Yokogawa PH72 User Manual

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User’s Manual

Model PH72 Personal pH/ORP Meter

IM 12B03D02-01E

3rd Edition

Preface

Thank you for purchasing the Model PH72 Personal pH/ORP Meter. Please read this manual thoroughly before using the meter.

The following symbol marks are used for safety precautions in this manual.

Preface

WARNING

CAUTION

: Indicates that serious injury may result, if the user fails to

follow instructions.

: 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-specifications use of the product; Use in an unsuitable environment; Repair or modification of this or related products by persons other than Yokogawa-

authorized engineers.

Preface

Liquid Crystal Display (LCD) Characters

On the LCD alphanumeric characters are displayed as follows.

Alphabet

Display

Alphabet

Display DisplayNumerals

All display segments

Note 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.

Flashing Displays

Flashing messages, numbers and digits on the display are indicated in gray in this manual.

F00.EPS

Flashing state: Lit state:

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Warranty 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 offer different 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 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 fluids must be decontaminated / disinfected before shipment, and a statement to this effect should be included. Safety data sheets for all process components that the goods have exposed to should also be included.

Preface

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Contents

CONTENTS

Preface...................................................................................................................... 1-1

1. Outline ................................................................................................................. 1-1

1.1 Features ......................................................................................................................... 1-1

1.2 Specifications ................................................................................................................. 1-2

1.3 When You Receive the PH72 Meter Package .............................................................. 1-3

1.4 PH72 Meter Kit .............................................................................................................. 1-4

1.5 PH72 Meter — Part Names and Functions .................................................................. 1-5

1.6 Sensors — Types, Part Names and Functions............................................................. 1-6

1.7 Options (Available Separately) ...................................................................................... 1-8

1.8 Spare Parts .................................................................................................................... 1-9

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 ............................................................................................ 2-3

2.4 Selecting pH or ORP Measurement .............................................................................. 2-4

2.5 Wetting Cap ................................................................................................................... 2-4

2.6 Manual Temperature Setting ......................................................................................... 2-5

2.7 pH Calibration ................................................................................................................ 2-5

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..................................................................................................... 4-3

4.2 Manual Calibration ......................................................................................................... 4-6

5. Keypad and Display Functions ......................................................................... 5-1

5.1 Keypad Functions .......................................................................................................... 5-2

5.2 Display Items ................................................................................................................. 5-4

5.3 Function Mode ............................................................................................................... 5-5

6. Maintenance ........................................................................................................ 6-1

6.1 For Optimum Meter Performance.................................................................................. 6-1

6.2 pH Electrode Cleaning................................................................................................... 6-2

6.3 Sensor Replacement ..................................................................................................... 6-3

6.4 Rehydrating the Glass Electrode................................................................................... 6-3

6.5 Replenishing the Electrode with Filling Solution (KCl solution) .................................... 6-4

6.6 Cleaning and Drying Connectors .................................................................................. 6-5

6.7 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 ............................................................................................................ 7-6

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 ............................................................................................ 8-3

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

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Contents

9.3 Temperature Compensation .......................................................................................... 9-4

9.4 The Asymmetry Potential .............................................................................................. 9-5

9.5 The Alkaline Error .......................................................................................................... 9-6

9.6 The Acid Error ............................................................................................................... 9-7

9.7 Calibration Calculation ................................................................................................... 9-8

9.8 ORP (Oxidation-Reduction Potential) ............................................................................ 9-9

9.9 Reference Electrode .................................................................................................... 9-10

9.10 Wetted Part Materials of Sensors ............................................................................. 9-12

9.11 References................................................................................................................. 9-12

Appendix ..................................................................................................................... 1

MSDS (Material Safety Data Sheet) ............................................................... MADS-1

Revision Record .......................................................................................................... i

IM 12B03D02-01E

Contents

IM 12B03D02-01E

1. Outline

The Model PH72 Personal pH/ORP Meter is a highly accurate, portable pH meter for laboratory and field 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.

1.1 Features

Water r esistant 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 off function

The meter will turn off power automatically if not operated during a preset time period. The auto power off time can be user configurable in the range of 1 to 120 minutes in increments of 1 minute. The auto power off 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 specified time. Even when meter power is turned off, 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 fits comfortably your hand and also stands firm on the table.

