Zebra-Tech D-Opto User manual

D-Opto Logger
Dissolved Oxygen Logger
Operation Manual

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Table of contents
1Introduction....................................................................................................3
1.1 Optical Sensor Technology.....................................................................3
2Software ........................................................................................................4
2.1 Installation ..............................................................................................4
2.2 Operation................................................................................................4
3Operation.......................................................................................................9
3.1 Installation ..............................................................................................9
3.2 Sealing the D-Opto Logger .....................................................................9
3.3 Logging Endurance ................................................................................9
3.4 Routine Maintenance............................................................................10
3.5 Calibration ............................................................................................11
Appendix 1: Data File Format ......................................................................13
Appendix 2: Communication Cable Wiring Scheme ....................................14
Appendix 3: LED flash sequence codes ......................................................15
Appendix 4: Trouble shooting ......................................................................16
Appendix 5: Specifications...........................................................................17
Appendix 6: Pressure correction chart.........................................................18
Appendix 7: Useful Conversions..................................................................19

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1 Introduction
The D-Opto Logger is a fully self contained dissolved oxygen logger,
incorporating a DO sensor, battery, and low power data logger in a rugged
compact underwater housing.
The D-Opto Logger uses a field-proven solid-state optical sensing system to
measure dissolved oxygen that is highly stable over long periods of time, even in
harsh conditions. The data is stored onboard in non-volatile memory. The D-Opto
Logger is setup, and data offloaded using simple Windows based software,
supplied with the instrument.
1.1 Optical Sensor Technology
Unlike conventional dissolved oxygen sensors, the D-Opto Logger sensing
element utilises fluorescence to measure dissolved oxygen. The basic principle
involves subjecting a fluorescing compound (ruthenium) to a fixed wavelength of
light. When the light source is removed, the compound emits a fluorescence, the
intensity of which is dependent on the oxygen levels present in the surrounding
water. An extremely stable electronic circuit has been designed to firstly excite
the ruthenium, and then measure the intensity of the resulting fluorescence.
Therefore using this circuitry, the D-Opto Logger should provide accurate
dissolved oxygen measurements over long periods of time (many months)
without re-calibration.
Unlike conventional polarographic dissolved oxygen sensors, the optical method
does not consume oxygen. Consequently the measurement of dissolved oxygen
by the D-Opto Logger is unaffected by water movement. Similarly the D-Opto
Logger does not utilise a membrane or any other consumables, thus minimising
servicing requirements.

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2 Software
The D-Opto Logger is supplied with the custom designed Windows based
communication software program “D-OptoLog”. This software:
•Enables the user to communicate with the D-Opto Logger via a computer;
•Is used to setup the D-Opto Logger prior to deployment;
•Is used to download data from the D-Opto Logger to the PC after retrieval.
2.1 Installation
The D-Opto Logger is supplied with a software CD that contains the file “Install
D-OptoLogX.exe” (X = version number). Double clicking the file from Windows
Explorer will initiate installation onto the PC. There are no restrictions or
limitations on the distribution and installation of the D-OptoLog software.
During installation, the user can select the working path and directory, however it
is recommended that the default is used (“c:\Program Files\D-OptoLog”).
2.2 Operation
The D-Opto Logger is supplied with a communication cable. This cable has a 9
pin serial plug on one end, and a 3.5mm jack plug on the other end.
The 9 pin plug is plugged into the serial plug on the PC. If the PC does not have
a serial port, a USB to serial adaptor can be used. This adaptor plugs into the
USB port on the PC, and has a serial port that the communication cable 9 pin
plug can be plugged into.
The jack plug on the communication cable is plugged into the communication
socket, located inside the D-Opto Logger housing. This is accessed by removing
the D-Opto Logger end cap.
When D-OptoLog is started and the current port is unavailable, a port selection
window opens (Figure 1).

