TPS pH Cube User manual

Congratulations !
You have purchased the latest in benchtop pH-mV-Temperature instrumentation.
We trust that your new pH Cube will give you many years of reliable service.
The pH Cube 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 pH Cube. It also contains a full listing of all of the items that you should
have received with your pH Cube. 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 pH Cube,
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
Email :
[email protected]
Web Site : www.tps.com.au
Model pH Cube
pH-mV-Temp.
Meter
Handbook Version : 1.1
Date : 17-May-05
Author : AB

Page 1
Contents
1. Introduction..................................................................................................2
1.1 pH Cube Front Panel and Controls........................................................................2
1.2 pH Cube Side Panel and Connectors .....................................................................3
1.3 Unpacking Information..........................................................................................4
1.4 Specifications.........................................................................................................4
2. Operating Modes..........................................................................................5
3. pH Calibration...............................................................................................6
3.1 Calibration Procedure ............................................................................................6
3.2 Calibration Notes...................................................................................................7
4. mV Calibration..............................................................................................7
5. Temperature Calibration .............................................................................8
5.1 Calibration Procedure ............................................................................................8
5.2 Calibration Notes...................................................................................................8
5.3 Manual Temperature Setting..................................................................................8
6. Troubleshooting...........................................................................................9
6.1 pH and mV Troubleshooting .................................................................................9
6.2 Temperature Troubleshooting..............................................................................10
7. Appendices.................................................................................................11
7.1 pH Buffer Values Vs Temperature......................................................................11
7.2 pH Sensor Fundamentals .....................................................................................12
7.3 Checking the reference junction of a pH sensor. .................................................14
7.4 Determining if an instrument or sensor is faulty..................................................15
8. Warranty......................................................................................................16

Page 2
1. Introduction
1.1 pH Cube Front Panel and Controls
Display
•12.7mm LED display with mode enunciator.
Function Switch
•Switches between pH, mV and Temperature modes. See section 2.
Calibrate Control
•Used for pH asymmetry calibration in pH6.88 or pH7.00 buffer. See section
3.
Slope Control
•Used for pH slope calibration in a buffer that is at least 2 to 3 pH away from
pH7.00, eg. pH4.00, pH9.23 or pH10.00. See section 3.
Manual Temp Control
•Used to manually set the temperature of the solution for pH temperature
compensation. Only active when temperature sensor is unplugged. See
section 5.3.

Page 3
1.2 pH Cube Side Panel and Connectors
pH / mV Connector
•Used to connect pH, Redox (ORP) and Specific Ion sensors.
Ref Connector
•Used to connect Reference sensor when a mono pH, Redox (ORP) or
Specific Ion sensor is connected to the pH / mV Connector.
Temp Connector
•Used to connect Temperature sensor. This sensor provides temperature
readout as well as Automatic Temperature Compensation for pH readings.
Temp Cal Control
•Used for temperature calibration. See section 5.
12V DC Power Connector
•Used to connect 12V AC/DC Adaptor. The pH Cube can run off any 12V
DC source with at least 200mA output. The 12V DC connector has a
positive tip.

Page 4
1.3 Unpacking Information
Before using your new pH Cube, please check that the following accessories
have been included: Part No
1. pH Cube pH-mV-Temperature Instrument 121122
2. Combination pH Sensor 121207
3. Temperature/ATC Sensor 121245
4. pH6.88 Buffer, 200mL 121306
5. pH4.00 Buffer, 200mL 121381
6. Rod and Clamp for 2 x 12mm and 1 x 6mm 121346
diameter sensor.
7. AC/DC Power Adaptor 130044
8. pH Cube Handbook 130050
1.4 Specifications
Ranges Resolution Accuracy
pH 0 to 14.00 pH 0.01 pH ±0.01 pH
mV 0 to ±1999 mV 1 mV ±1 mV
Temperature -10.0 to 120.0 OC 0.1
OC ±0.2 OC
Input Impedance : >3 x 1012 Ω
Asymmetry Range : Approx -1.00 to 1.00 pH
Slope Range : Approx 85.0 to 105.0%
Temperature Compensation : Automatic : 0 to 100.0 oC
Manual : 5 to 100 oC
Power : 12V DC by AC/DC power adaptor.
Dimensions : 120 x 120 x 120 mm
Mass : Instrument only : Approx 0.9 kg
Full Kit : Approx 2.1 kg
Environment Temperature : 0 to 45 oC
Humidity : 0 to 90 % R.H.

