YOKOGAWA PH72 User manual

User’s
Manual
IM 12B03D02-01E
Model PH72
Personal pH/ORP Meter
IM 12B03D02-01E
5th Edition

1
Preface
IM 12B03D02-01E
5th Edition: June 2021 (YK)
All Rights Reserved, Copyright © 2004, Yokogawa Electric Corporation
Preface
Thank you for purchasing the Model PH72 Personal pH/ORP Meter. Please read this
manual thoroughly before using the meter.
The related documents (User's Manual) are as follows.
IM 12B03D02-01E Model PH72 Personal pH/ORP Meter (this manual)
IM 12B03D02-02E Model PH72 Personal pH/ORP Meter Quick Manual
* the “E” in the document number is the language code.
The following symbol marks are used for safety precautions in this manual.
WARNING : Indicates that serious injury may result, if the user fails to
follow instructions.
CAUTION : Indicates that minor injury to personnel, or damage
to the equipment, may result if the user fails to follow
instructions.
WARNING
Do NOT use this instrument where there is a possibility of electrical shock.
Do NOT touch any part of the electrode immediately after using in very hot liquids —
otherwise, you may get burned.
CAUTION
Do not apply physical shock or excessive force to the glass sensor, or it may break.
If the meter will not be used for an extended period of time, be sure to remove the
batteries. Otherwise battery leakage may occur, causing damage to or malfunction of
the meter.
The contents of this manual are subject to change without prior notice.
Yokogawa Electric Corporation assumes no liability for damage, defects, or loss of the
product caused by any of the following:
Misuse by the user;
Inappropriate or out-of-specications use of the product;
Use in an unsuitable environment;
Repair or modication of this or related products by persons other than Yokogawa-
authorized engineers.

IM 12B03D02-01E
2
Preface
nLiquid Crystal Display (LCD) Characters
On the LCD alphanumeric characters are displayed as follows.
9
8
7
6
5
4
3
2
1
0
Z
Y
X
W
V
U
T
S
R
Q
P
O
N
M
L
K
J
I
H
G
F
E
D
C
B
A
Alphabet Display Alphabet Display DisplayNumerals
F00.ai
All display segments
nNote Regarding Panels Shown in this Manual:
Panels shown in this manual should be regarded as examples. Actual panel format
may vary depending on parameter settings and on type of connected sensor.
nFlashing Displays
Flashing messages, numbers and digits on the display are indicated in gray in this
manual.
Flashing state: Lit state:

IM 12B03D02-01E 3
Preface
nWarranty and Service
Yokogawa products and parts are guaranteed to be free from defects in workmanship
and materials under normal use and service for a period of (typically) 12 months from
the date of shipment from the manufacturer.
Individual sales units may o󰀨er di󰀨erent warranty periods, so the original purchase
order should be consulted for the conditions of sale. Damage caused by normal
wear and tear, inadequate maintenance, corrosion, or due to chemical processes, is
excluded from this warranty coverage. In addition, performance deterioration of the
sensor caused by the operating environment mentioned above is not considered to
be a defect. Yokogawa cannot carry out repairs in such a case so please replace the
sensor.
In the event of a warranty claim, any items that are considered to be defective should
be sent (freight paid) for repair or replacement (at Yokogawa discretion) to the service
department of the relevant sales unit. The following information must be included in a
letter accompanying the returned items:
Model code and serial number
Copy of original purchase order showing the date
Length of time used, and the measuring environment
Fault symptoms, and circumstances of failure
Statement whether service under warranty or out-of-warranty service is requested
Complete shipping and billing instructions for return of goods, plus the name and
phone number of a contact person who can be reached for further information
Goods that have been in contact with process uids must be decontaminated /
disinfected before shipment, and a statement to this e󰀨ect should be included. Safety
data sheets for all process components that the goods have exposed to should also
be included.

