TPS WP-91 User manual

Congratulations !
You have purchased the latest in Handheld Dissolved Oxygen-pH-mV-
Temperature instrumentation. We trust that your new WP-91 will give
you many years of reliable service.
The WP-91 is a breeze to operate. This manual has been designed to
help you get started, and also contains some handy application tips. If
at any stage you require assistance, please contact either your local
TPS representative or the TPS factory in Brisbane.
The manual is divided into the following sections:
1. Table of Contents
Each major section of the handbook is clearly listed. Sub-sections
have also been included to enable you to find the information you
need at a glance.
2. Introduction
The introduction has a diagram and explanation of the display and
controls of the WP-91. It also contains a full listing of all of the items
that you should have received with your WP-91. Please take the
time to read this section, as it explains some of items that are
mentioned in subsequent sections.
3. Main Section
The main section of the handbook provides complete details of the
WP-91, including operating modes, calibration, troubleshooting,
specifications, and warranty terms.
4. Appendices
Appendices containing background information and application
notes are provided at the back of this manual.
TPS Pty Ltd
4 Jamberoo Street
Springwood, Brisbane,
Australia, 4127
Phone : [phone]
International : 61 7 32 900 400
Fax : [phone]
International : 61 7 3808 4871
E-mail : [email protected]
Web Site : www.tps.com.au
Model WP-91
Dissolved Oxygen –
pH –mV –Temp Meter
Version : 1.2
Date : 31-Oct-2003
Author : MS

Page 2Contents
1. Introduction ..............................................................................................4
1.1 WP-91 Display and Controls ...............................................................4
1.2 Unpacking Information ........................................................................6
1.3 Specifications......................................................................................7
2. WP-91 Menu Structure............................................................................10
3. Oxygen Operating Modes ......................................................................11
4. Dissolved Oxygen Calibration ...............................................................13
4.1 Calibration Procedure........................................................................13
4.2 Measurement Notes:.........................................................................15
4.3 Calibration Notes...............................................................................15
4.4 Calibration Messages........................................................................16
5. pH Calibration.........................................................................................17
5.1 Calibration Procedure........................................................................17
5.2 Calibration Notes...............................................................................19
6. mV Calibration........................................................................................19
7. Temperature Calibration ........................................................................20
7.1 Calibration Procedure........................................................................20
7.2 Calibration Notes...............................................................................20
7.3 Calibration Messages........................................................................21
8. Salinity Correction..................................................................................22
9. Altitude or Atmospheric Pressure Correction.......................................23
9.1 Selecting Altitude or Pressure Correction ..........................................23
9.2 Changing the Altitude or Pressure Correction value...........................24
9.3 Notes ................................................................................................25
10. Good Laboratory Practices (GLP)......................................................26
10.1 To recall GLP information on the display.......................................26
10.2 Failed Calibration..........................................................................28
10.3 Printing GLP Information to the RS232 Port..................................29
10.4 Instrument Serial Number..............................................................30
10.5 Additional GLP Features ...............................................................30
11. Notepad Function...............................................................................31
11.1 Recording Readings into the Notepad............................................31
11.2 Recalling Records from the Notepad.............................................31
11.3 Erasing Records from the Notepad................................................32
11.4 Printing Records from the Notepad to the RS232 Port...................33
12. Automatic Datalogging.......................................................................34

