Omega Products CLDTX-100 User Manual

CLDTX-100 Series

SECTION 1.0

THEORY OF OPERATION

1.0 CHLORINE DIOXIDE INTRODUCTION. Chlorine dioxide is
considered one of the most powerful biocides available today.
It is so effective that it was used to disinfect sites infected
with the SARS virus and is used to disinfect areas know to be
contaminate with Legionella sp. One of the most important
properties of ClO2 that sets it apart from chlorine is its be­havior when placed in water. Not only is ClO2 10 times more
soluble in water than chlorine (3.01 grams/Liter at 25 degrees
C), it doesn't hydrolyze when placed in solution. It remains as
a "true" dissolved gas that retains its useful oxidative and bio­cidal properties throughout the entire 2 to 10 pH range.

1.2 SENSOR OPERATING PRINCIPLE. Chlorine dioxide gas
diffuses across the sensor's hydrophobic silicone membrane
between the cathode and electrolyte solution. At the applied
potential, it is electrochemically reduced at the gold cathode
as:
ClO2 + 4H+ + 5e- ---> Cl- + 2 H2O
At the same time, the silver anode is oxidized to form silver
chloride (AgCl) as:
Cl- + Ag ---> AgCl + e-
The release of electrons at the cathode and acceptance at the
anode creates a current flow, which under constant conditions,
is proportional to the chlorine dioxide concentration in the
medium outside the sensor. The resulting low current output
is then conditioned to 4-20mA current by the sensor's on­board electronic circuitry.

PRODUCT INSTRUCTION SHEET

SECTION 2.0

FACTORS INFLUENCING THE SENSOR

2.1 pH. As dicussed in Section 1, there is no significant pH
dependence when measuring ClO2.

2.2 Chemical Interferences. The sensor should not be used in
water containing surfactants.

2.3 FLOW. The membrance covered chlorine dioxide sensors
(CLD series) function at any flow rate. To acheive reproduc­ible measurements, these sensors require a specified constant
flow rate. To avoid complications (such as bubbles), it is best to
operate the sensors at a flow rate of 0.2-0.6 gpm.

Parts covered by this product instruction sheet include: CLDTX-100 Series

M4678/0708 page 1 of 6

PRODUCT INSTRUCTION SHEET

SECTION 3.0

SENSOR PREPARATION

3.0 CHLORINE DIOXIDE SENSOR ASSEMBLY. Your Chlorine Di­oxide sensor is shipped with the membrane cap (CLDA-2016)
pre-installed and covered with a cap with water inside to keep
the membrane wet.
NOTE: IF SENSOR WILL BE STORED DRY OUT OF FLOW CELL,
SHAKE BODY DOWNWARD INTO A SINK TO REMOVE THE FILL
SOLUTION. TAKE THE MEMBRANE CAP AND IMMERSE IN A
CUP OF TAP WATER UNTILL READY TO REUSE. SEE SECTION 9.
REPLACE CAP AND ELECTROLYTE BEFORE INSTALLING INTO
FLOW CELL (see SECTION 10 for cap and electrolyte change.
See SECTION 5 for sensor installation into flow cell).

SECTION 4.0

FLOW CELL INSTALLATION

4.0 FLOW CELL. To obtain accurate Chlorine dioxide reading,
the Sensor must be installed into the Flow Cell to prevent air
bubbles formation on the membrane, proper spacing between
the sensor and the installation wall, and laminar flow across
the membrane.

4.1. Using two 1/4” NPT Tube fittings, connect the Flow Cell
into your system, noting the inlet (bottom) and outlet (side)
orientation. (see FIGURE 1)

4.2. Install clamp with rubber backing as shown in FIG. 2.

4.3 Drill 3/8" diameter hole on the panel.

4.4 Insert bolt as shown in FIG 2

4.5 On back of panel attach lock washer and nut to secure
clamp and flow cell to panel.

FIG.1

SENSOR

SNAP RING

GROOVE

THREADED FITTING

SNAP RING (INSTAL L S
INTO PROBE GROOVE)

O-RING

BARBED TUBE
FITTING

FLOW CELL

BARBED TUBE
FITTING

FIG. 2

SECTION 5.0

SENSOR INSTALLATION

5.0 SENSOR INSTALLATION INTO FLOW CELL.
a. First install threaded fitting onto sensor body
(remove fitting if pre-installed in flow cell)
b. Install snap-ring into groove on sensor body
c. Next, slide o-ring onto body of sensor until it
reaches bottom of threaded fitting.
d. Thread sensor assembly into top of flow cell as
shown in FIGURE 2.
d. Turn on flow and verify the flow through the Flow
Cell is at least 0.2gpm (45 liters/hour and no
more than 0.6gpm (135 liters/hour).

Parts covered by this product instruction sheet include: CLDTX-100 Series

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PRODUCT INSTRUCTION SHEET

SECTION 6.0

ELECTRICAL INSTALLATION

6.0 ELECTRICAL INSTALLATION. The sensor produces an ap­proximate output of 4 mA in air and 20mA at the top range of
chlorine dioxide output (0-1ppm, 0-2ppm, 0-5ppm).