IM 12B03D02-01E
4
Preface
nHow to replace and dispose the batteries:
This is an explanation about the new EU Battery Directive (DIRECTIVE 2006/66/EC).
This directive is only valid in the EU.
Batteries are included in this product.
When you remove batteries from this product and dispose them, discard them in
accordance with domestic law concerning disposal.
Take a right action on waste batteries, because the collection system in the EU on
waste batteries are regulated.
Battery type: Alcaline dry cell
Notice:
The symbol (see above), which is marked on the batteries, means they shall be
sorted out and collected as ordained in ANNEX II in DIRECTIVE 2006/66/EC.
How to remove batteries safely: Refer to subsection "2.1 Installing the Batteries".
n How to dispose this product (This directive is valid only in the EU.)
This product complies with the WEEE Directive marking requirement.
This marking indicates that you must not discard this electrical/electronic
product in domestic household waste.
Product Category
With reference to the equipment types in the WEEE directive Annex
I, this product is classied as a “Monitoring and Control instruments”
product.
Do not dispose in domestic household waste. When disposing products
in the EU, contact your local Yokogawa Europe B. V. o󰀩ce.
n Authorised Representative in EEA
The Authorised Representative for this product in EEA is Yokogawa Europe B.V.
(Euroweg 2, 3825 HD Amersfoort, The Netherlands).

IM 12B03D02-01E Toc-1
Contents
CONTENTS
Preface ..........................................................................................................................1
1. Outline ................................................................................................................ 1-1
1.1 Features .......................................................................................................................... 1-1
1.2 Specications .................................................................................................................. 1-2
1.3 When You Receive the PH72 Meter Package................................................................ 1-4
1.4 PH72 Meter Kit................................................................................................................ 1-5
1.5 PH72 Meter — Part Names and Functions.................................................................... 1-6
1.6 Sensors — Types, Part Names and Functions............................................................... 1-6
1.7 Spare Parts ..................................................................................................................... 1-8
2. Preparation......................................................................................................... 2-1
2.1 Installing the Batteries..................................................................................................... 2-1
2.2 Connecting the Sensor Cable......................................................................................... 2-2
2.3 Setting the Date and Time .............................................................................................. 2-2
2.4 Selecting pH or ORP Measurement................................................................................ 2-3
2.5 Wetting Cap..................................................................................................................... 2-4
2.6 Manual Temperature Setting ........................................................................................... 2-4
2.7 pH Calibration.................................................................................................................. 2-4
3. Measurement...................................................................................................... 3-1
3.1 Precautions...................................................................................................................... 3-1
3.2 Measurement Procedures ............................................................................................... 3-2
3.3 Measurement Display Panel ........................................................................................... 3-3
3.4 Saving a Measured Value ............................................................................................... 3-3
4. Calibration .......................................................................................................... 4-1
4.1 Automatic Calibration ...................................................................................................... 4-2
4.2 Manual Calibration .......................................................................................................... 4-4
5. Keypad and Display Functions ........................................................................ 5-1
5.1 Keypad Functions............................................................................................................ 5-1
5.2 Display Items................................................................................................................... 5-2
5.3 Function Mode................................................................................................................. 5-4
6. Maintenance ....................................................................................................... 6-1
6.1 For Optimum Meter Performance ................................................................................... 6-1
6.2 pH Electrode Cleaning .................................................................................................... 6-1
6.3 Sensor Replacement....................................................................................................... 6-3
6.4 Rehydrating the Glass Electrode .................................................................................... 6-3
6.5 Point to note when performing calibration or measurement........................................... 6-3
6.6 Replenishing the Electrode with Filling Solution (KCl solution)...................................... 6-4
6.7 Cleaning and Drying Connectors.................................................................................... 6-5
6.8 Storage and O-ring/Gasket Replacement....................................................................... 6-6
7. Troubleshooting................................................................................................. 7-1
7.1 Causes of Abnormal Readings and Errors ..................................................................... 7-1
7.2 Error Messages, Possible Causes, and Corrective Actions ........................................... 7-2
7.3 Causes of Abnormal Measured Values........................................................................... 7-5
7.4 Other Conditions ............................................................................................................. 7-5
8. ORP Meter .......................................................................................................... 8-1
8.1 ORP Measurement.......................................................................................................... 8-1
8.2 Maintenance of ORP Sensors......................................................................................... 8-2
8.3 Checking the ORP Sensor.............................................................................................. 8-2
9. Technical Information........................................................................................ 9-1
9.1 Measurement Principle of pH Meter (Glass Electrode Method)..................................... 9-1
9.2 Relationship between EMF of Glass Membrane and pH Value ..................................... 9-2
9.3 Temperature Compensation ............................................................................................ 9-4
9.4 The Asymmetry Potential ................................................................................................ 9-5

