, then use a p/n 100084 cable to
reach the instrument. The maximum cable length is 30.5 meters (100 feet).

9
WDIS410 or WDS100 or WDS600 or W900
The sensor is provided with a 2-twisted pair, shielded, 24 AWG, 35 pF/foot
capacitance cable. The wiring to the controller is as follows:
Shield Drain: Earth Ground
GRN: IN+
WHT: IN-
RED: +5 V
BLK: - 5 V
If the required cable length exceeds the 6 meters (20 feet) that is supplied,
wire the housing to a 190851 terminal box, then use a p/n 100084 cable to
reach the instrument. The maximum cable length is 30.5 meters (100 feet).
WDIS410
Power Supply
(115 VAC or 230 VAC)
Contact Closure:
Polarity not critical
Interlock Function
+5V
T-T+
GROUND
STUD
L1 L2/N
GRN120V
GRN/YEL240V
WHT 120V
BLU 240V
BLK120V
BRN240V
IN+ IN- +5V -5V
-5VIN+ IN-
IN-
DIG IN 2 DIG IN 3
IN+ IN-
DIG IN 1 IN+
IN-
IN+ DIG IN 4 IN+ IN- DIG IN 5 IN+ IN-
IN-
DIG IN 2 DIG IN 3
IN+ IN-
DIG IN 1 IN+
IN-
IN+ DIG IN 4
IN+ IN- DIG IN 5
IN+ IN-
L1 L2/N
L2 L2 L2 L2 L2 L2 BLEED
N.C. N.O. N.C.
BOI 1
N.O.N.C.
FEED
N.C.
BIO 2
N.O. N.C. N.O. N.O.
ALARM
N.C. N.O.
GREEN
WHITE
RED
BLACK
Disinfection
Sensor

10
WDS600
TB1 or 2
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
TB3 TB2
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
TB1 TB4 TB6
TB5
TB7
N
N
N
N
N
N
R1
R2
R3
R4
R5
R6
POWER
SWITCH FUSE
IN– WHT
IN+ GRN
+5V RED
-5V BLK
SENSOR LABEL
SHIELD
1
2
3
4
5
6
7
8
9

11
WDSW100
1
2
3
4
5
6
7
8
9
10
11
12
TB2
TB1 FUSE POWER
SWITCH
POWER
SWITCH
1
2
3
4
5
6
7
8
9
10
11
12
R1
R2
R3
N
N
N
N
L
TB3
TB4
TB5
TB6
TB7 +
pH
–
TB1
1
2
3
4
5
6
7
8
9
10
11
12
-5V BLK
IN– WH T
IN+ GRN
SHIELD
+5V RED
SAFETY COVER LABEL

12
W900

13
3.0 Operation
This section describes how to prepare the sensor for use.
Conditioning
The sensor requires conditioning to acclimate the electrodes prior to
generating stable readings. Conditioning consists of installing the sensor
in the flow cell, ensuring that the sensor remains wet at all times with
water containing the disinfectant to be measured, and supplying power
to the sensor.
The following conditioning times are recommended:
New Sensor 12 –24 hours
After membrane
or electrolyte replacement 1-3 hours (see specifications in section 6.0)
Calibration
The frequency of calibration is a function of many factors. These factors
include:
1. The accuracy required by the application.
2. The value of the off-specification product versus the cost of
calibration.
3. The coating or abrasive nature of the application.
4. The stability of the sensor and controller as a system.
The frequency of calibration is really determined by experience. At a
new installation, calibration might initially be checked every day by
comparing the controller reading to a DPD test or other manual analysis
and logging the results. If the reading drifts off significantly in one
direction you should consider calibrating. Resist the temptation to
calibrate to correct for small errors that may be a result of normal
variations in the test methods.
A calibration MUST be performed on initial installation, or after
cleaning or replacing the membrane or electrolyte. A sensor installed in
clean water can hold its calibration for several months.
DO NOT attempt to perform a calibration until the following conditions
have been met:
1.The sensor has been conditioned as described above.
2.The sensor has equilibrated to the temperature of the water (for the
zero calibration) or the sample (for the 1 point process calibration).