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Figure 1: D-OptoLog serial port selection window.
With most computers the D-Opto Logger will be connected to com port number 1.
However, if the D-Opto Logger is connected to the computer’s USB port via a
USB to serial converter, the port number will probably be either com port 4 or 5.
The selected com port is maintained in an configuration file on the PC.
Once the correct port has been selected, and the ‘OK’ button pressed, the
computer will start communicating with the D-Opto Logger. This may take up to 8
seconds, and when communication has begun the D-OptoLog main window will
open (Figure 2).

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Figure 2: D-OptoLog main window
The main window displays current dissolved oxygen (% saturation and PPM) and
temperature (°C) data, and is updated approximately once every second.
The serial number displayed is factory set and is unique to each D-Opto Logger.
It corresponds to the number displayed on the outside of the D-Opto Logger
housing.
The logger setup section enables the operator to set the desired logging
parameters.
The “Plot” button enables a graphical plot of historic D-Opto Logger data to be
displayed on the screen.
The “Calibration” button opens the D-Opto Logger Calibration window (Figure 4).
All calibration values are calculated and stored internally by the D-Opto Logger.
The “Restore Defaults” button causes the D-Opto Logger to resort back to the
original factory calibrations. A full description of the calibration procedure is
outlined in the operation section.
The “Altitude Correction” button opens up the Pressure Correction Calculator
which provides a tool for pressure correcting the dissolved oxygen saturation

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content of fully aerated water (Figure 5). It will accept either altitude (m) or
barometric pressure (mBar).
By pressing the “Restore defaults” button, the original factory calibration values
are reinstated by the D-Opto Logger.
Figure 4: D-OptoLogger Calibration window.

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Figure 5: Pressure Correction Calculator

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3 Operation
3.1 Installation
A new battery should always be used when starting a deployment. Good quality
alkaline batteries such as, Duracell or Energizer, should always be used.
The D-Opto Logger can be mounted in any orientation. The body can be
clamped in position; however avoid using excessive force. A safety wire can be
attached to the eyelet swivel on the top cap of the logger. It is not recommended
that the D-Opto Logger is suspended solely from the eyelet swivel.
3.2 Sealing the D-Opto Logger
The D-Opto Logger end cap features a dual “O” ring sealing system. It is
essential that these “O” rings are properly serviced and maintained; otherwise
moisture may penetrate the housing.
The “O” rings must be cleaned and lubricated each time the end cap is replaced,
prior underwater deployment.
1) Using the “O” ring pick supplied, remove the “O” rings from the inside of
the end cap and the body of the D-Opto Logger
2) Using a lint free tissue, clean the “O” ring seats, the corresponding “O”
ring surfaces, and both “O” rings
3) Lightly grease both “O” rings with the grease supplied with the D-Opto
Logger.
4) Replace the “O” rings, ensuring no hairs or particles become trapped
under them.
5) Screw the end cap onto the D-Opto Logger body. Do not over tighten.
3.3 Logging Endurance
The D-Opto Logger can log 10,080 data records into non-volatile memory. Each
data record consists of the time and date, battery voltage, dissolved oxygen
percent saturation, PPM and temperature (See appendix 1).
Data is retained in the non-volatile memory until a new logging session is started,
at which point the memory is cleared of the previous data.
Memory logging endurance for different logging intervals are shown in table1. In
reality battery power may limit the deployment duration, not memory capacity.