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13. RS232 Port...........................................................................................36
13.1 Setting the Baud Rate ...................................................................36
13.2 Sending Readings to the RS232 Port ............................................36
13.3 RS232 Configuration.....................................................................36
13.4 Communication and Statistical Software........................................36
13.5 Commands....................................................................................38
13.6 Data Format..................................................................................39
13.7 GLP Data Format..........................................................................40
13.8 Importing Data into Microsoft Excel...............................................41
14. Battery Saver Function.......................................................................43
15. Recharging the Battery.......................................................................44
16. Clock Function....................................................................................45
16.1 Setting the Clock...........................................................................45
16.2 Displaying or Hiding the Clock.......................................................45
17. Selecting pH6.88 or pH7.00 as the Primary Buffer............................46
18. Initialising the WP-91..........................................................................47
19. Instrument firmware version number. ...............................................47
20. Troubleshooting.................................................................................48
20.1 General Errors...............................................................................48
20.2 Dissolved Oxygen Troubleshooting ...............................................49
20.3 pH and mV Troubleshooting..........................................................50
20.4 Temperature Troubleshooting........................................................51
21. Dissolved Oxygen Sensor Fundamentals.........................................52
21.1 Operating Principle........................................................................52
21.2 Maintenance Of The Membrane....................................................53
21.3 Probe Storage...............................................................................53
21.4 Notes On Units Of Dissolved Oxygen............................................54
21.5 Equilibrium Conditions...................................................................55
21.6 Velocity Past The Membrane.........................................................56
22. pH Sensor Fundamentals...................................................................57
22.1 Asymmetry of a pH Sensor............................................................57
22.2 Slope of a pH Sensor ....................................................................58
22.3 pH Temperature Compensation.....................................................59
22.4 Checking the reference junction of a pH sensor.............................59
22.5 Determining if a pH meter or an sensor is faulty............................60
23. Warranty..............................................................................................61

Page 4
1. Introduction
1.1 WP-91 Display and Controls

Page 5
Press to record readings into memory. See section 11.1. Also used
to switch the Altitude or Atmospheric Pressure Correction system on
or off. See section 9.1.
Press to alternate temperature, date/time, and manual
Salinity/Altitude/ Pressure values on the display. See section 16.2.
Also used to select pH6.88 or pH7.00 as the primary pH buffer
(section 17).
Press to start or stop automatic logging. See section 12.
Alternatively, press to transmit current reading plus date and time to
the RS232 port (optional) See section 13.2.
Only used within the menu system on the WP-91.
Press to access the user-friendly menu system which makes the
WP-91 easy to operate.
and
The and keys are used for calibrating temperature readout
(section 7.1), setting the clock (section 16.1), setting the automatic
logging period (section 12), and displaying GLP information (section
10.1). The key is also used to initialise the WP-91 at turn-on. See
section 18.
Switches the WP-91 on and off.
Display
32 character alpha-numeric display with user-friendly menu and
prompting system. Shows Dissolved Oxygen, pH/mV and
Temperature simultaneously. Date, time, manual salinity value,
altitude or pressure can also be displayed.

Page 6
1.2 Unpacking Information
Before using your new WP-91, please check that the following
accessories have been included:
Part No
1. WP-91 Dissolved Oxygen-pH-Temp Instrument..................123150
2. pH6.88 Buffer, 200mL .........................................................121306
3. pH4.00 Buffer, 200mL .........................................................121381
4. Battery charger....................................................................130037
5. WP-91 Handbook ................................................................130050
Options that may have been ordered with your WP-91:
1. YSI Dissolved Oxygen-Temperature Sensor.......................123204
2. 3m Cable for DO2Sensor....................................................123221
3. Combination pH Sensor, 1m................................................121207
4. Combination Redox Sensor, 1m..........................................121262
5. Temperature Sensor, 1m.....................................................121253
(when Dissolved Oxygen sensor not in use)
6. RS232 Serial Interface Option (includes cable)...................130039
7. WinTPS Communication software for Windows 95 & Later.130086
8. Hard Carry Case..................................................................130059
9. Battery charger lead for 12V cigarette lighter socket...........130046
10. Solar Panel..........................................................................130012
11. RS232 Printer......................................................................130031
Other spares:
1. 6V NiCad Battery.................................................................130038
2. RS232 Interface Cable ........................................................130041
3. Membrane, Filling Solution & Zero DO2Kit..........................123300
4. Sodium Sulphite for Zero DO2calibration, 50g....................123302
5. Filling Solution for EDYSI Sensor, 45mL .............................123307