14

15
Zero Calibration
1. Remove the sensor from the flow cell and place it in a beaker of clean,
oxidizer-free water.
2. Allow the sensor 15 minutes to equilibrate to the water temperature.
3. Go to the Zero Calibration menu of the controller. Refer to the controller
instructions.
4. Stir the water with the sensor until the mV reading is stable for at least 5
minutes.
5. When the reading is stable, continue to the final steps of the calibration.
6. Return the sensor to the flow cell and check for leaks.
One Point Process Calibration
1. Ensure that the sensor is conditioned and equilibrated to the temperature
of the sample.
2. Ensure that the sample flow rate is between 30 and 100 liters/hour.
3. Perform a DPD test or other manual analysis on the sample water.
4. Go to the One Point Process Calibration menu of the controller. Refer to
the controller instructions.
5. When the reading is stable, continue to the final steps of the calibration.
NOTE: Disinfectant concentration can change rapidly in the sample!
Minimize the time between performing the DPD test or manual analysis and
finishing the calibration!
4.0 Troubleshooting
The disinfectant reading is much lower than the manual
analysis
Possible Causes
Corrective Actions
Insufficient conditioning
Wait for the appropriate amount of time
before attempting a calibration.
Insufficient sample flow
Increase flow rate to between 30 and 100 liter
per hour.
Air bubbles on membrane
Dislodge bubbles. Adjust flow rate higher if
necessary.
Dirty membrane
Clean membrane
Loose membrane cap
Tighten membrane cap.
Faulty membrane
Replace membrane cap.
High Pressure
Reduce pressure to below 1 atmosphere and
refill cap with electrolyte
No electrolyte fill solution in
membrane cap
Fill membrane cap with electrolyte. Replace
membrane cap if it will not hold solution.
Faulty sensor
Replace sensor
Faulty analysis equipment or
reagents
Consult test equipment instructions

16
The disinfectant reading is much higher than the manual
analysis
Possible Causes
Corrective Actions
Insufficient conditioning
Wait for the appropriate amount of time
before attempting a calibration.
Faulty membrane
Replace membrane cap.
Faulty sensor
Replace sensor
Faulty analysis equipment or
reagents
Consult test equipment instructions
Sample contaminated with
interfering molecule (refer to
Sensitivity specification in
Section 6)
Remove source of contamination
Sensor Error
This error message appears if the signal from the sensor is outside the range
of –1400 to 1400 mVDC (WebMaster) or –2000 to 2000 (WDIS) or -2560
to 60 mV (W100/W600/900)
Possible Causes
Corrective Actions
Faulty wiring
Check wiring
Faulty sensor
Replace sensor
Faulty controller sensor input
Go to the Sensor Input menu and perform a self
test. If this passes, then the problem is with the
sensor or its wiring. If it fails, then disconnect
the sensor from the circuit board and try the
self test again. If it still fails, replace the circuit
board.
Disinfectant Reading is Unstable
Possible Causes
Corrective Actions
Air bubbles on membrane
Dislodge bubbles. Adjust flow rate higher if
necessary.
Air bubbles in electrolyte
Refill membrane cap with electrolyte.
Faulty membrane
Replace membrane cap.
Faulty wiring
Check wiring
Faulty controller sensor input
Go to the Sensor Input menu and perform a self
test. If this passes, then the problem is with the
sensor or its wiring. If it fails, then disconnect
the sensor from the circuit board and try the
self test again. If it still fails, replace the circuit
board.

17
Calibration Failure
For WebMaster
The controller will display a calibration failure if the offset calculated in the
Zero Calibration is outside of the range –20 to 40 mV or the slope
(mV/ppm) calculated in the One Point Process Calibration is outside of the
range of the nominal mV per 0.1 to 2.0 ppm.
For WDIS:
The acceptable range for the slope (mV/ppm) is the nominal mV per 0.5 to
2.0 ppm. The range of mV for a Zero Calibration is –100 mV to 100 mV.
For W100 or W600 or 900:
The calibration will fail if the adjustment to the gain is outside of 0.2 to
10.0, or if the calculated offset is outside of -40 to 40 mV.
To calculate the nominal slope for your sensor, divide the high end of the
nominal range by -2000. For example, for a 0-20 ppm sensor, the nominal
slope is -2000/20 = -100 mV/ppm.
Possible Causes
Corrective Actions
Insufficient conditioning
Wait for the appropriate amount of time
before attempting a calibration.
Insufficient sample flow
Increase flow rate to between 30 and 100
liters per hour
Air bubbles on membrane
Dislodge bubbles. Adjust flow rate higher
if necessary.
Dirty membrane
Clean membrane
Faulty membrane
Replace membrane cap.
High Pressure
Reduce pressure to below 1 atmosphere and
refill cap with electrolyte
No electrolyte fill solution in
membrane cap
Fill membrane cap with electrolyte.
Replace membrane cap if it will not hold
solution.
Faulty sensor
Replace sensor
Faulty analysis equipment or
reagents
Consult test equipment instructions
Sample contaminated with
interfering molecule (refer to
Sensitivity specification in
section 6.0)
Remove source of contamination
Faulty wiring
Check wiring
Faulty controller sensor input
Go to the Sensor Input Page and perform a
self test. If this passes, then the problem is
with the sensor or its wiring. If it fails, then
disconnect the sensor from the circuit board
and try the self test again. If it still fails,
replace the circuit board.