1. Outline

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1-1

1. Outline

1.2 Specifications

Measuring range: pH: 0 to 14 pH*

ORP: -2000 to 2000 mV Temperature: 0 to 1008C*

Resolution: pH: 0.01 pH

ORP: 0.1 mV (-199.9 to 199.9 mV)

1 mV (-2000 to -200 mV and 200 to 2000 mV)

Temperature: 0.18C

Repeatability (without sensor): pH: 60.01 pH 61 digit

ORP: 61 mV 61 digit

Accuracy (Temperature): 60.78C (0 to 708C)

618C (above 708C)

Temperature compensation (glass electrode emf — temperature characteristics):

Automatic compensation (or manual compensation*1)

Solution temperature: 0 to 808C (or 0 to 1008C*3) (0 to 508C when a KCl replenish-

free type sensor and its sensor cable are immersed in water) Solution conductivity: 50 mS/cm or more Ambient temperature: 0 to 508C Construction: Protection class IP67 (IEC 60529) Power source: 2x AA batteries (LR6)

Auto power off function (time configurable: 1 to 120 minutes) Battery life: Approximately 600 hours*4 of continuous use (battery type and

operating condition dependent) Dimensions: Approximately 150(H) x 61(W) x 42(D) mm (not including

connector part) Weight: Approximately 220 g (including batteries) EMC Conformity Standards: EMI (Emission) EN 61326-1 Class B

Test Item

Electromagnetic radiation disturbance

EMS (Immunity) EN 61326-1 Table 2 (For use in inductrial locations)

Test ItemNo.

Electrostatic

discharge

RF amplitude

modulated electromagnetic field

* A: Normal performance within the specification limits: ±20% of the measured value. B: Temporary degration or less of function or performance which is self-recoverable. ** Display value may be affected by strong electromagnetic field.

Test Specification Basic Standard

4 kV (contact) 8 kV (air)

80 to 1000 MHz, 10 V/m (unmodulated) 80% AM (1 kHz)

1.4 to 2.0 GHz, 10 V/m (unmodulated)

80% AM (1 kHz)

2.0 to 4.0 GHz,

3 V/m (unmodulated) 80% AM (1 kHz)

*1: Display range is from -2 to 10 pH. *2: Display range is from-10 to 1208C. *3: When a needle type or test tube size pH sensor is used. *4: When alkaline batteries are used.

1-2

Frequency Range

30 to 1000 MHz

IEC 61000-4-2

IEC 61000-4-3

CISPR 16-1 and 16-2

Basic Standard

T0101.EPS

Performance

Criteria*

B**

T0102.EPS

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1.3 When You Receive the PH72 Meter Package

Confirm that you received all package components of the PH72 meter you ordered referring to the Model and Suffix 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.

1. Outline

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1-3

1. Outline

1.4 PH72 Meter Kit

8 11

Instrument Card

Quick Manual

No.

Item

Personal pH/ORP meter

Dry batteries, 2x AA batteries

User's Manual and Quick Manual

Non-slip pads (2 pcs)

Hand strap

Instrument Card

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)

KCl filling solution (3.3 mol/l, 50 ml)

Syringe (5 ml)

13 14

PH4

PH7

KCl

1-4

Model Suffix Code

PH72

Sensors -00

-11

-13

-21

-23

-32

-33

-41

-43

-51

Label -J language -E

- -AA 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.)

Specification

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) Japanese English

Always -AA

Items Included

1 to 6 in common, plus: None

7, 12, 13, 14, 15 7, 12, 13, 14, 15

8, 12, 13, 14, 15, 16, 17 8, 12, 13, 14, 15, 16, 17

9, 12, 13, 14, 15, 16, 17 10, 12, 13, 14, 15, 16, 17 11, 12, 16, 17 11, 12, 16, 17 8, 11, 12, 13, 14, 15, 16, 17

F010401.EPS

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1.5 PH72 Meter — Part Names and Functions

1. Outline

O-ring

Sensor cable connector

Connection to a dedicated pH (ORP) sensor.

Hand strap attachment points

Display

pH (mV) and temperature

simultaneously.

Keypad

PERSONAL

pH/ORP METER

PH72

MODEL

S1.0

STYLE No.

E000001

2004.

Battery box cover fixing screw

Name plate

F010501.EPS

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1-5

1. Outline

1.6 Sensors — Types, Part Names and Functions

Sensors available for use with the Model PH72 Personal pH/ORP Meter are: generalpurpose pH sensors (KCl replenish-free and KCl refillable types), needle type pH sensor, test tube size pH sensor, and KCl refillable type ORP sensor. Check the Model and Suffix Code on the name plate to identify the type of your sensor.

Example of Name Plate

STYLE

MODEL

PH72SN

SUFFIX NO.

Model and Suffix Code for pH and ORP Sensors

Specification

PH72SN

-11

-13

-18

-19

-21

-23

-28

-32

-33

-38

-39

-AA

Model Suffix Code

OR72SN

-41

-43

-48

-49

-AA

: Part number of PH81, PH82 (previous models).

