VWR DO-230 User manual

Instruction manual
VWR® DISSOLVED OXYGEN METER DO-230
EU Catalogue Number: 664-0236
Version: 1.0
Issued: 1, December, 2020

Legal Address of Manufacturer
VWR International bv
Researchpark Haasrode 2020
Geldenaaksebaan 464
B-3001 Leuven
+ 32 16 385011
www.vwr.com
Country of origin: Poland

CONTENTS
I. Introduction 1
1. Package content 2
2. Exploitation notices 2
3. Characteristics of the meter 2
4. The outside view 3
5. The meter‘s maintenance 5
6. Switching the meter on and off 6
6.1. Stabilised reading 7
7. Preparation to work 8
7.1. Choosing the kind of the temperature compensation 8
II. Oxygen concentration measurement 9
8. Basic information about the oxygen measurement 10
9. Entering the oxygen measurement parameters 12
9.1. Unit 12
9.2. Calibration points and date 12
9.3. Calibration validity time 13
9.4. The salinity influence compensation 13
9.5. Atmospheric pressure influence compensation 15
10. Calibration of the oxygen sensor 16
11. Measurement of oxygen concentration in water 18
11.1. Measurement with automatic temperature compensation 18
11.2. Measurement with manual temperature compensation 19
12. Measurement of oxygen content in air 20
III. Temperature measurement 21
13. Setting the temperature measurement parameters 22
13.1. Unit 22
13.2. Temperature of the manual compensation 22
14. Temperature measurement 23
IV. Options 24
15. Options screen 25
15.1. Functions 25
15.2. Memory 25
15.3. Miscellaneous 25
15.4. Info 27
16. Memorising readings, memory readout 28
16.1. Entering readings into the memory 28
16.2. Viewing and deleting readings 29
17. Power, replacing the rechargeable batteries 30
18. Technical data 31
19. Ordering information 32
20. Technical service 33
21. Warranty 33
22. Equipment disposal 34


I. INTRODUCTION

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VWR Collection DO-230 dissolved oxygen meter instruction manual v1.0x
1. PACKAGE CONTENT
The standard set includes:
1. DO-230 dissolved oxygen meter.
2. Dissolved oxygen sensor with temperature sensor.
3. Accessories for the sensor: two membranes, electrolyte – 30 ml,
sodium sulphite – 50 g.
4. Plastic case.
5. 5V/1000mA power adapter.
2. EXPLOITATION NOTICES
Dear User!
Wide range of additional functions requires careful reading of the
manual, in other case some of the features may stay unused or using
the meter may be troublesome.
Accuracy of oxygen measurements depends on the sensor’s calibration and
regular conservation which consists in replacing the membranes, electrolyte
and cleaning the electrodes. Neglecting these activities after some time
would make measurements impossible. Please turn your attention to
the fact that stable measurement is possible only with natural or
simulated water flow.
We wish a pleasant and trouble-free work with our meter.
3. CHARACTERISTICS OF THE METER
Two kinds of power source: the rechargeable battery and the power adapter,
enable work in field and long-lasting measurements in laboratory. The meter’s
memory is independent from power supply. Waterproof housing enables
working in difficult conditions. Minimised size and weight facilitate field work.
The most important features of DO-230 are:
- measuring of oxygen dissolved in water in % or mg/l, oxygen content in air
in % and temperature of solutions or air in 0C, 0F or K;
- automatic and manual temperature compensation;
- compensation of the salinity and the atmospheric pressure influence on the
oxygen concentration measurement;
- storing of the calibration date and parameters of oxygen sensor;
- possibility of introducing the date of calibration validity termination and
signalising its expiry;
- cooperation with Pt-1000 resistor temperature sensor;
- signalising of the reading stabilisation;
- storing measurement results with time and date;
- real time clock with date;
- automatic switch off after time set by the user.

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4. THE OUTSIDE VIEW
On the front wall of the meter there is a graphic LCD placed (Pic. 1), which
displays the following measurement functions:
- oxygen concentration measurement in % or mg/l;
- temperature measurement.
At the top of the LCD the current time and date are displayed.
Choosing particular functions is described in the chapter 6.1. Symbols of the
units are displayed next to the reading.
Pic. 1.
The automatic temperature compensation is signalised by the symbol, the
manual compensation – by the symbol (next to the temperature reading).
The exclamation symbol (Pic. 1.) is displayed on the left in the following
situations marked with the colours:
yellow - the calibration validity date expired;
red - characteristic erase, the sensor calibration necessary.
The rechargeable battery condition is signalised by the symbol.

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VWR Collection DO-230 dissolved oxygen meter instruction manual v1.0x
The button (Pic. 2) placed below the display is used for switching the
meter on and off.
In case of recording readings, the button is locked until the recording
process is stopped or finished.
In the upper wall of the meter connectors are placed with the symbols given
below:
F-BNC-50 input for connecting the dissolved oxygen sensor;
t-Chinch input to connect the temperature probe;
P- input for connecting the power adapter;
Pic. 2.