Page 5
2. Operating Modes
Switch the function switch to any one of the following three operating modes.
Note the mode enunciator – Pfor pH, Efor EMF (mV), and Cfor OC.
Function Switch
Position Display example
pH
mV
Temp

Page 6
3. pH Calibration
3.1 Calibration Procedure
1. Switch the pH Cube to pH mode (see section 2).
2. Plug the pH sensor into the Sensor socket and the temperature sensor into
the Temp socket.
3. Ensure that temperature has already been calibrated or manually set (see
sections 5.1 and 5.3).
4. Remove the wetting cap from the pH sensor.
5. Rinse the pH and Temperature sensors in distilled water and blot them dry.
6. Place both sensors into a small sample of primary buffer that is at or near
pH7 (eg. pH6.88 or pH7.00). The bulb and reference junction should both be
covered, as per the diagram below.
DO NOT place the sensors directly into the buffer bottle.

Page 7
7. When the reading has stabilised, adjust the Calibrate control until the
display shows the value of the buffer at the current temperature. For TPS
buffers, this is shown on the bottle. Refer also to the table in section 7.1.
8. Rinse the pH and Temperature sensors in distilled water and blot them dry.
9. Place both sensors into a small sample of secondary buffer (eg. pH4.00,
pH9.23 or pH10.00) so that the bulb and reference junction are both
covered, as per the diagram in step 6 above.
DO NOT place the sensor 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.
When the reading has stabilised, adjust the Slope control until the display
shows the value of the buffer at the current temperature. For TPS buffers,
this is shown on the bottle. Refer also to the table in section 7.1.
10. The pH Cube is now calibrated and is ready for use.
Discard the used samples of buffer.
3.2 Calibration Notes
1. A 1-point calibration using the Calibrate control in a pH6.88 or pH7.00
buffer should be performed at least weekly. In applications where the sensor
junction can become blocked (eg. wines, dairy products, mining slurries etc) a
1-point calibration may have to be done daily.
2. A full 2-point calibration should be performed at least monthly. Of course,
more frequent calibration will result in greater confidence in results.
4. mV Calibration
The mV section is factory calibrated. There is no user-calibration facility for this
mode.

Page 8
5. Temperature Calibration
The temperature readout must be calibrated or manually set before attempting pH
calibration.
5.1 Calibration Procedure
1. Switch the pH Cube to Temperature mode (see section 2).
2. Plug the temperature sensor (Part No 121245) into the Temp socket.
3. Place the sensor alongside a good quality mercury thermometer into a
beaker of room temperature water. Stir the sensor and the thermometer
gently to ensure an even temperature throughout the beaker.
4. When the reading has stabilised, adjust the Temp Cal. control until the
display shows the same temperature as the mercury thermometer.
5. The Temperature function of the pH Cube is now calibrated and is ready for
use.
5.2 Calibration Notes
1. Temperature does not need to be recalibrated unless the Temperature sensor
is replaced.
5.3 Manual Temperature Setting
Manual temperature setting is only available if the temperature sensor is not
plugged in.
1. Switch the pH Cube on and select Temperature mode (see section 2).
2. Measure the temperature of the sample solution.
3. Adjust the Manual Temp control until the display shows the measured
temperature of the sample solution.

Page 9
6. Troubleshooting
6.1 pH and mV Troubleshooting
Symptom Possible Causes Remedy
Meter displays
“-1. " as a
reading.
pH reading is over-ranged. pH sensor not connected or
faulty. Replace sensor if
necessary.
Asymmetry
calibration with
Calibrate control
in pH6.88 or
pH7.00 buffer fails.
(Asymmetry is
greater than +/-1.00
pH.)
1. Reference junction blocked.
(See section 7.3)
2. Reference electrolyte
contaminated.
Clean reference by immersing
the probe in hot water (60°C)
for a few minutes. Proteins can
be cleaned off using a pepsin
solution.
Replace electrolyte if using a
refillable sensor.
Slope calibration
with Slope control
in low or high
buffer fails. (Slope
is less than 85.0%.)
1. Glass bulb not clean.
2. Sensor is aged.
3. Connector is damp.
4. Buffers are inaccurate.
Clean glass bulb as per
instructions supplied with the
sensor.
Attempt rejuvenation, as per
instructions supplied with the
sensor. If not successful,
replace sensor.
Dry in a warm place.
Replace buffers.
Inaccurate readings,
even when
calibration is
successful.
Reference junction blocked.
(See section 7.3)
Clean reference junction by
immersing the probe in hot
water (60°C) for a few minutes.
Displays around
pH7.00 for all
solutions.
Electrical short in connector. 1. Check connector. Replace if
necessary.
2. Replace sensor.
Displays 4-5 pH for
all solutions. Glass bulb or internal stem cracked. Replace sensor.