: Waterproofing is not guaranteed if you use PH82-type sensor in conjunction with PH72 meter.

pH sensor for Personal pH/ORP meter

For PH71, PH72; KCl replenish-free type combination pH sensor (cable length: 0.75 m) For PH71, PH72; KCl replenish-free type combination pH sensor (cable length: 3 m) For PH81, PH82; KCl replenish-free type combination pH sensor (cable length: 0.75 m) For PH81, PH82; KCl replenish-free type combination pH sensor (cable length: 3 m)

For PH71, PH72; KCl refillable type combination pH sensor (cable length: 0.75 m) For PH71, PH72; KCl refillable type combination pH sensor (cable length: 3 m) For PH81, PH82; KCl refillable type combination pH sensor (cable length: 0.75 m)

For PH71, PH72; needle type pH sensor (cable length: 0.75 m) For PH71, PH72; test tube size pH sensor (cable length: 0.75 m) For PH82; needle type pH sensor (cable length: 0.75 m) For PH82; test tube size pH sensor (cable length: 0.75 m) Always -AA

Specification ORP sensor for Personal pH/ORP meter

For PH72; KCl refillable type ORP sensor (cable length: 0.75 m) For PH72; KCl refillable type ORP sensor (cable length: 3 m) For PH82; KCl refillable type ORP sensor (cable length: 0.75 m) For PH82; KCl refillable type ORP sensor (cable length: 3 m) Always -AA

S1.0

000001-11-AA

Made in Japan

RemarksModel Suffix Code

K9220YA

K9220YB

K9220YC

K9220YG

K9220YJ

Remarks

K9220YL

F010601.EPS

1-6

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KCl replenish-free type combination pH sensor

PH72 - 11 - - AA PH72 - 13 - - AA

Name plate

( PH72SN-11-AA, PH72SN-13-AA )

Waterproof cover

Prevents water ingress that may cause insulation failure.

Connector

Connection to pH/ORP meter.

Glass electrode

Measures pH

values.

Protective cover

Removed only during cleaning.

Liquid junction

Provides electrical contact between internal reference electrode and sample solution.

Temperature element

Wetting cap

Used to prevent glass electrode from dying out. During storage this cap

*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.)

with cotton wad moistened with water should be attached to electrode tip.

Sensor cable

Sensor body

Plastic body that can withstand temperature up to 80°C.

Glass electrode

(Platinum electrode)

KCl refillable type combination pH sensor, ORP sensor

PH72 - 21 - - AA PH72 - 23 - - AA PH72 - 41 - - AA

Name plate

( PH72SN-21-AA, PH72SN-23-AA, OR72SN-41-AA, OR72SN-43-AA )

Connector Sensor grip

Wetting cap

Sensor body

Temperature element

Protective cover

PH72 - 43 - - AA PH72 - 51 - - AA

Waterproof cover

Fill hole plug

Liquid junction

Fill hole for KCl filling solution

Measures solution temperature and compensates for temperature effect on pH electrode.

3.3 mol/l KCl solution is used.

Sensor cable

Sensor grip

Prevents filling solution from

leaking from fill hole during storage. Always unplugged during measurement.

1. Outline

F010602.EPS

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1-7

1. Outline

1.7 Options (Available Separately)

The following options are available for the Model PH72 Personal pH/ORP Meter for your convenience. When ordering, specify the part number.

pH 9 Standard solution

(Part no. : K9220XF)

Used for calibration when anticipated pH value of sample solution is alkaline. (50ml)

Soft carrying case

(Part no. : B9269KJ)

Unit: mm

Approx. 280

Approx. 140

A soft black carrying case holds

pH/ORP meter and sensor.

Approx. 30

Sensor stand

(Part no. : K9220XN)

Holds a sensor when pH/ORP meter is used on the table. Made of rustproof stainless

steel.

F010 701 .EPS

1-8

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1.8 Spare Parts

1. Outline

pH 4 Standard solution

(Part no. : K9084KF)

Used for calibration. (250 ml)

KCl solution

(Part no. : K9220XH)

Used to replenish KCl refillable type sensor. 3.3 mol/l, 2 bottles x 50 ml

pH 7 Standard solution

(Part no. : K9084KG)

Used for calibration. (250 ml)

Quinhydrone reagent (Part no. : K9024EC)

Used to check ORP electrode. 3 packs, one pack for 250 ml solution.

pH 9 Standard solution

(Part no. : K9084KH)

Used for calibration. (250 ml)

Calibration bottle

(Part no. : K9220WW)

Used during calibration. 2 10-ml bottles.

2 gaskets for battery box 2 O-rings for connector

IM 12B03D02-01E

O-ring and gasket set

(Part no. : K9654AY)

Cap set

(Part no. : K9220ZY)

Used for sensor. 1 protective cover 1 wetting cap

F010801.EPS

1-9

1. Outline

O-rings and gaskets are important parts to ensure that the PH72 meter is water resistant. Replace these parts as required. Refer to Section 6.7, “Storage and O-ring/Gasket Replacement” for replacement.