Page 7
1.3 Specifications
ModeRange* Resolution Accuracy
Dissolved Oxygen
ppM (mg/L) 0 to 20.00 ppM
20.0 to 40.0 ppM 0.01 ppM 0.1 ppM ±0.2% of full scale of selected
range
Dissolved Oxygen
% Saturation 0 to 240.0 % Sat
240 to 450 % Sat 0.1 % Sat 1 % Sat ±0.3% Saturation
% Gaseous Oxygen 0 to 45.0 % Gas
45 to 100 % Gas 0.1% Gas 1 % Gas ±0.1 % Gaseous
pH 0 to 14.00 pH 0.01 pH ±0.01 pH
mV 0 to +/-500.0 mV
0 to ±1500 mV 0.15 mV 1 mV ±0.3 mV ±1 mV
Temperature -10.0 to 120.0 OC±0.1 OC±0.2 OC
*Oxygen ranges subject to sensor performance.
Additional Dissolved Oxygen Specifications
Salinity Correction.........................User-set, from 0 to 50.0 ppK NaCl
Barometric Pressure Correction...User-set, from 800 to 1100 HPa
Altitude Correction.........................User-set, from 0 to 5000m
Temperature Compensation .........Dual automatic temperature
compensation system.
DO2Sensor Span Range...............70 to 135%
DO2Sensor Zero Range................0 to 7.5%
Automatic Calibration....................Zero in Sodium Sulphite (Na2SO3)
Solution Span in Air.
Additional pH Specifications
Input Impedance............................>3 x 1012 Ω
Asymmetry Range..........................-1.00 to 1.00 pH
Slope Range...................................85.0 to 105.0 %

Page 8
Temperature Compensation .........Automatic, 0 to 100 OC

Page 9
Additional Temperature Specifications
Temp. Sensor Offset Range.....-10.0oC to +10.0oC
General Specifications
Memory......................................150 readings including date and time
Automatic Logging ...................User-set for one reading every 1 to 90
seconds, minutes or hours.
RS232 Output (optional)...........300, 1200 & 9600 baud.
8 bits, no parity, 1 stop bit, XON/XOFF
Protocol.
Clock..........................................Calendar clock displays date, month,
hours, minutes & seconds.
Year is recorded in memory and
transmitted to optional RS232 port, but
is not displayed.
Battery Saver ............................On :Auto switch-off after 5 minutes
Off :Continuous use
Bar Graph display of battery charge
level.
Readout of battery voltage available for
troubleshooting.
Good Laboratory Practices......Date, Time and Value of last Dissolved
Oxygen, pH and Temperature
calibration are stored, along with
Altitude or Pressure setting at time of
calibration. This information can be
recalled or sent to the optional RS232
port at any time.
Power.........................................6V NiCad Rechargeable Battery for
approx 75 hours operation.
Dimensions ...............................187 x 110 x 51 mm
Mass...........................................Instrument only:Approx 440g
Full Kit :Approx 2.0 kg
Environment..............................Temperature :0 to 45 oC
Humidity :0 to 90 % R.H.

Page 10
2. WP-91 Menu Structure
A detailed breakdown of the menu system of the WP-91 is shown below.
This diagram provides a quick reference for the menu functions available
for the WP-91.
Menu →F1:Cal. →F1:Oxy
F2:Temp
F3:pH (not available in mV mode)
F4:Sal
or F4:Altitude
or F4:Pressure
or F4:Comp. →F1:Sal
(see sections 8& 9)F2:Altitude
or F2:Pressure
→F2:Notepad →F1:Recall
F2:Erase
F3:Print *
F4:Prog →F1:Min
F2:Sec
F3:Hr
↑↓:Set
→F3:Mode →F1:ppM →Man Sal Comp
F1:OFF
or F2:ON
F2:%Sat
F3:%Gas
F4:mV
or F4:pH
→F4:Setup →F1:Batt →F1:OFF
F2:ON
F2:Clock
F3:GLP →F1:Recall
F3:Print *
F4:Baud * →F1:300
F2:1200
F3:9600
* These functions available when RS232 option is fitted.

Page 11
3. Oxygen Operating Modes
The WP-91 has three Oxygen modes : ppM (mg/L), % Saturation, and
% Gaseous.
To select an Oxygen mode, access the mode menu by pressing , then
F3:Mode.
1. F1:ppM (ppM (mg/L) readout)
Displays ppM Dissolved Oxygen, pH/mV and Temperature and the
user-set Salinity value simultaneously. See section 8for details on
setting the Salinity correction value.
See section 16.2 for details on how to alternate temperature and
date.
10.00 M 7.00
25.0 12:00:00
2. F2:%Sat (% Saturation readout)
Displays % Saturation Dissolved Oxygen, pH/mV and Temperature
readings simultaneously.
See section 16.2 for details on how to alternate temperature and
date.
100.0%S 7.00
25.0 12:00:00
3. F3:%Gas (% Gaseous readout)
Displays % Gaseous Oxygen, pH/mV and Temperature readings
simultaneously.
See section 16.2 for details on how to alternate temperature and
date.
20.9%G 7.00
25.0 12:00:00
4. Notes
1) If the temperature of the solution exceeds 120.0 oC, or the
temperature sensor inside the dissolved oxygen sensor is faulty,
the temperature reading is replaced by “OVRoc”, to signify the over-
range condition.