IM 12B03D02-01E
Toc-2
Contents
9.5 The Alkaline Error............................................................................................................ 9-5
9.6 The Acid Error ................................................................................................................. 9-7
9.7 Calibration Calculation .................................................................................................... 9-7
9.8 ORP (Oxidation-Reduction Potential).............................................................................. 9-8
9.9 Reference Electrode........................................................................................................ 9-9
9.10Wetted Part Materials of Sensors ................................................................................. 9-11
9.11 References .................................................................................................................... 9-12
Appendix.............................................................................................................. App-1
Revision Record............................................................................................................i

IM 12B03D02-01E 1-1
1.Outline
1. Outline
The Model PH72 Personal pH/ORP Meter is a highly accurate, portable pH meter for
laboratory and eld application. With its self-diagnostic function, the PH72 provides
precise measurement of pH and ORP (oxidation-reduction potential). Measurement
results can be stored and stored data can be checked on the meter display any time.
The PH72 meter is of waterproof construction so that it can safely be used outdoors
on a rainy day, and can also withstand being accidentally dropped into water. With
its waterproof construction, the PH72 can be used outdoors in any weather and will
not be damaged if it accidentally falls into water (tap water, etc.). However, since
the PH72 is not hermetically sealed, do not leave it in water for a long time or pour
chemical solutions on it.
1.1 Features
Water resistant case
When this meter is used with its dedicated sensor, it meets the requirements of class
IP67 according to “Degree of Protection Provided by Enclosure” in IEC 60529.
Simple calibration
Automatic calibration based on preprogrammed data of standard solutions or manual
calibration can be done through simple key operations.
Calendar and clock function
Internal clock functions allow “one-touch checking” of measurement date and time.
Data storage function
Up to 300 measured pH values along with their respective solution temperatures,
dates and times, can be stored and stored data can be checked on the display any
time.
Auto power o󰀨 function
The meter will turn o󰀨 power automatically if not operated during a preset time period.
The auto power o󰀨 time can be user congurable in the range of 1 to 120 minutes in
increments of 1 minute. The auto power o󰀨 function can be disabled, where the meter
should be used with care to conserve the batteries.
Alarm clock function
The meter can issue an alarm signal at a specied time. Even when meter power is
turned o󰀨, the internal clock can issue an alarm signal.
Self-diagnostic function
A relevant error message will appear based on the self-diagnostic function.
Large, clear LCD
A measured pH (mV) value, solution temperature, date and time are clearly viewed on
the display.
Compact, lightweight, and handy
The meter ts comfortably your hand and also stands rm on the table.

IM 12B03D02-01E
1-2
1.Outline
1.2 Specications
Measurement: Hydrogen ion concentration (pH) or oxidation-reduction
potential (ORP) of solution
Measuring range: pH; 0 to 14 pH*1
ORP: -2000 to 2000 mV
Temperature; 0 to 80°C*2(or 0 to 100°C*4)
Resolution: pH; 0.01 pH
ORP: 1 mV (0.1 mV: -199.9 to 199.9 mV)
Temperature; 0.1°C
Repeatability (without sensor): pH; ±0.01 pH
ORP: ±1 mV
Accuracy: Temperature; ±0.7°C (0 to 70°C)
±1°C (above 70°C)
Display: Digital LCD
Indication: pH or ORP (mV) and solution temperature (simultaneously),
sensor check, various messages *3
Temperature compensation (glass electrode emf — temperature characteristics):
Automatic compensation (or manual compensation*4)
Solution temperature: 0 to 80°C (or 0 to 100°C*4) (0 to 50°C when a KCl replenish-
free type sensor and its sensor cable are immersed in water)
Solution conductivity: 50 μS/cm or more *5
Calibration: Automatic (1 or 2 point), manual
Ambient temperature: 0 to 50°C
Wetted Material: ●KCl replenish-free type combination pH sensor
Polypropylene resin (sensor body, protective
cover), Glass (glass electrode, temperature sensor
protection tube), Ceramics (liquid junction), Silicon
rubber (sensor seal)
●KCl rellable type combination pH sensor
PVC (cable), rigid polyethylene (grip), ethylene
propylene rubber (grip and cable connection),
Polypropylene resin (sensor body, protective
cover), Glass (glass electrode, temperature sensor
protection tube), Ceramics (liquid junction), Silicon
rubber (sensor seal)
●Needle type pH sensor
Glass (sensor body)
●Test tube size pH sensor
Glass (sensor body)
●KCl rellable type ORP sensor
Platinum (electrode), Polypropylene resin (sensor
body, protective cover), Glass (glass electrode,
temperature sensor protection tube), Ceramics
(liquid junction), Silicon rubber (sensor seal)
Construction: Protection class IP67 (IEC 60529)
Dimensions: Approximately 150(H) x 61(W) x 42(D) mm (not including
connector part)
Weight: Approximately 220 g (without sensor)