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5. THE METER‘S MAINTENANCE
The meter is equipped with a graphic touch screen. The maintenance
consists in pressing particular keys and windows which appear on the
screen. Grey captions in the windows and keys inform that these elements
are not active in this particular operating mode. Particular keys, connected
with the measurement function (i.e. or ) become active after
selecting the chosen function. To select, press the screen in a freely chosen
spot of the chosen function. Around this spot a frame will display. To
deselect, press the spot again. If the chosen function has a possibility of
calibration, the key becomes active. If it has additional parameters,
the key also becomes active. The key is the only key in the
meter that responds exclusively to a long press (about 2 sec.). It prevents
from accidental erase of the electrode (sensor, cell) calibration data.
Entering incorrect value, attempt of calibration when the meter doesn‘t
recognise the standard or attempt to turn the meter off when the result
memorising proceeds are signalised by a triple warning sound, irrespective of
the chosen sound settings.

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VWR Collection DO-230 dissolved oxygen meter instruction manual v1.0x
6. SWITCHING THE METER ON AND OFF
After switching the meter on with the button, the memory test proceeds.
If the test ends successfully, the meter enters the measurement screen with
settings entered before switching it off previously. In case of detecting the
manufacturer‘s calibration data loss, the following information will appear:
Pressing the button accepts standard manufacturer‘s calibration
parameters and enters the measurement screen. Such situation will be
repeating each time the meter is switched on and requires sending the meter
to the manufacturer for servicing.
In case of the user‘s data loss (i.e. the oxygen sensor characteristic), the
following information will appear:
Pressing the button accepts and records in the memory standard pH
electrode characteristic and enters the measurement screen. In such case,
calibration of the pH electrode is necessary. Analogical situation occurs in
case of other measuring functions. Repeating of the situation after switching
the meter on again informs about the EEPROM memory malfunction and
requires sending the meter to the manufacturer for servicing.
Switch the meter off by pressing the button. If the meter is powered only
by the internal rechargeable battery, it turns off after the time of non-use set
by the user (description in the chapter 15.3). This function is deactivated
during calibration, while memorising results and connecting with a computer
or power adapter.

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6.1. Stabilised reading
The stabilised reading signalisation is active only for the reading marked with
a frame. If the measured value meets the criterium of the stabilised reading, it
is signalised by green colour of the frame and additionally with a sound if it
has been activated. In this mode the meter does not record changes of the
measured value in a certain range and does not display them. The meter
escapes the stabilised reading mode after exceeding this range, the frame
changes its colour to white and the meter displays the current measurement
value.
To choose the stabilised reading signalisation, on the measurement screen
press the button, the options screen will display with the FUNCTIONS
tab open containing the previously set configuration (Pic. 3A).
A B
Pic. 3
The window for choosing the stabilised reading signalisation mode is placed
below (Pic. 3B):
- the stabilised reading signalisation is off;
- the stabilised reading signalised with changing the frame
colour from white to green (only for reading marked with a
frame);
- the stabilised reading signalised by colour change and
sound.
Return to the measurement screen by pressing the button.

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VWR Collection DO-230 dissolved oxygen meter instruction manual v1.0x
7. PREPARATION TO WORK
Before starting measurements:
- connect the oxygen sensor to the F (BNC-50) connector;
- if work with temperature probe is planned, connect it
to the t (Chinch/RCA) temperature connector;
- if work with power adapter is planned, connect it to the P input;
- switch the meter on by pressing the button.
7.1. Choosing the kind of the temperature compensation
The meter switches to the automatic or manual temperature compensation
mode itself. Connecting the temperature probe switches the automatic
temperature compensation on. Next to the reading the symbol is displayed.
After disconnecting the probe the meter enters the manual temperature
compensation mode. Instead of the symbol the is displayed. In case of
the manual temperature compensation the temperature value is set on the
temperature measurement parameters screen.