Page 10
pH and mV Troubleshooting, continued…
Unstable readings. 1. Reference junction blocked.
2. Glass bulb not clean.
3. Bubble in glass bulb.
4. Faulty connection to meter.
5. Reference junction not
immersed.
6. KCl crystals around
reference junction, inside
the electrolyte chamber.
Clean reference junction as per
instructions supplied with the
sensor.
Clean glass bulb as per
instructions supplied with the
sensor.
Flick the sensor to remove
bubble.
Check connectors. Replace if
necessary.
Ensure that the bulb AND the
reference junction are fully
immersed.
Rinse electrolyte chamber with
warm distilled water until
dissolved.
6.2 Temperature Troubleshooting
Symptom Possible Causes Remedy
Meter reads
“-1 ” in
Temperature mode.
Temperature sensor is
connected, but is faulty. Check the temperature sensor connector and replace if
necessary.
Replace temperature sensor
(part no 121245) if problem
persists.
Temperature
readings do not vary
and Manual Temp
control is active
when temperature
sensor is plugged in.
1. Faulty connector.
2. Incorrect temperature
sensor.
3. Faulty temperature sensor.
Check the connector and
replace if necessary.
Fit new temperature sensor, part
number 121245.
Fit new temperature sensor, part
number 121245.
Temperature
inaccurate and
cannot be
calibrated.
1. Faulty connector.
2. Faulty temperature sensor.
Check the connector and
replace if necessary.
Fit new temperature sensor, part
number 121245.

Page 11
7. Appendices
7.1 pH Buffer Values Vs Temperature
The following table lists the pH values of some popular buffers, with respect to
Temperature. Any pH meter should always be calibrated to the correct value of
the buffers at the current solution temperature.
Temp OC pH4.00 pH6.88 pH7.00 pH9.23 pH10.00
0 4.00 6.98 7.13 9.46 10.32
5 4.00 6.95 7.09 9.40 10.25
10 4.00 6.92 7.06 9.33 10.18
15 4.00 6.90 7.04 9.28 10.12
20 4.00 6.88 7.02 9.23 10.06
25 4.01 6.87 7.00 9.18 10.01
30 4.01 6.85 6.99 9.14 9.97
35 4.02 6.84 6.98 9.10 9.93
40 4.03 6.84 6.97 9.07 9.90
45 4.04 6.83 6.97 9.04 9.89
50 4.05 6.83 6.97 9.01 9.83
55 4.06 6.83 6.97 8.99
60 4.08 6.84 6.97 8.96
65 4.10 6.84 6.97 8.94
70 4.12 6.85 6.97 8.92
75 4.14 6.85 6.97 8.90
80 4.16 6.86 6.97 8.88
85 4.18 6.87 6.97 8.87
90 4.21 6.88 6.96 8.85
95 4.24 6.89 6.96 8.88
100 4.27 6.90 6.96 8.82

Page 12
7.2 pH Sensor Fundamentals
A combination pH sensor is two sensors in one. The sensing membrane is the
round or spear shaped bulb at the tip of the sensor. This produces a voltage that
changes with the pH of the Solution. This voltage is measured with respect to the
second part of the sensor, the reference section. The reference section makes
contact with the sample solution using a salt bridge, which is referred to as the
reference junction. A saturated solution of KCl is used to make contact with the
sample. It is vital that the KCl solution has an adequate flow rate in order to
obtain stable, accurate pH measurements.
7.2.1 Asymmetry of a pH Sensor
An “ideal” pH sensor produces 0 mV output at 7.00 pH. In practice, pH sensors
generally produce 0 mV output at slightly above or below 7.00 pH. The amount
of variance from 7.00 pH is called the asymmetry. Figure 7-1 illustrates how
asymmetry is expressed.
-600
-400
-200
0
200
400
600
0714
+1.00 pH Asymmetry
0.00 pH Asymmetry
-1.00 pH Asymmetry
Response of pH Electrode, as a Function of Asymmetry
Electrode Response (mV)
pH
Figure 7-1

Page 13
7.2.2 The Slope of a pH Sensor
As mentioned above, a pH sensor produces 0 mV output at around 7.00 pH. As
the pH goes up, an “ideal” pH sensor produces -59mV/pH unit at 25 oC As the
pH goes down, an ideal pH sensor produces +59mV/pH unit. In practice, pH
sensors usually produce slightly less than this. The output of a pH sensor is
expressed as a percentage of an ideal sensor. For example, an ideal sensor that
produces 59mV/pH unit has “100% Slope”. An sensor that produces
50.15mV/pH unit has “85% Slope” (see Figure 7-2).
-600
-400
-200
0
200
400
600
0714
85%Slope at 25 oC
(50.15mV/pH)
100%Slope at 25 oC
(59mV/pH)
Response of pH Electrode, as a Function of Slope
Electrode Response (mV)
pH
Figure 7-2