IM 12B03D02-01E 1-3
1.Outline
Power source: 2x AA batteries (LR6)
Auto power o󰀨 function (time congurable: 1 to 120 minutes)
Battery life: Approximately 600 hours*6of continuous use (battery type
and operating condition dependent)
Functions: Data memory (300 points), alarm clock, etc.
EMC Compliance:
EMI (Emission): EN 61326-1 Class B
Test Item Frequency Range Basic Standard
Electromagnetic radiation disturbance 30 to 1000 MHz CISPR 16-1 and 16-2
EMS (Immunity): EN 61326-1 Table 2 (For ise in industrial locations *7)
No. Test Item Test Specication Basic Standard Performance
Criteria*
1Electrostatic
discharge
4 kV (contact)
8 kV (air) IEC 61000-4-2 A
2
RF amplitude
modulated
electromagnetic eld
80 to 1000 MHz,
10 V/m (unmodulated)
80% AM (1 kHz)
IEC 61000-4-3
B**
1.4 to 2.0 GHz,
10 V/m (unmodulated)
80% AM (1 kHz)
A
2.0 to 4.0 GHz,
3 V/m (unmodulated)
80% AM (1 kHz)
A
* A: Normal performance within the specication limits: ±20% of the measured value.
B: Temporary degration or less of function or performance which is self-recoverable.
** Display value may be a󰀨ected by strong electromagnetic eld.
EMC Regulatory Arrangement in Australia and New Zealand (RCM)
EN 61326-1 Class B, Table2
Korea Electromagnetic Conformity Standard Class B 한국 전자파적합성 기준
B급 기기 (가정용 방송통신기자재)
이 기기는 가정용(B급) 전자파적합기기로서
주로 가정에서 사용하는 것을 목적으로 하며,
모든 지역에서 사용할 수 있습니다.
Environmental resistance:
Compliant with RoHS*8, WEEE, and EU battery directive
*1: Display range is from -2 to 10 pH.
*2: Display range is from-10 to 120°C. When a needle type or test tube size pH sensor is used. 0
to 50ºC when a KCl replenish-free type sensor and its sensor cable are immersed in water.
*3: When needle type or test tube size pH sensor is connected, liquid temperature can not be
measured.
*4: When a needle type or test tube size pH sensor is connected.
*5: Conrm that the solution conductivity is 50 μS/cm or more.
*6: When alkaline batteries are used.
*7: Display value may be a󰀨ected by strong electromagnetic eld.
*8: RoHS: EN IEC 63000 (Style 2.03 and later)

IM 12B03D02-01E
1-4
1.Outline
1.3 When You Receive the PH72 Meter Package
Conrm that you received all package components of the PH72 meter you ordered
referring to the Model and Su󰀩x Code and the item list in Section 1.4, “PH72 Meter
Kit.” Carefully inspect the meter and sensor, referring to Section 1.5, “PH72 Meter
— Part Names and Functions” and Section 1.6, “Sensors — Types, Part Names and
Functions.” Particular attention should be taken:
• Not to lose a wetting cap attached on the sensor tip. This cap is needed for
storage
• Not to twist or pull the cable
• Not to hit or drop the meter
• Not to get connectors dirty
• In handling of standard solutions and reagents
Solution bottles should be stored in a cool, dark place and tightly capped after
use. Once opened, the contents of a bottle should be used early. Dispose of
solutions in accordance with local regulations.