NOTE: The supply voltage to the Sensor must be 12-24 V DC with
minimum of 250 mA. Maximum load is 1 Watt. The sensor has 3 wires,
red (+) , black (-) and clear (shield). Twist together or solder black
and clear if instrument does not have separate ground. If a separate
ground is available such as for PLC’s connect clear (shield) to it.
Attach the red wire to the power supply positive terminal (+)and the
black wire to the PLC or DVM positive (+) terminal. Connect a wire
(customer supplied) from the power suppy negative (-) and the PLC or
DVM (-). See FIG 3. The Sensor will require several minutes to stabilize

after power is supplied to it.

SECTION 7.0

SENSOR CONDITIONING

7.0 SENSOR CONDITIONING The sensor requires conditioning
prior to generating stable values.
a. For new Sensors, allow the Sensor to run for at least
hours before calibration.
b. If the Sensor will be un-powered for 2 hours or
more, run for 3 hours prior to use.
c. After membrane/electrolyte replacement, allow the
Sensor to run for at least 4 hours.

FIG. 3

Power Supply

sensor red wire

sensor
black wire

PLC, DVM,...

Parts covered by this product instruction sheet include: CLDTX-100 Series

M4678/0708 page 3 of 6

PRODUCT INSTRUCTION SHEET

SECTION 8.0

CALIBRATION

IMPORTANT NOTE: SENSORS ARE SUPPLIED FACTORY CALIBRATED WITH A
4-20mA SIGNAL OUTPUT CORRESPONDING TO THEIR SPECIFIC RANGE (0-1,
0-2 OR 0-5ppm ClO2). SPAN CALIBRATION IS NECESSARY WHEN RECEIVING
A NEW SENSOR SINCE YOUR CONDITIONS MAY VARY FROM THOSE USED AT
THE FACTORY FOR SPAN CALIBRATION. THE ZERO POINT CALIBRATION IS
NOT NECESSARY SINCE THE ZERO SETTING IS VERY STABLE.

PERIODIC CALIBRATION ( ABOUT ONCE PER WEEK) IS RECOMMENDED. THIS
USEFUL IN TRACKING SENSOR FAILURES AS WELL.

8.1 Removal of cord grip to access ZERO and SPAN
potentiometers inside the sensor body:
a. Remove top nut of cord grip as shown in FIGURE 4.
b. Remove remaining cord grip as shown in FIGURE 5. A wrench
may be required.

8.2 Slope Calibration:
a. Determine the chlorine dioxide (ClO2) concentration using a
diethyl-p-phenylenediamine (DPD) colorimeter test kit
(see FIGURE 9.), not included with ClO2 sensor and flow cell.
b. Measure Chlorine dioxide content with sensor. Make sure that
calibration flow rate matches flow rate when
measuring sample since probe output is flow rate dependent.
c. Adjust the span potentiometer to the desired mA (see
FIGURES 9 & 9A)
c. Repeat this slope calibration one day after sensor is
initially installed.
d. Routinely repeat the slope calibration monthly.

FIG. 4

FIG. 6

FIG. 5

FIG. 7

Left
potentiometer
(Zero adjust)

Right
potentiometer
(Span adjust)

Cable

SECTION 9.0

SENSOR STORAGE

9.0 STORAGE. Store sensor at 5o C- 50o C ONLY. and maximum
humidity of 95% non-condensing.
a. Short Term Storage (1 week or less): Store in Flow cell
with water to prevent the probe from drying out.
b. Intermediate Term (1 week to 1 month): Store in cap,
bottle, or beaker with water to keep membrane wet.
c. Long Term (1 month or longer): Remove Membrane
Cap and store completely immersed in tap water. Turn
sensor upright and shake it to remove fill solution from
inside the sensor.

FIG. 9

FIG. 8

to Increase

output

to Decrease
output

C

2

L

O

ClO2

ZERO

READ

Note: The DPD method
for chlorine dioxide
(ClO2) measurement is
not selective for ClO2
alone. Other oxidants
in the water can also be
measured as ClO2.