Page 12
2) The decimal point is replaced by a “∗∗”if a Dissolved Oxygen, pH or
Temperature calibration has failed (sections 4, 5& 7) or if the unit
is initialised (section 18).

Page 13
4. Dissolved Oxygen Calibration
4.1 Calibration Procedure
1. Plug the Dissolved Oxygen sensor into the Dissolved Oxygen
socket.
2. Switch the meter on.
3. Select the mode of your choice. ( →F3:Mode →F1 to F3).
4. Ensure that temperature has already been calibrated (see section 7).
NOTE: A “∗∗” in place of the decimal point in the temperature readout
indicates that temperature is not calibrated.
5. Rinse the Dissolved Oxygen sensor in distilled water and blot dry.
6. Zero Calibration
a) Place the sensor into an oxygen-free solution. This solution may
be prepared by dissolving 2g of Sodium Sulphite in 100mL of
distilled water. A 50g bottle of Sodium Sulphite powder is supplied
with a new Dissolved Oxygen sensor for this purpose (part number
123302).
b) Allow the reading to stabilise at or near zero. This may take 2-3
minutes.
c) Select Oxygen Calibration. ( →F1:Cal. →F1:Oxy).
d) Press the key to calibrate.
e) A “∗” will not be removed from the display after a Zero Calibration.
7. Rinse the Dissolved Oxygen sensor in distilled water and blot dry.
8. Air Calibration
a) Hang the Dissolved Oxygen sensor in air. The tip of the sensor
should be pointing downwards.
b) Allow the reading to stabilise. After a zero calibration, this may
take up to 5 minutes.
c) Select Oxygen Calibration. ( →F1:Cal. →F1:Oxy).
d) Press the key to calibrate.
e) A “∗” in the display will be replaced by a decimal point after a
successful air calibration.

Page 14
9. The WP-91 is now calibrated ready for Dissolved Oxygen
measurement.

Page 15
4.2 Measurement Notes:
1. When taking sample measurements, always ensure that there is
adequate flow of solution past the membrane for accurate, stable
readings. See section 21.6.
2. If salinity-corrected ppM Dissolved Oxygen readings are required, set
the salinity correction value before taking sample measurements. See
section 8.
3. If Altitude or Atmospheric Pressure Correction is selected, set the
correction value before calibrating and taking measurements. See
section 9.
4.3 Calibration Notes
1. A zero calibration should be performed at least monthly, or when the
membrane is replaced. In applications where there is a low level of
dissolved oxygen, a zero calibration may have to be done weekly.
2. An air calibration should be performed at least weekly, or when the
membrane is replaced. Of course, more frequent calibration will result
in greater confidence in results.
3. The salinity correction value is ignored during zero and air calibration.
There is therefore no need to re-set the salinity correction value when
calibrating Dissolved Oxygen.
4. For optimum accuracy, set the altitude of atmospheric pressure
before calibration.
5. All calibration information is retained in memory when the WP-91 is
switched off, even when the battery is removed. This information can
be recalled or printed later using the GLP function (see section 10).