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The D-Opto Logger will operate correctly until the battery voltage drops below
around 7.0 volts. If this occurs whilst the D-Opto Logger is in logging mode, the
last set of data values in the data file will be set to zero, and the D-Opto Logger
enters a low power sleep mode, with no further data values being logged.
Logging Interval
(minutes)
Memory Endurance (Days)
Standard D-Opto Logger
1 7
5 35
10 70
15 105
30 210
60 420
Table 1. Memory endurance
3.4 Routine Maintenance
As with all instruments, it is good operating practice to make regular checks on
the quality of data being generated by the D-Opto Logger. This can be carried
out on site, using one of the following two methods:
1. Place a recently calibrated transportable dissolved oxygen sensor next to
the D-Opto Logger and compare the measurements. It is important to
allow a sufficient period of time for temperature equilibration to occur.
2. Place the D-Opto Logger in a solution of known dissolved oxygen content.
A solution of 0% dissolved oxygen saturation can be created by adding a
few teaspoons of sodium sulfite to 1 litre of distilled or fresh tap water.
The D-Opto Logger can tolerate some biofouling, however where possible steps
should be taken to minimise this; for example covering the D-Opto Logger can
reduce the amount of bio-growth by restricting available light. . The copper
biofouling control ring should reduce bio-growth in the area around the optical
window; this ring is sacrificial and may require replacement on an occasional
basis. Always use the nylon bolts supplied with the replacement ring to attach the
ring to the D-Opto Logger, and avoid over tightening.
Periodically it may be necessary to clean the D-Opto optical window, to remove
bio-growth or other accumulated deposits. DO NOT use a brush or any object
that may scratch or damage the optical window. Only use the cleaning pads
supplied with the D-Opto.

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3.5 Calibration
Under normal operating conditions, the D-Opto Logger should only require
infrequent calibration.
Calibration of the D-Opto Logger is a simple operation that can be carried out in
the field. Due to the measurement principle of the D-Opto Logger, performing air
calibrations are not advisable. The Zebra-Tech Do-Cal Kit greatly simplifies the
field calibration of the D-Opto Logger.
The offset and gain of the D-Opto Logger are calibrated individually. Normally
only the offset will need to be calibrated as the gain is even more stable than the
offset over time. The gain should only be calibrated AFTER the offset has been
calibrated.
When calibrating the D-Opto Logger, take care not to allow water to enter into the
instrument.
•Offset Calibration
A reference solution of 0% dissolved oxygen is required for the offset
calibration. This can be created by mixing a couple of teaspoons of
sodium sulfite into 1 litre of distilled or fresh tap water.
Procedure:
1) Place the D-Opto Logger in the reference solution and allow
equilibrating for at least 30 minutes.
2) Power up the D-Opto Logger, and start D-OptoLog. Once the
measurements have stabilised, press the “Calibrate” button in the main
window.
3) Enter 0 (zero) in the offset calibration edit box and press the “Reset
offset” button.
4) The D-Opto Logger performs a calibration routine followed by a self
check; this can take up to 30 seconds. Do not remove the D-Opto
Logger from the reference solution during this period. The operator will
be notified when the process is complete.
•Gain Calibration
A solution of known dissolved oxygen content, other than 0%, should be
used for the gain calibration. The most practical method is to create a fully
aerated solution. This can be done by bubbling air through a container of
distilled or fresh tap water, stirring frequently. After around 30 minutes,
the water can be assumed to be fully saturated.
The actual dissolved oxygen saturation can be calculated by correcting for
altitude, or preferably, the local barometric pressure if that is known. The
“Correction Calculator” can be used to calculate the corrected dissolved
oxygen content of the fully aerated reference solution. As an example, if

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the D-Opto Logger is installed at a field site at 435 meters above sea level,
and a fully aerated reference solution is prepared on site, the actual
dissolved oxygen percent saturation is calculated at 95%.
Procedure:
1) Place the D-Opto Logger is placed in the reference solution, and
allow it to equilibrate for at least 30 minutes.
2) Power up the D-Opto Logger and start D-OptoLog. Once the
measurements have stabilised, press the “Calibrate” button in the
main window to open the Calibration window.
3) Enter the pressure corrected dissolved oxygen percent saturation
of the reference solution in the gain calibration edit box and press
the “Reset gain” button.
4) The D-Opto performs a calibration routine followed by a self check;
this can take up to 30 seconds. Do not remove the D-Opto Logger
from the reference solution during this period. The operator will be
notified when the process is complete.