IM 12B03D02-01E 1-5
1.Outline
1.4 PH72 Meter Kit
PH4 PH7
KCl
12 13
15
14
16
11
67 10
89
1
5
4
3
2
Quick Manual
Note: On the name plate of sensor, Model and Suffix Code of sensor itself (PH72SN- -AA or
OR72SN- -AA) is indicated. (See Section 1.6.)
*1: PH72-60 and PH72-61 comform to the Japanese Measurement Act. CE marking is not attached.
Its hardware is the same as “PH72-00” or “PH72-21” respectively.
*2: In South Korea and Malaysia, primary battery is limited by regulations.
Prepare batteries with the authorized certification mark for each country.
Personal pH/ORP meter
Without sensor
With KCl replenish-free type combination pH sensor (cable length: 0.75 m)
With KCl replenish-free type combination pH sensor (cable length: 3 m)
With KCl refillable type combination pH sensor (cable length: 0.75 m)
With KCl refillable type combination pH sensor (cable length: 3 m)
With needle type pH sensor (cable length: 0.75 m)
With test tube size pH sensor (cable length: 0.75 m)
With KCl refillable type ORP sensor (cable length: 0.75 m)
With KCl refillable type ORP sensor (cable length: 3 m)
With KCl refillable type combination pH sensor (cable length:
0.75 m) + KCl refillable type ORP sensor (cable length: 0.75 m)
Meter pnly, without sensor *1
With KCl refillable type combination pH sensor (cable length: 0.75 m) *1
Japanese
English
Global except South Korea and Malaysia (with batteries)
South Korea and Malaysia (without batteries) *2
PH72
Connecting -00
sensors -11
-13
-21
-23
-32
-33
-41
-43
-51
-60
-61
Language -J
-E
Country -AA
-NB
Specification
1 to 4 in common, plus:
None
6, 11, 12, 13, 14
6, 11, 12, 13, 14
7, 11, 12, 13, 14, 15, 16
7, 11, 12, 13, 14, 15, 16
8, 11, 12, 13, 14, 15, 16
9, 11, 12, 13, 14, 15, 16
10, 11, 15, 16
10, 11, 15, 16
7, 10, 11, 12, 13, 14, 15,
16
None
7, 11, 12, 13, 14, 15, 16
5
None
Items Included
Model Suffix Code
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
No.
Personal pH/ORP meter
User's Manual and Quick Manual
Non-slip pads (2 pcs)
Hand strap
Dry batteries, 2x AA batteries
KCl replenish-free type pH sensor
KCl refillable type pH sensor
Needle type pH sensor
Test tube size pH sensor
KCl refillable type ORP sensor
Cotton swabs for sensor cleaning
pH 4 standard solution (50 mL)
pH 7 standard solution (50 mL)
Calibration bottles (2 bottles)
3.3 M KCl solution (50 mL)
Syringe (5 mL)
Item
F010401.ai

IM 12B03D02-01E
1-6
1.Outline
1.5 PH72 Meter — Part Names and Functions
2014.
S2.0
E000001
Sensor cable connector
Display
Keypad
O-ring
Connection to a dedicated
pH (ORP) sensor.
pH (mV) and temperature
simultaneously.
Hand strap
attachment points
Name plate
Battery box cover fixing screw
F010501.ai
1.6 Sensors — Types, Part Names and Functions
Sensors available for use with the Model PH71 Personal pH Meter are: general-
purpose pH sensors (KCl replenish-free and KCl rellable types), needle type pH
sensor, and test tube size pH sensor. Check the Model and Su󰀩x Code on the name
plate to identify the type of your sensor.

