Xylem WQL User Manual

SensoLyt® WQL

pH electrode with polymer electrolyte

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Operating manual

7

SensoLyt®WQL

Note

The latest version of the present operating manual can be found on the
Internet under www.WTW.com.

Copyright © Weilheim 2009, WTW GmbH

Reprinting - even as excerpts - is only allowed with the explicit written
authorization of WTW GmbH, Weilheim.
Printed in Germany.

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SensoLyt®WQL Technical data

Technical data

General data Reference electrolyte Polymer electrolyte, AgCl-free

Junction Single hole junction
Shunt element Ag/AgCl
NTC Yes

Measurement and

application

characteristics

Dimensions,

weight

Materials Shaft Glass

pH measuring range 2.000 ... 12.000
Allowed temperature range 0 ... 60 °C (32 ... 140 ° F)
Membrane resistance at

< 500 MOhm

25 °C
Pressure resistance* IP 68 (10

6

Pa or 10 bar)

Typical application Use in WQL-pH logger

* The electrodes meet the requirements according to article 3(3) of the
directive, 97/23/EC ("pressure equipment directive").

Shaft length 120 mm
Shaft diameter 12 mm
Weight approx. 45 g

Connecting head 12 mm
SMEK plug PEEK with gold-plated contacts
O-rings FPM (Viton)

Electrical

connection

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SMEK head, 6-pole

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Commissioning, measuring, calibration SensoLyt®WQL

Junction

Commissioning, measuring, calibration

Commissioning Prepare the combination electrode for measuring as follows:

z Remove the watering cap from the electrode tip. Possible salt deposits in

the area of the watering cap do not affect the measuring characteristics
and can easily be removed with deionized water.

Note

Please keep the watering cap. It is required for the electrode to be stored.
Always keep the watering cap clean.

z Install the electrode in the logger (see operating manual of the logger).
z Calibrate the electrode according to the operating manual of the logger

and observe the following rules while doing so:

Calibration

and measurement:

General rules

z Avoid the carryover of any solution (sample or buffer solution) from one

measurement to the next by taking the following measures:
– Shortly rinse the calibration and sample beakers with the solution the

beakers are to be filled with next.

– Between measurements, rinse the electrode with the solution that fol-

lows. Alternatively, you can also rinse the electrode with deionized wa­ter and then carefully dab it dry.

z To measure in aqueous solutions, it is recommended to immerse the elec-

trode in a vertical or slightly tilted position.

z Observe the correct depth of immersion and make sure the contact be-

tween the junction and test sample is thorough. The junction (hole junc­tion) is in the area of the bottom end of the shaft.

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Subsequent

calibrations

z For measurements in aqueous solutions, provide approximately the same

stirring conditions for measuring as for calibrating.

Note

Keep the protective head mounted to the logger during calibration and
measurement in order avoid damage to the pH membrane.

The frequency of subsequent calibrations depends on the application.

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SensoLyt®WQL Aging

Storage

During short

measuring breaks

Overnight or

longer

Immerse the electrode in reference electrolyte (KCl 3 mol/L, Ag+ free). Prior
to the next measurement, shortly rinse the electrode with the test sample or
deionized water.

For prolonged storage we recommend to keep the electrode installed in the
logger. Put the clean electrode in the watering cap that is filled with reference
electrolyte (KCl 3 mol/L, Ag
logger for more information.

Note

pH electrodes must not be stored dry or in deionized water. The electrode
could be permanently damaged by this. If the liquid in the watering cap has
dried up, condition the electrode in reference electrolyte (KCl 3 mol/L, Ag+
free) for at least 24 hours.

Note

During longer storing periods, salt sediments may develop on the watering
cap. They do not affect the measuring characteristics and can easily be re­moved with deionized water when the electrode is put into operation again.

+

free). Refer to the operating manual of the

Aging

+

Every pH electrode undergoes a natural aging process. With aging, the re­sponding behavior becomes slower and the electrode slope and asymmetry
change. Moreover, extreme operating conditions can considerably shorten
the lifetime of the electrode. These are:

z Strong acids or lyes, hydrofluoric acid, organic solvents, oils, fats, bro-

mides, sulfides, iodides, proteins

z High temperatures
z High changes in pH and temperature.
z Media with very low electrical conductivity

The warranty does not cover failure caused by measuring conditions and
mechanical damage.

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Maintenance and cleaning SensoLyt®WQL

Maintenance and cleaning

Cleaning Remove water-soluble contamination by rinsing with deionized water. Other

types of contamination have to be removed as follows while the contact time
with the detergents should be kept as short as possible:

Contamination Cleaning procedure

Fat and oil Rinse with water containing household wash-

ing-up liquid

Lime and hydroxide deposits Rinse with citric acid (10 % by weight)

Note

Hydrofluoric acid, hot phosphoric acid and strong alkaline solutions destroy
the glass membrane.

After cleaning Rinse the electrode with deionized water and condition it in reference

electrolyte solution for at least 1 hour. Then recalibrate the electrode.

Wear parts and accessories

Description Model Order no.

Reference electrolyte solution 250 ml
to fill the watering cap
(KCl 3 mol/l, Ag

Note

Detailed information on our wide range of buffer solutions and more acces­sories is given in the price list of the WTW catalog "Laboratory and field in­strumentation".

+

-free)

KCl-250 109 705

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Wissenschaftlich-Technische Werkstätten GmbH

Dr.-Karl-Slevogt-Straße 1
D-82362 Weilheim

Germany

Tel: [phone]

[phone]
Fax: [phone]
E-Mail: [e-mail]
Internet: http://www.WTW.com