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II. OXYGEN CONCENTRATION MEASUREMENT

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VWR Collection DO-230 dissolved oxygen meter instruction manual v1.0x
8. BASIC INFORMATION ABOUT THE OXYGEN MEASUREMENT
Measurement of dissolved oxygen in water solutions is performed with use of
the oxygen sensor. The basic element of the sensor is a teflon semi-
permeable membrane, which enables penetration of oxygen contained in the
measured solution, into the electrolyte – inside of the sensor. The sensor
generates a cell; the cell’s voltage depends on the oxygen content in the
electrolyte.
The meter enables measurement of oxygen concentration in water solutions
in % and in mg/l and measurement of oxygen saturation in air in %.
Calculation of the mg/l value is based on the saturation measurement in %
and the temperature measurement. During mg/l measurements, the salinity
and atmospheric pressure parameters should be additionally entered. The
measurement of saturation in % does not depend on these factors.
The quality of the oxygen sensor has a major effect on the
measurement accuracy. Complications arising during measurements
are caused mainly (98%) by the sensor, not the device. In many cases,
the problems are the result of neglecting basic sensor maintenance
activities by the user. It is worth remembering that during measurement the
sensor absorbs oxygen from the environment of the membrane.
The sensor’s manufacturers recommend the minimal flow-rate of the
tested water, assuring a stable result. When this requirement is not
complied, the result will regularly decrease. During measurements in
stagnant solutions the flow can be partly simulated by keeping the sensor in
slow rotary motion. In laboratory conditions, i.e. performing measurements in
a vessel, the flow can be forced with a magnetic stirrer. However, when
measuring low O2 saturation, intensive stirring can cause increase of oxygen
content in the tested solution. Transferring water samples to the laboratory
can alter their O2 concentration. The best results can be achieved only in
conditions recommended by the manufacturer of the sensor in the
operation manual.
Long-lasting storage of the sensor without performing any measurements
(more than 2 months) requires removing the electrolyte. After this period the
container must be filled with a fresh electrolyte and the sensor stored in
distilled water for about 24 hours.

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Accurate measurement result is determined by the condition of the
membrane. The membrane must be free of any cracks (appearing of
electrolyte-drops or white spots when dry). Before measurement the sensor
should be activated by storing in distilled water for about 15 minutes. Strongly
polluted wastewater after some time causes clogging of the membrane,
which is recognised by inability to calibrate the device at 100% oxygen
content (the calibration range becomes too narrow). In both cases the
membrane should be replaced according to the manufacturer’s instructions.
When replacing the membrane and replenishing the electrolyte it is important
to pay attention if there are no air bubbles in the container beneath the
membrane, because otherwise the measurements would be falsified. In such
case the container should be twisted off and the bubbles removed by tapping
it against the table, next the electrolyte should be refilled and the sensor
assembled.
Depending on thickness of the membrane, awaiting time for a stable result is
about 1 - 1,5 min. Accuracy of the measurement is connected with the
temperature of calibration and measurement. The greater the difference of
these temperatures, the greater the measurement error. For measurements
of concentration in the range 30 ÷ 80%, it is sufficient to make one-point
calibration in 100% oxygen concentration. For measurements in solutions
with low oxygen content (about a few %) the calibration should be also made
in 0% solution. Clean water contains about 60 ÷ 80% oxygen. Waste water
and chemical solutions are in general less saturated with oxygen but liquids
with forced aeration are much more saturated than clean water. When
performing accurate measurements, the sensor’s manufacturers recommend
carrying out calibration just before the measurement since after some time
the sensor’s parameters are changing. Even the best oxygen sensors have
so-called drift about ±1%/24 h. Wide measuring range in the DO-320 meter
enables making measurements in water permeated with oxygen, i.e. with
blooming and growing plants, where during the photosynthesis process large
quantities of oxygen are produced.

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VWR Collection DO-230 dissolved oxygen meter instruction manual v1.0x
9. ENTERING THE OXYGEN MEASUREMENT PARAMETERS
The oxygen meter parameters screen is entered by pressing the oxygen
reading (the frame will display around it – Pic. 4A), and next the
button. On this screen (Pic. 4B) choose the unit and the salinity and the
atmospheric pressure value. After entering parameters, return to the
measurement screen pressing the button.
ABC
Pic. 4
9.1. Unit
The reading can be displayed in % of the oxygen saturation or in mg/l. By
pressing the UNIT window, choose:
- measurement of the oxygen concentration in water in %
- measurement of the oxygen concentration in water in mg/l
- measurement of percantage of the oxygen content in air.
9.2. Calibration points and date
After pressing the button the screen with calibration points, validity
time and last calibration date. Marker next to the point value informs, that the
last calibration was performed in this particular point. The calibration points
values are fixed and cannot be changed.

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9.3. Calibration validity time
The meter stores the calibration validity time of the oxygen sensor.
Termination of this time is signalised with yellow sensor number. To set the
calibration validity time, press the VALIDITY window, the numerical keyboard
will appear to enter the number of days and confirm with the button.
9.4. The salinity influence compensation
Oxygen solubility in water is decreased by its salinity which has to be taken
into consideration during measurements in mg/l. 1 g/l of salinity change
causes about 0.5% of the oxygen saturation change. The meter enables
entering the salinity value in g/l and counts the change of oxygen saturation
in mg/l.
9.4.1. Manual introduction of the salinity value
The salinity value may be determined on the basis of the conductivity value of
the measured solution. Table 1 shows the real dependence between
conductivity and salinity in conversion to NaCl.
After choosing the manual mode the SALINITY window will appear (Pic. 4C)
for entering the salinity value. To enter, press the SALINITY window, the
numerical keyboard will appear for entering the salinity value and confirm
with the button.
Measurement in % does not require entering the salinity value.