IM 12B03D02-01E 1-7
1.Outline
pH sensor for Personal pH/ORP meter
KCl replenish-free type combination pH sensor (cable length: 0.75 m)
KCl replenish-free type combination pH sensor (cable length: 3 m)
KCl replenish-free type combination pH sensor (cable length: 0.75 m)
KCl replenish-free type combination pH sensor (cable length: 3 m)
KCl refillable type combination pH sensor (cable length: 0.75 m)
KCl refillable type combination pH sensor (cable length: 3 m)
KCl refillable type combination pH sensor (cable length: 0.75 m)
Needle type pH sensor (cable length: 0.75 m)
Test tube size pH sensor (cable length: 0.75 m)
Needle type pH sensor (cable length: 0.75 m)
Test tube size pH sensor (cable length: 0.75 m)
KCl refillable type combination pH sensor (cable length: 0.75 m)
Always -AA
*1: Part number of PH81, PH82 (previous models).
*2: pH sensor for PH81, PH82 (previous models). Waterproofing is not guaranteed
if you use PH82-type sensor in conjunction with PH72 meter.
PH72SN
Type -11
-13
-18
-19
-21
-23
-28
-32
-33
-38
-39
-61
—-AA
Specification
K9220YA
K9220YB
K9220YC
K9220YG
K9220YJ
RemarksModel Suffix Code
Example of Name Plate
Model and Suffix Code for pH and ORP Sensors
F010601.ai
*1
*1
*2
*2
*2
*2
*2
*2
ORP sensor for Personal pH/ORP meter
KCl refillable type ORP sensor (cable length: 0.75 m)
KCl refillable type ORP sensor (cable length: 3 m)
KCl refillable type ORP sensor (cable length: 0.75 m)
KCl refillable type ORP sensor (cable length: 3 m)
Always -AA
OR72SN
Type -41
-43
-48
-49
—-AA
Specification
K9220YL
RemarksModel Suffix Code
*2
S2.0
000001-11-AA
STYLE
Made in Japan
MODEL
SUFFIX NO.
PH72SN
F010602.ai
KCl replenish-free type combination pH sensor
Sensor body
Sensor grip
Sensor grip
Fill hole for KCl filling solution
Fill hole plug
Glass electrode
(Platinum electrode)
Glass electrode
Sensor cable
Waterproof cover
Connector
Name plate
KCl refillable type combination pH sensor,
ORP sensor
Wetting cap
Wetting cap
Sensor body
Sensor cable
Waterproof
cover
Connector
Name plate
Protective cover
Liquid
junction
Temperature element
Liquid junction
Temperature element
Prevents water ingress
that may cause
insulation failure.
Measures pH
values.
Removed only
during cleaning. Measures solution temperature
and compensates for temperature
effect on pH electrode.
Used to prevent glass electrode from dying out. During storage this cap
with cotton wad moistened with water should be attached to electrode tip.
Connection to pH/ORP
meter.
Plastic body that can withstand
temperature up to 80C.
Provides electrical contact
between internal reference
electrode and sample solution.
3.3 mol/L KCl solution is used.
Prevents filling solution from
leaking from fill hole during
storage. Always unplugged
during measurement.
Protective cover
*1
*1
*1
PH72 - 21 - - AA
PH72 - 23 - - AA
PH72 - 11 - - AA
PH72 - 13 - - AA
PH72 - 41 - - AA
PH72 - 43 - - AA
PH72 - 51 - - AA
( PH72SN-11-AA,
PH72SN-13-AA )
*1
( PH72SN-21-AA,
PH72SN-23-AA,
OR72SN-41-AA,
OR72SN-43-AA )
*1: On the name plate of sensor, Model and Suffix Code of sensor itself (PH72SN- -AA or OR72SN- -AA) is indicated. (See Section 1.6.)

IM 12B03D02-01E
1-8
1.Outline
1.7 Spare Parts
O-ring and gasket set
(Part no. : K9654AY)
2 gaskets for battery box
2 O-rings for connector
Cap set
(Part no. : K9220ZY)
Used for sensor.
1 protective cover
1 wetting cap F010801.ai
pH 9 Standard solution
(Part no. : K9084KH) *
pH 7 Standard solution
(Part no. : K9084KG) *
pH 4 Standard solution
(Part no. : K9084KF) *
Used for calibration (250 mL). Used for calibration (250 mL). Used for calibration (250 mL).
Calibration bottle
(Part no. : K9220WW)
Quinhydrone reagent for ORP Check
(Part no. : K9024EC)
3.3 M KCl solution
(Part no. : K9220XH)
Used during calibration. 2 x
10-mL bottles.
Used to replenish KCl refillable
type sensor. 3.3 mol/L, 2 bottles
x 50 mL
Used to check ORP electrode. 3
packs, one pack for 250 mL
solution.
* Safety data sheet (SDS)
https://www.yokogawa.com/library/
O-rings and gaskets are important parts to ensure that the PH72 meter is water
resistant. Replace these parts as required. Refer to Section 6.8, “Storage and O-ring/
Gasket Replacement” for replacement.

