wtw inoLab pH 720 User manual

Accuracy when
going to press
The use of advanced technology and the high quality stan-
dard of our instruments are the result of continuous develop-
ment. This may result in differences between this operating
manual and your instrument.
We cannot guarantee that there are absolutely no errors in
this manual. We are sure you will understand that we cannot
accept any legal claims resulting from the data, figures or
descriptions.
Warranty
declaration
The designated instrument is covered by a warranty of three
years from the date of purchase.
The instrument warranty extends to manufacturing faults
that are determined within the period of warranty.
The warranty excludes components that are replaced during
maintenance such as batteries, etc.
The warranty claim extends to restoring the instrument to
readiness for use but not, however, to any further claim for
damages. Improper handling or unauthorized opening of the
instrument invalidates any warranty claim.
To ascertain the warranty liability, return the instrument and
proof of purchase together with the date of purchase freight
paid or prepaid.
Copyright ©Weilheim 2004, WTW GmbH
Reprinting - even as excerpts - is only allowed with the ex-
plicit written authorization of WTW GmbH, Weilheim.
Printed in Germany.

pH 720 Contents
3
1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1 Keyboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2 Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3 Sockets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1 Authorized use . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2 General safety instructions. . . . . . . . . . . . . . . . 10
3 Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1 Scope of delivery . . . . . . . . . . . . . . . . . . . . . . . 13
3.2 Initial commissioning . . . . . . . . . . . . . . . . . . . . 13
4 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.1 Switch on the instrument . . . . . . . . . . . . . . . . . 15
4.2 Measuring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.2.1 Measuring the pH value . . . . . . . . . . . . 17
4.2.2 Measuring the Redox voltage . . . . . . . . 18
4.3 Calibrating . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.3.1 AutoCal TEC . . . . . . . . . . . . . . . . . . . . . 21
4.3.2 AutoCal DIN . . . . . . . . . . . . . . . . . . . . . 24
4.3.3 ConCal . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.4 Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
5 Maintenance, cleaning, disposal . . . . . . . . . . . 31
5.1 Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.2 Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.3 Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
6 What to do if... . . . . . . . . . . . . . . . . . . . . . . . . . . 33
7 Technical Data. . . . . . . . . . . . . . . . . . . . . . . . . . 37
8 Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Contents pH 720
4

pH 720 Overview
5
1 Overview
The compact inoLab pH 720 precision pH meter lets you
perform pH measurements rapidly and reliably.
The inoLab pH 720 provides the highest degree of operating
comfort, reliability and measuring safety for all applications.
The proven MultiCal®calibration procedures and special
AutoRead function support your work with the pH meter.
Note
The measuring instrument can also be delivered as part of
a set.
Information on this and other accessories is available in the
WTW catalog LABORATORY AND FIELD INSTRUMENTATION or
via the Internet.
1Keypad
2Display
3Sockets
pH
720
3
2
1

Overview pH 720
6
1.1 Keyboard
1Activate/deactivate AutoRead function
2Call up calibration procedure
3Select measuring mode
4Measuring instrument ON/OFF
5Reduce values, scroll
6Increase values, scroll
7Confirm inputs, start AutoRead
1
2
3
4
5
6
7

pH 720 Overview
7
1.2 Display
1.3 Sockets
Caution
Only connect probes to the instrument that cannot feed ex-
cessive voltages or currents (> SELV and > circuit with cur-
rent limiter).
Almost all commercial electrodes - especially WTW elec-
trodes - meet these requirements.
Connectors:
1pH electrode
2Temperature probe
3Reference electrode
4Plug-in power supply (option)
Status line
Measured value display
Function and
temperature display
Electrode symbol
1
2
3
4

Overview pH 720
8

pH 720 Safety
9
2 Safety
This operating manual contains basic instructions that you
must follow during the commissioning, operation and main-
tenance of the pH meter. Consequently, all responsible per-
sonnel must read this operating manual before working with
the instrument.
The operating manual must always be available within the
vicinity of the instrument.
Target group This measuring instrument was developed for use in the lab-
oratory.
Thus, we assume that, as a result of their professional train-
ing and experience, the operators will know the necessary
safety precautions to take when handling chemicals.
Symbols used
Caution
indicates instructions that have to be followed to prevent
damage to your instrument.
Warning
indicates instructions that have to be followed to protect
yourself and the instrument from dangerous electrical volt-
age.
Note
Indicates notes that draw your attention to special features.
Note
Indicates cross-references to other documents, e.g. appli-
cation reports, operating manuals of combination elec-
trodes, etc.