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Appendix 1: Data File Format
Data Field Number Description
1 Year
2 Month
3 Day
4 Hour
5 Minute
6 Second
7 Battery voltage
8 Temperature (Degrees C)
9 Dissolved Oxygen (%)
10 Dissolved Oxygen (ppm)

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Appendix 2: Communication Cable Wiring Scheme

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Appendix 3: LED flash sequence codes
Inside the D-OptoLogger housing, next to the battery and communication socket,
there is an LED. The LED flashes according to the current status of the D-
OptoLogger. The interval between the flashing sequence may be up to 8
seconds.
1 Flash = Operational
2 Flash = Delayed start
3 Flash = Not operational, waiting for PC communications
4 Flash = Memory full
5 Flash = Low battery shut down

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Appendix 4: Trouble shooting
The PC starts to communicate with the D-Opto Logger, but then looses
communication.
•Replace the D-Opto Logger battery
The D-Opto Logger is not communicating with the PC
•Check the battery voltage.
•Check the communications cable is plugged into the correct serial port on
the PC
Dissolved oxygen readings are highly erratic, but temperature readings are
stable.
The D-Opto Logger incorporates a high gain amplification circuit to measure the
fluorescence of the optical window. The instrument has been carefully designed
to prevent electrical interference impacting on the operation. Under extreme
conditions however, noise may become a problem.
•Track down the source of noise; this could be a nearby pump or other
motor.
•If the D-Opto Logger is being bench tested in a small container of water,
noise can be caused by a lack of suitable earthing. Place a grounding wire
from the water to the D-Opto Logger power ground.
•The D-Opto Logger is supplied with built in noise rejection specific for the
country of supply. If the D-Opto Logger is being used in a country other
than the country it was supplied to, contact your supplier.
The last data record in the data file consists of zero values.
•The D-Opto Logger battery ran critically flat.

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Appendix 5: Specifications
Physical Dimensions
200mm long x 50mm diameter
Accuracy
Temperature: +/- 0.1 deg C
DO: 1% of reading or 0.02 PPM, which ever is greater
Resolution
Temperature: 00.01 Deg C
DO saturation: 000.01%
PPM: 00.001 ppm
Sensor Drift
< 1% per year (provided measurement interval ≥10 minutes)
Power supply
1 x PP9 - 9 volt alkaline battery. Duracell or Energizer recommended
Power consumption
12 mA during measurement, 0.07 mA between measurements
Memeory Capacity
128 KB
10080 data records
Depth rating
Maximum 30 m water depth
“O” Rings
2 of #128 (1 ½” x 3/32” )

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Appendix 6: Pressure correction chart
Dissolved oxygen % saturation values of air saturated fresh water, corrected for
atmospheric pressure.
Altitude
(m)
Altitude
(feet)
Barometric pressure
(mBar) % Saturation
0 0 1013 100
85 278 1003 99
170 558 993 98
256 841 983 97
343 1126 973 96
431 1413 963 95
519 1703 952 94
608 1995 942 93
698 2290 932 92
789 2587 922 91
880 2887 912 90
972 3190 902 89
1066 3496 899 88
1160 3804 882 87
1254 4115 871 86
1350 4430 861 85
1447 4747 851 84
1544 5067 841 83
1643 5391 831 82
1743 5717 821 81
1843 6047 811 80
1945 6381 800 79
2047 6717 790 78
2151 7058 780 77
2256 7401 770 76
2362 7749 760 75
2469 8100 750 74
2577 8455 740 73
2687 8815 730 72
2797 9178 719 71
2909 9545 709 70
3023 9917 699 69
3137 10293 689 68

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Appendix 7: Useful Conversions
Convert from To Calculation
kPA mBar Multiply by 10
inHg mBar Multiply by 33.85
Feet Meters Multiply by 0.3048
° Centigrade Fahrenheit (9/5 °C)+32

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Zebra-Tech Ltd
Contact Details
PO Box 1668
Nelson
New Zealand
Tel: [phone]
Fax: [phone]
Email: [email protected]