IM 12B03D02-01E 2-1
2.Preparation
2. Preparation
2.1 Installing the Batteries
Install the batteries rst.
In South Korea and Malaysia, primary battery is limited by regulations.
Please use batteries with the authorized certication mark for each country.
CAUTION
Select a relatively moisture-free location when installing batteries in the meter.
When installing batteries, observe correct polarity (battery orientation). Failure to do
so may damage to the meter.
Remove batteries from the meter if it is to be stored for an extended period of time.
Do not leave dead batteries in the meter. They may leak and cause meter failure or
erratic operation of the meter.
When replacing batteries, replace both batteries at the same time. If only one battery
is replaced, which may leak chemicals and damage the meter.
If the battery box gasket is damaged or dirty then the unit may no longer be
waterproof; replace the gasket in this case.
(1) Loosen the screw holding the battery
box cover using a coin or similar object.
(2) Remove the battery box cover, and
then install the batteries observing
polarity diagram inside.
(3) Make sure the gasket on the inside
rim of the battery box is free of foreign
material.
(4) Put the cover back on. Insert the tabs
on the top of the cover into the slots at
an angle of at least 45° and lower the
cover into position.
(5) Hold both sides of the cover down rmly
and fasten the screw with a coin or
similar object.
Tighten the screw in a vertical direction.
The head of the screw does not align
with the cover. If you feel resistance,
stop tightening, loosen the screw, and
then try to retighten it. A small gap
should remain between the cover and
the body even after tightening (due to
a gasket).
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Gasket
Allowable gap
Batteries
Hold down
firmly
45° or more

IM 12B03D02-01E
2-2
2.Preparation
2.2 Connecting the Sensor Cable
Connect the sensor cable.
CAUTION
Connect the sensor cable in a place free from moisture.
When connecting the sensor cable, tighten by turning only the silver locknut, do
not turn the cable or waterproof cover. Also take care not wet or contaminate the
connector.
Sensors for the PH81 or PH82 meters can be connected. When used in conjunction
with the PH72 meter, however, water resistance is not guaranteed. This is due to the
di󰀨erent construction of the connector cover.
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O-ring
(1) Pull the waterproof cover along
the sensor cable away from the
connector to expose the locknut.
(2) Connect the connector to the
meter body*. Then tighten firmly
by turning only the locknut.
* Align the slots of the sensor cable
connector with the posts of the
connector on the meter.
(3) Move the waterproof cover
toward the connector until it
contacts with the O-ring* on the
meter body.
* Make sure that the O-ring is free of
foreign material.
(4) Push and rotate the waterproof
cover 1/4 turn (90 degrees)
clockwise to lock into place.
Locknut
(Silver)
Waterproof cover
(1)
(2)
(4)
(3)
Note: It is recommended that the sensor be kept connected to the meter to avoid
contamination of the connectors.
2.3 Setting the Date and Time
After installing the batteries, set the date and time. Note that if the power is turned
o󰀨 before completing minute setting, start with the date setting when you turn on the
power next time. By replacing the batteries, the date setting is not a󰀨ected but the
time setting is. So the time must be reset.
Note: If a sensor cable is not connected to the meter, uctuating readings or an error message
may appear. Before pressing POWER key, make sure that a sensor has been
connected.