Parts covered by this product instruction sheet include: CLDTX-100 Series

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PRODUCT INSTRUCTION SHEET

SECTION 10.0

SENSOR MAINTENANCE/

RECONDITIONING

10.1 MEMBRANE CAP REPLACEMENT. If membrane replace­ment is required, a new cap with preinstalled membrane must
be used. Order CLD-2016(see Section 12) Cap/membrane
replacement.
To change membrane cap:
a) turn sensor upside down with cap facing upward
b) rotate cap counter-clockwise to remove (see FIG 10).
c) fill sensor body with electrolyte using needle and bottle of
refill solution (see FIG. 11)
d) install new membrane cap by threading cap onto sensor
rotating cap clockwise (opposite of FIG 10)

SECTION 11.0

SENSOR TROUBLESHOOTING

11.1 CALIBRATION PROBLEMS
a) Sensor output HIGHER than DPD test

1) Run in time too short

2) Membrane cap damaged

3) Interference from water
contaminants (see Specifications,
"Cross Sensitivity")

4) Cable short circuit or damage

b) Sensor output LOW ER than DPD test

1) Run in time too short

2) Deposits on Membrane cap

3) Flow rate too low

4) Air bubbles on membrane

5) Surfactants in water

6) No electrolyte in membrane cap

c) Sensor ouput is 4mA (zero ppm)

1) Run in time too short

2) Chlorine dioxide content below
detection limit

3) Sensor not wired correctly (See
SECTION 6.0 of this manual)

4) Defective sensor

d) Sensor output UNSTABLE

1) Air bubbles on membrane

2) Membrane damage

3) Non-sensor problem

FIG. 10

FIG. 11

INJECT UNTIL SOLUTION

LEAKS OUT OF FILL HOLE

TROUBLESHOOTING CHART

Symptom Possible Cause Solution/Remedy

The sensor 1) Run in time too short 1) See Sec 5.0 -CONDITIONING
cannot be 2) Membrane cap damaged 2) Replace cap - See Sec 8.0
calibrated- 3) Interference from contaminants 3) See SPECIFICATIONS
ouput is 4) DPD chemicals bad 4) Use new DPD kit
HIGHER than 5)Temperatue increased since cal 5) Match calibration temp.
DPD Test

The sensor 1) Run in time too short 1) See Sec 7.0 -CONDITIONING
cannot be 2) Deposits on membrane cap 2) Remove deposits or replace
calibrated- cap if cleaning ineffective.
output is 3) Flow rate too low 3) increase fl ow - See
LOWER than SPECIFICATIONS
DPD Test 4) Air bubbles on membrane 4) Remove and re-install sen
sor to remove bubbles.

5) Surfactants in water 5) Remove surfactants and
replace cap

6) No electrolyte in cap 6) Add new electrolyte, run in
sensor and re-calibrate

7) Temperature decreased since cal 7) Increase temp to match cal

8) Organic chlorination agents 8) Use chlorinating agents
present in water per DIN 19643

Sensor output 1) No ClO2 present` 1) Check for ClO2 with
is 4mA (0 ppm) appropriate DPD test.

2) Run in time too short 2) See Sec 7.0 -CONDITIONING

3) ClO2 content below limit 3) Add ClO2, check genera­ tor and repeat calibration

4) No electrolyte in cap 4) Refi ll electrolyte

5) Sensor electrical connection 5) See SECTION 6.0
wrong

Unstable output 1) Air bubbles on sensor membrane 1) Tap to remove bubbles
from sensor 2) Membrane damaged 2) Replace membrane, run in
sensor and recalibrate.

3) Non-sensor problem 3) check PLC or I/O device

Parts covered by this product instruction sheet include: CLDTX-100 Series

M4678/0708 page 5 of 6

PRODUCT INSTRUCTION SHEET

SECTION 12.0

SENSOR SPECIFICATION

12.1 OPERATING SPECIFICATIONS. Follow all operating specifications,
especially for pH and flow rate as noted in the specification tables
below.

TECHNICAL SPECIFICATIONS

SENSOR
Dimensions: 8.2"L x 1" dia
Body Material: Black PVC
Membrane Material: Silicone
O-ring material: Viton
Cathode: Gold
Anode: Silver chloride (AgCl)
Cable: 2 -conductor shielded, 10ft (3mtr)
tinned wire leads
FLOW CELL
Dimensions: 5.58"H x 2.25"DIA
Material: Acrylic
Connections: 1/4" NPT inlet and outlet

OPERATING SPECIFICATIONS

Operating temperature range: 0-45 degC
Maximum operating pressure: 1 bar/14.5 psi/1atm
Flow rate minimum: .20 gpm
Flow rate maximum: 0.6 ppm
pH range: 4-11
Output signal: 4.0+/- 0.2mA in air (zero)
20mA +/- 0.2mA at high range
(2, 5 or 10ppm)
Power Requirement: 12-24 VDC, 250 mA minimum
Cross-Sensitivity:

Do not operate the Sensor in surfactant water. Surfactant water will reduce
life of Sensor.

R

FC72 FLOW CELL DIMENSIONS

SENSOR AND FLOW CELL INSTALLATION DIMENSIONS

MAINTENANCE/REPLACEMENT PARTS

FC72 Flow Cell, 1/4 inch FNPT inlet and outlet, includes:
2 each 1/4" barbed tube fittings, clamp, threaded flow
cell installation fitting

CLD-ES Chlorine dioxide sensor fill solution, 30mL, 1 each

CLD-RM CLD sensor replacement premembraned cap, 1 each

Parts covered by this product instruction sheet include: CLDTX-100 Series

M4678/0708 page 6 of 6