Safety pH 720
10
2.1 Authorized use
This instrument is authorized exclusively for pH and Redox
measurements in the laboratory.
The technical specifications as given in chapter 7 TECHNICAL
DATA must be observed. Only the operation and running of
the measuring instrument according to the instructions given
in this operating manual is authorized.
Any other use is considered unauthorized.
2.2 General safety instructions
This instrument is constructed and tested in compliance with
the EN 61010-1 safety regulations for electronic measuring
instruments.
It left the factory in a safe and secure technical condition.
Function and opera-
tional safety
The smooth functioning and operational safety of the instru-
ment can only be guaranteed if the generally applicable
safety measures and the specific safety instructions in this
operating manual are followed.
The smooth functioning and operational safety of the instru-
ment can only be guaranteed under the climatic conditions
specified in chapter 7 TECHNICAL DATA.
If the instrument was transported from a cold environment to
a warm environment, the formation of condensate can lead
to the faulty functioning of the instrument. In this event, wait
until the temperature of the instrument reaches room tem-
perature before putting the instrument back into operation.
Caution
The instrument is only allowed to be opened by personnel
authorized by WTW.

pH 720 Safety
11
Safe operation If safe operation is no longer possible, the instrument must
be taken out of service and secured against inadvertent op-
eration.
Safe operation is no longer possible if:
the instrument has been damaged in transport
the instrument has been stored under adverse conditions
for a lengthy period of time
the instrument is visibly damaged
the instrument no longer operates as described in this
manual.
If you are in doubt contact the supplier of the instrument.
Obligations of the
operator
The operator of this measuring instrument must ensure that
the following laws and guidelines are observed when using
dangerous substances:
EEC directives for protective labor legislation
National protective labor legislation
Safety regulations
Safety datasheets of the chemical manufacturer.

Safety pH 720
12

pH 720 Commissioning
13
3 Commissioning
3.1 Scope of delivery
Laboratory measuring instrument, inoLab pH 720
Operating manual and short manual
4 x type AA Mignon 1.5 V batteries
3.2 Initial commissioning
Perform the following activities:
Set the °C or °F
Set the resolution
Connect the plug-in power supply (optional).
Setting °C or °F The temperature can be displayed in °C or in °F. In the de-
livery condition, the measuring instrument is preset to °C.
To change the unit proceed as follows:
1 Switch the measuring instrument off.
2 Press and hold down the mkey.
3 Press the ekey.
4 Toggle between °C and °F by pressing 28.
5 Confirm with g.
The measuring instrument switches to the measuring
mode.

Commissioning pH 720
14
Connecting the
plug-in power
supply (optional)
The measuring instrument works battery-powered. It can,
however, also be supplied by the plug-in power supply
which is available as an accessory.
Warning
The line voltage on site must lie within the input voltage
range of the original plug-in power supply unit (see chapter
7 TECHNICAL DATA).
Caution
Use original plug-in power supplies only
(see chapter 7 TECHNICAL DATA).
1 Press and hold down the gkey.
2 Press the mkey.
The measured values are displayed with a high reso-
lution, e. g. pH = 4.012.
3 Press the gand keys magain.
The measured values are displayed with a low reso-
lution, e. g. pH = 4.01.
Setting the
resolution
1 Insert the plug (1) into the socket (2) of the pH meter.
2 Connect the original WTW plug-in power supply (3) to
an easily accessible mains socket.
1
2
3

pH 720 Operation
15
4 Operation
4.1 Switch on the instrument
Note
The instrument has an energy saving feature to avoid un-
necessary battery depletion.
The energy saving feature switches the instrument off if no
key has been pressed for an hour.
The energy saving feature is not active if the instrument is
supplied by the plug-in power supply.
1 Place the instrument on a flat surface and protect it
against intense light and heat.
2 Press the ekey.
The Display test appears briefly on the display.
The instrument then switches automatically to the
previously selected measuring mode.
3 Connect the pH electrode to the instrument.
The measuring instrument is ready for operation.