IM 12B03D02-01E 2-3
2.Preparation
lSetting Procedure
After installing the batteries, press and hold POWER key for at least one second.
All LCD segments appears momentarily and then the date setting display starts
automatically. Set year, month, day, hours, and minutes following the owchart below.
Note: If you attempt to abort the setting procedure before completing, the meter will beep three
times and reject the attempt. Continue until the minute setting is completed.
F020301.ai
for at least 1 sec.
Press
to set
to confirm
to set
to set
to confirm
to confirm
to set
to confirm
Year setting
Day setting Hour setting (24-hour format)
Month setting
Minute setting
After
several
seconds
After
several
seconds
POWER
F/ENT
F/ENT F/ENT
F/ENT
to set to confirm
or
F/ENT
2.4 Selecting pH or ORP Measurement
Upon completing the date and time setting, the meter is ready for pH measurement.
The display shows a pH value with a “pH” unit to the left of the value.
To use the meter for ORP measurement, make sure that an ORP sensor is connected
to the meter. Then, change the display for ORP measurement following the procedure
described in Section 5.3 (3), “Set measurement unit (PV.U) panel.” The display should
show a “mV” unit at the lower right beneath a value when the meter is ready for ORP
measurement.

IM 12B03D02-01E
2-4
2.Preparation
2.5 Wetting Cap
The glass electrode should be kept wet during storage. If the glass electrode dries
out, it will take hours to rehydrate and in the meantime the meter may give erroneous
readings. The wetting cap is used to prevent the glass electrode from drying out.
Sensors are shipped with a wetting cap containing a cotton wad moistened with a few
drops of water. For storage replenish the cap with a few drops of water (tap water)
and attach to the sensor rmly.
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Protective cover
Lug
Slot
To remove cap, rotate counterclockwise
and pull out until lugs on cap clear
protective cover through slots.
Removed cap can be
attached onto sensor cable
during measurement.
Figure 2.1 Wetting Cap
2.6 Manual Temperature Setting
If a sensor without a built-in temperature element (needle type or test tube size pH
sensor) is connected to the meter, mark will appear on the display. In this
case, measure the temperature of the solution being measured and manually set the
measured temperature into the PH72 meter for reliable measurement. The procedure
is described in Section 5.3 (2), “Manual temperature setting (M.tP) panel.”
Temperature compensation is performed based on a temperature shown on the
display of the PH72 meter. If a temperature shown on the display is di󰀨erent from the
actual temperature of the sample being measured, the displayed measured value
may not be true. The bigger the di󰀨erence between the temperature displayed on the
meter and the actual temperature of the solution, the bigger the error between the
displayed measured value and the true value.
If mark appears on the display even though a sensor with a built-in
temperature element is connected, refer to Section 7.4.
2.7 pH Calibration
The PH72 meter needs to be calibrated:
• when the sensor is connected for the rst time;
• after the sensor is replaced;
• after the meter has been stored for a long period;
• after the electrode is cleaned; or
• when necessary.
The calibration procedure is described in Chapter 4, “Calibration.”
Note: Calibration results are saved in the meter when the batteries are replaced.

IM 12B03D02-01E 3-1
3.Measurement
3. Measurement
3.1 Precautions
(1) After storage for an extended period of time, it is recommended that the meter
should be calibrated before taking measurements.
(2) When using a KCl rellable type sensor, check the level of lling solution (refer to
Section 6.6).
(3) Do not use the meter in a solution with the temperature exceeding 80°C (100°C
for the needle type and test tube size pH sensors). When a KCl replenish-free
type sensor is used and its sensor grip is immersed, the temperature of the
solution should not exceed 50°C. Also, do not use the meter in strongly corrosive
solutions, such as a solution containing hydrouoric acid.
(4) Remove stains from the PH72 meter body using a soft cloth or tissue. If
necessary, use a neutral detergent.
(5) If an abnormal symptom occurs during measurement, locate the cause of the
problem and take corrective actions referring to Chapter 7, “Troubleshooting.”
(6) After measurement, rinse o󰀨 dirt or the sample solution from the sensor with
water and store it (refer to Chapter 6, “Maintenance”).
(7) Keys should be operated by ngers.
Using the PH72 Meter on a Table
The meter is designed as a portable instrument; however, to use it on a table, attach
non-slip pads (supplied with the instrument) at top and bottom of the meter to stop it
from moving when the sensor is moved.
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Non-slip pads
Figure 3.1 Position of Non-slip Seats