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VWR Collection DO-230 dissolved oxygen meter instruction manual v1.0x
mS/cm g/l mS/cm g/l mS/cm g/l
1 0.49 28 16.87 55 34.34
2 1.00 29 17.52 56 34.99
3 1.52 30 18.17 57 35.64
4 2.08 31 18.82 58 36.28
5 2.63 32 19.46 59 36.93
6 3.19 33 20.11 60 37.58
7 3.74 34 20.76 61 38.23
8 4.29 35 21.41 62 38.87
9 4.85 36 22.05 63 39.52
10 5.40 37 22.70 64 40.17
11 6.00 38 23.35 65 40.81
12 6.61 39 23.99 66 41.46
13 7.21 40 24.64 67 42.11
14 7.83 41 25.29 68 42.75
15 8.45 42 25.93 69 43.40
16 9.07 43 26.58 70 44.05
17 9.70 44 27.23 71 44.70
18 10.35 45 27.87 72 45.34
19 11.01 46 28.52 73 45.99
20 11.66 47 29.17 74 46.64
21 12.31 48 29.82 75 47.28
22 12.96 49 30.46 76 47.93
23 13.61 50 31.11 77 48.58
24 14.26 51 31.76 78 49.22
25 14.91 52 32.40 79 49.87
26 15.56 53 33.05 80 50.63
27 16.22 54 33.70
Table 1. Determining the salinity in g/l NaCl on the basis of conductivity
in mS/cm (at the temperature 25oC).

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9.5. Atmospheric pressure influence compensation
The concentration of oxygen saturated in water determined in mg/l
depends directly on the atmospheric pressure value, which means that
10% pressure change causes also 10% oxygen saturation change. If the
atmospheric pressure value differs significantly from 1013 hPa, it should be
calculated into the measurement. The meter enables introducing of the
atmospheric pressure value and calculates it into changes in the oxygen
concentration.
9.5.1. Entering the atmospheric pressure value
To enter the atmospheric pressure value, press the PRESSURE window (Pic.
4C), the pressure values will appear to choose and confirm with the
button.
Measurement in % does not require entering the
atmospheric pressure value.

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VWR Collection DO-230 dissolved oxygen meter instruction manual v1.0x
10. CALIBRATION OF THE OXYGEN SENSOR
The meter cooperates with a galvanic membrane sensor of our production
with measurement accuracy equal ±1%, provided that the measurement is
performed at the same temperature as calibration. The bigger the difference
in the measurement and calibration temperature, the lower the accuracy. It is
3% when the temperature difference is ±5 0C and 5% for the difference
±10 0C. The calibration is performed to eliminate the measurement error
arising from the individual characteristic of the sensor and should be
repeated always before measurement with new sensor, after replacing the
membrane or in case of high measurement accuracy requirements.
Characteristic feature of sensors is a „signal drift“, which means that the
longer interval between calibration and measurement, the lower
measurement accuracy. Calibration is also recommended if temperature of
the tested solution differs significantly from temperature in which the probe
was calibrated, because then an additional error arises. In such case it is
recommended to prepare calibration solutions having approximate
temperature to the predicted temperature of the tested solutions.
If it is impossible to calibrate the device, the membrane of the sensor should
be replaced according to the manufacturer’s instruction. This situation usually
takes place if the membrane is strongly polluted or ruptured (sometimes
almost invisibly). After replacing the membrane the sensor should be
conditioned in water for 24 hours. Applied oxygen sensors require 1- or 2-
point calibration in standard solutions. The meter has two values of the
calibration points recorded: P1=0% and P2=100%. 2 point calibration is
carried out in 0% of oxygen concentration solution (i.e. saturated sodium
sulphide) and calibration in 100% of oxygen saturation is made in the air. In
such case the membrane has to be immersed in distilled water for a
few minutes before calibration. It is assumed that O2 content in the air
corresponds to 100% of saturation, what enables simplified calibration to be
carried out.
1 point calibration is made only for 100% of oxygen saturation.
In case of measurement of oxygen content in air let the fresh air in into the
room. Usually, 1-point calibration in air is sufficient, as the zero point of the
meter is at its resolution level.
Entering the calibration mode under the chosen sensor number erases
the characteristic stored in the memory under this number.
In case of choosing the sensor’s number, entering the calibration mode
and escaping it without making calibration, the characteristic stored
previously will be erased and a standard characteristic will be applied.
The characteristic erase is signalised with red coulour of the sensor
number on the screen.
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