Operation pH 720
16
4.2 Measuring
Preparatory
activities
Perform the following activities when you want to measure:
Note
Incorrect calibration of the pH electrode will result in incor-
rect measured values. Therefore, regularly perform calibra-
tion before measuring.
Temperature probe Measurements can be performed with and without a temper-
ature probe. A connected temperature probe is indicated by
TP on the display.
Note
The pH meter automatically recognizes the type of the tem-
perature probe used. As a result, you can connect elec-
trodes with the NTC30 or Pt1000.
The temperature measurement is absolutely essential for a
reproducible pH measurement. If the measurement is made
without a temperature probe, proceed as follows:
Note
When calibrating without a temperature probe, set up the
current temperature of the respective buffer solution manu-
ally by pressing the 28 keys.
1 Connect the pH electrode to the instrument.
2 Adjust the temperature of the buffer or test solutions
or measure the current temperature if the measure-
ment is made without a temperature probe.
3 Calibrate or check the instrument with the pH elec-
trode.
4 Select the measuring mode by pressing m.
1 Determine the current temperature using a thermo-
meter.
2 Set up the temperature by pressing 28.

pH 720 Operation
17
4.2.1 Measuring the pH value
AutoRead AR
(Drift control)
The AutoRead function (drift control) checks the stability of
the measurement signal. The stability has a considerable ef-
fect on the reproducibility of the measured values.
For identical measurement conditions, the following criteria
apply:
pH value: better than 0.02 (setting time: > 30 s)
1 Perform the preparatory activities according to sec-
tion 4.2.
2 Immerse the pH electrode into the test sample.
3 Press the mkey until pH appears in the status dis-
play. The pH value appears on the display.
1 Call up the pH measuring mode by pressing m.
2 Activate the AutoRead function by pressing a.
The current measured value is frozen (Hold function).
3 Start the AutoRead function by pressing g.
AR flashes on the display until a stable measured val-
ue is reached.
4 If necessary, start the next AutoRead measurement
by pressing g.
5 To terminate the AutoRead function: Press the a
key.

Operation pH 720
18
Note
The current AutoRead measurement (with acceptance of
the current value) can be terminated at any time by pressing
g.
4.2.2 Measuring the Redox voltage
The instrument can measure the Redox voltage (mV) of a
solution when connected with a Redox electrode, e.g.
SenTix ORP.
Note
Redox electrodes are not calibrated. However, you can
check Redox electrodes using a test solution.
1 Perform the preparatory activities according to sec-
tion 4.2.
2 Immerse the Redox electrode into the test sample.
3 Press the mkey repeatedly until U appears in the
status line.
The Redox voltage (mV) of the sample appears on
the display.
4 Wait for a stable measured value.

pH 720 Operation
19
4.3 Calibrating
Why calibrate? pH electrodes age. This changes the asymmetry (zero
point) and slope of the pH electrode. As a result, an inexact
measured value is displayed. Calibration determines the
current values of the asymmetry and slope of the electrode
and they are stored in the instrument.
Thus, you should calibrate at regular intervals.
When to calibrate? After connecting another electrode
When the sensor symbol flashes:
– after expiry of the calibration interval
– after a voltage interruption, e.g. battery change
Calibration points Calibration can be performed using one, two or three buffer
solutions (single point calibration, two-point calibration and
three-point calibration). In three-point calibration, two sepa-
rate asymmetry and slope values (ASY1/S1 and ASY2/S2)
are determined for the two ranges between the three buff-
ers. For measuring, the calibration values relevant for the
respective range are used.
You can choose between 3 calibration procedures:
AutoCal TEC is specially adapted to the WTW technical buffer solutions
as a fully automatic two or three-point calibration. The buffer
solutions are automatically recognized by the instrument.
AutoCal DIN is specially adapted to permanently programmed buffer so-
lutions according to DIN 19266 as a fully automatic two or
three-point calibration. The buffer solutions are automatical-
ly recognized by the instrument.
ConCal is the conventional two-point calibration with 2 freely
selectable buffer solutions or single-point calibration as the
rapid method.
AutoRead In calibration using AutoCal TEC and AutoCal DIN, the Au-
toRead function is automatically activated.
The current AutoRead measurement (with acceptance of
the current value) can be terminated at any time by pressing
g.

Operation pH 720
20
Calibration
evaluation
After the calibration, the instrument automatically evaluates
the current status. The asymmetry and slope are separately
evaluated. The worst evaluation appears on the display.
Display Asymmetry
[mV]
Slope
[mV/pH]
-15 ... +15 -60.5 ... -58
-20 ... +20 -58 ... -57
-25 ... +25 -61 ... -60.5
or
-57 ... -56
Clean the electrode accord-
ing to the sensor operating
manual
-30 ... +30 -62 ... -61
or
-56 ... -50
E3
Clear the fault according to
chapter 6 WHAT TO DO IF...
< -30 or
> 30
< -62 or
> -50
1 Switch on the instrument by pressing e.
2 Connect the pH electrode to the instrument.
3 Keep the buffer solutions ready.
4 Adjust the temperature of the solutions and measure
the current temperature if the measurement is per-
formed without a temperature probe.
Preparatory
activities