Page 16
4.4 Calibration Messages
1. If a Zero calibration has been successfully performed, the WP-91 will
display the following message, and the zero value of the sensor.
Zero Cal. OK
Zero= 0.0%
2. If an Air calibration has been successfully performed, the WP-91 will
display the following message, and the span value of the sensor.
Air Cal. OK
Span=100.0%
3. If an Air calibration has failed, the WP-91 will display the following
message, and the failed span value of the sensor.
Air Cal. Fail
Span= 65.0%

Page 17
5. pH Calibration
5.1 Calibration Procedure
1. Plug the pH sensor into the pH/mV socket. The Dissolved Oxygen
sensor (or a Temperature sensor) should be plugged into the
Dissolved Oxygen socket.
2. Switch the meter on.
3. Select pH Mode. ( →F3:Mode →F4:pH).
4. Ensure that temperature has already been calibrated (see section 7).
NOTE: If the decimal point in the temperature reading is shown by a
∗, then the temperature readout is not calibrated.
5. Remove the wetting cap from the pH sensor.
6. Rinse the pH and Dissolved Oxygen/Temperature sensors in distilled
water and blot them dry.
7. Ensure that you are using the primary buffer for which the WP-91
has been set (see section 17).
Place both sensors into a small sample of pH6.88 (or pH7.00) buffer,
so that the bulb and reference junction are both covered, as per the
diagram over the page.
DO NOT place the sensors directly into the buffer bottle.
To reduce the amount of pH buffer that is consumed, the Dissolved
Oxygen sensor may be placed into a separate beaker of water that is
at the same temperature as the buffer.

Page 18
8. Select pH Calibration ( →F1:Cal. →F3:pH).
9. When the reading has stabilised, press the key to calibrate. If a 1
point calibration has been performed, the “ ∗∗ “ will not be removed
until a full 2 point calibration has been performed.
10. Rinse the sensors in distilled water and blot them dry.
11. Place both sensors into a small sample of pH4.00, pH9.23 or
pH10.00 Buffer, so that the bulb and reference junction are both
covered as per the diagram in step 8, above. DO NOT place the
sensors directly into the buffer bottle.
NOTE: pH9.23 and pH10.00 buffers are highly unstable. Avoid
using these buffers if possible. Discard immediately after use.
12. Select pH Calibration ( →F1:Cal. →F3:pH).
13. When the reading has stabilised, press the key to calibrate. The ∗
will now be replaced by a decimal point, if calibration was successful.
14. The WP-91 is now calibrated for pH and is ready for use. Discard the
used samples of buffer.

Page 19
5.2 Calibration Notes
1. If a 1-point calibration has been successfully performed, the WP-91
will display the following message, and the asymmetry of the sensor.
1 Point Cal. OK
Asy= 0.10pH
2. If a 1-point calibration has failed, the WP-91 will display the following
message, and the failed asymmetry value of the sensor.
1 Point Cal.Fail
Asy= 1.50 or 1 Point Cal.Fail Asy=-1.50
3. If a 2-point calibration has been successfully performed, the WP-91
will display the following message, and the asymmetry and slope of
the sensor.
2 Point Cal. OK
Asy= 0.10pH then 2 Point Cal.OK Slope=100.0%
4. If a 2-point calibration has failed, the WP-91 will display the following
message, and the failed slope value of the sensor.
2 Point Cal.Fail
Slope=130.0% or 2 Point Cal.Fail Slope= 70.0%
6. mV Calibration
The mV section is factory calibrated. There is no user-calibration facility
for this mode.

Page 20
7. Temperature Calibration
7.1 Calibration Procedure
1. Plug the Dissolved Oxygen/Temperature sensor into the Dissolved
Oxygen socket.
2. Switch the meter on.
3. Place the sensor into a beaker of room temperature water, alongside
a good quality mercury thermometer. Stir the sensor and the
thermometer gently to ensure an even temperature throughout the
beaker.
4. Select Temperature Calibration.( →F1:Cal. →F2:Temp).
5. The reading from the probe is now displayed on the right of the
display, and the value you are going to set is shown on the left.
> 25.0< 20∗∗0oc
↑↑↓↓:Set F1:Cal.
6. When the reading on the right has stabilised, press the and
keys until the reading on the left shows the same temperature as the
mercury thermometer.
7. Press the key to calibrate the temperature readout.
The ∗will now be replaced by a decimal point, if calibration was
successful.
Alternatively, press the key to abort temperature calibration.
7.2 Calibration Notes
1. Temperature calibration information is retained in memory when the
WP-91 is switched off, even when the battery is removed. This
information can be recalled or printed later using the GLP function
(see section 10).
2. Temperature does not need to be recalibrated unless the sensor is
replaced or the meter is initialised.