Page 14
7.2.3 Temperature Compensation
The slope of a pH sensor (section 7.2.2) is affected by temperature. This effect is
compensated for either by using an Automatic Temperature Compensation
(ATC) sensor or by entering the sample temperature manually. Figure 7-3 shows
the slope of a pH sensor at various temperatures.
-600
-400
-200
0
200
400
600
0714
Electrode
Potential (mV) at
0 oC (54mV/pH)
Electrode
Potential (mV) at
50 oC (64mV/pH)
Electrode
Potential (mV) at
100 oC (74mV/pH)
pH Electrode Response, as a Function of Temperature
Electrode Response (mV)
pH
Figure 7-3
7.3 Checking the reference junction of a pH sensor.
If pH readings are inaccurate or unstable, the reference junction of the sensor
may be blocked. The following test can be performed to determine if the
reference junction of a pH sensor is making adequate contact with the sample
solution.
1. Calibrate the pH Cube, as per section 3.
2. Dilute 1 part of pH6.88 buffer with 9 parts of distilled water.
3. Measure the pH of the diluted buffer. The result should be 7.06 +/-0.05 pH.
4. If the value obtained is outside of these limits, then clean the reference
junction as per the instructions supplied with the pH sensor.
5. Re-calibrate the pH Cube and repeat the test.
6. If the value obtained is still outside 7.06 +/-0.05 pH, then the sensor should be
replaced.

Page 15
7.4 Determining if an instrument or sensor is faulty
The following test can be performed to help determine if the pH Cube or the pH
sensor is faulty.
1. Set the Calibrate control approximately to the centre (as it is shown in the
diagram in section 1.1.
2. Disconnect the pH sensor.
3. Connect the centre pin of the Sensor connector with the outside frame of the
connector, using a short piece of wire or a paper clip etc.
4. If the pH Cube is operating correctly, the reading should be totally stable at
around pH7.00 with the wire firmly in place. If not, the meter requires
servicing.
5. Now carefully disconnect the wire from the centre pin only (make sure the
other end of the wire remains connected to the outside frame of the
connector).
6. The reading should steadily drift away from 7.00 (either up or down) at a rate
of approximately 1 pH or less every 3 seconds. If the drift rate is faster than
this, then input circuitry of the pH Cube may be faulty and could require
servicing.

Page 16
8. Warranty
TPS Pty. Ltd. guarantees all instruments and sensors to be free from defects in
material and workmanship when subjected to normal use and service. This
guarantee is expressly limited to the servicing and/or adjustment of an instrument
returned to the Factory, or Authorised Service Station, freight prepaid, within
twelve (12) months from the date of delivery, and to the repairing, replacing, or
adjusting of parts which upon inspection are found to be defective. Warranty
period on sensors is three (3) months.
There are no express or implied warranties which extend beyond the face hereof,
and TPS Pty. Ltd. is not liable for any incidental or consequential damages
arising from the use or misuse of this equipment, or from interpretation of
information derived from the equipment.
Shipping damage is not covered by this warranty.
PLEASE NOTE:
A guarantee card is packed with the instrument or sensor. This card must be
completed at the time of purchase and the registration section returned to TPS
Pty. Ltd. within 7 days. No claims will be recognised without the original
guarantee card or other proof of purchase. This warranty becomes invalid if
modifications or repairs are attempted by unauthorised persons, or the serial
number is missing.
PROCEDURE FOR SERVICE
If you feel that this equipment is in need of repair, please re-read the manual.
Sometimes, instruments are received for "repair" in perfect working order. This
can occur where batteries simply require replacement or re-charging, or where
the sensor simply requires cleaning or replacement.
TPS Pty. Ltd. has a fine reputation for prompt and efficient service. In just a few
days, our factory service engineers and technicians will examine and repair your
equipment to your full satisfaction.
To obtain this service, please follow this procedure:
Return the instrument AND ALL SENSORS to TPS freight pre-paid and insured
in its original packing or suitable equivalent. INSIST on a proof of delivery
receipt from the carrier for your protection in the case of shipping claims for
transit loss or damage. It is your responsibility as the sender to ensure that TPS
receives the unit.

Page 17
Please check that the following is enclosed with your equipment:
•Your Name and daytime phone number.
•Your company name, ORDER number, and return street address.
•A description of the fault. (Please be SPECIFIC.)
(Note: "Please Repair" does NOT describe a fault.)
Your equipment will be repaired and returned to you by air express where
possible.
For out-of-warranty units, a repair cost will be calculated from parts and labour
costs. If payment is not received for the additional charges within 30 days, or if
you decline to have the equipment repaired, the complete unit will be returned to
you freight paid, not repaired. For full-account customers, the repair charges will
be debited to your account.
•Always describe the fault in writing.
•Always return the sensors with the meter.