1-10

IM 12B03D02-01E

2. Preparation

2.1 Installing the Batteries

Install the batteries first.

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, the new battery may discharge into the old battery, 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

458 or more

Batteries

Gasket

Press with your fingers

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 458 and lower the cover into position.

(5) Press the both ends of the cover down

with your fingers and tighten the screw to fix the cover onto the unit using a coin or similar object.

Note: Do not attempt to tighten further

when you feel resistance before the cover is fastened in place. Loosen the screw once and retighten.

2. Preparation

IM 12B03D02-01E

F020101.eps

2-1

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 different construction of the connector cover.

(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.

(2)

Waterproof cover

O-ring

(3)

Locknut (Silver)

(1)

(4)

F020201.eps

Note: It is recommended that the sensor be kept connected to the meter to avoid

contamination of the connectors.

2-2

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2.3 Setting the Date and Time

After installing the batteries, set the date and time. Note that if the power is turned off 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 affected but the time setting is. So the time must be reset.

Note: If a sensor cable is not connected to the meter, fluctuating readings or an error

message may appear. Before pressing been connected.

• Setting Procedure

After installing the batteries, press and hold LCD segments appears momentarily and then the date setting display starts

automatically. Set year, month, day, hours, and minutes following the flowchart 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.

POWER

Press

for at least 1 sec.

POWER

key, make sure that a sensor has

POWER

key for at least one second. All

2. Preparation

Day setting Hour setting (24-hour format)

IM 12B03D02-01E

Year setting

After several seconds

F/ENT

to set

F/ENT F/ENT

to confirm

F/ENT

to set

After several seconds

F/ENT

to confirm

Month setting

to set

Minute setting

to set

F020301.EPS

2-3

2. Preparation

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.

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 firmly.

Protective cover

Lug

Slot

Figure 2.1 Wetting Cap

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.

F0201.EPS

2-4

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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 different from the actual temperature of the sample being measured, the displayed measured value may not be true. The bigger the difference 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 first 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.

2. Preparation

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2-5

2. Preparation

2-6

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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 refillable type sensor, check the level of filling solution. (Refer

to Section 6.5.)

(3) Do not use the meter in a solution with the temperature exceeding 808C (1008C 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 508C. Also, do not use the meter in strongly corrosive solutions, such as a solution containing hydrofluoric 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 off dirt or the sample solution from the sensor with water

and store it. (Refer to Chapter 6, “Maintenance.”)

(7) Keys should be operated by fingers.

Using the PH72 Meter on a Table

The meter is designed as a portable instrument; however, to use it on a table, attach nonslip pads (supplied with the instrument) at top and bottom of the meter to stop it from moving when the sensor is moved.

3. Measurement

IM 12B03D02-01E

Non-slip pads

PERSONAL

pH/ORP METER

MODEL

PH72

STYLE

S1.0

No.

E000001

2004.

F0301.EPS

Figure 3.1 Position of Non-slip Seats

3-1

3. Measurement

3.2 Measurement Procedures

Immersing the sensor

Immerse the sensor so that the protective cover part goes under the sample solution level. The sensor does not need to be immersed deeply.

When using a KCl refillable type sensor, the filling solution level must be above the level of solution being measured. This is to prevent the KCl filling solution from being mixed with the sample solution.

Fill hole (left open during measurement)

Level of filling solution

Level of sample solution

(refill when level is low)

Sample solution

KCl refillable type sensor must be immersed so filling solution level is above the level of sample solution.

Protective cover

F0302.EPS

Figure 3.2 How to Immerse the KCl Refillable Type Sensor

Bubbles trapped in the glass electrode tip may interfere with accurate measurement. Before taking measurements, check the electrode tip for bubbles. If present, gently shake the sensor, as shown in Figure 3.3, to dislodge bubbles from the tip.

Enlarged View of A

* No bubbles

Bubbles

allowed in tip.

Filling solution

F0303.EPS

Filling solution

Glass electrode tip

Figure 3.3 How to Dislodge Bubbles from Glass Electrode Tip

3-2

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3.3 Measurement Display Panel

When immersing the sensor in a sample solution, a measured pH (or mV) value will be shown on the display. There are three types of measurement display panels: the standard,

3. Measurement

day month yearSolution temperature

MEAS

key to cycle through these display panels.

MEAS

calendar, and clock display panels. Use

Standard panel Calendar panel Clock panel

pH value (or mV)

MEAS MEAS

3.4 Saving a Measured Value

There are two ways to save a measured value: holding temporarily and storing as a record in nonvolatile memory. Measured values stored in nonvolatile memory are not deleted even by replacing the batteries.

(1) HOLD

temporarily and the displayed value no longer changes. Press return to the measurement mode.

key is pressed during measurement, the currently measured value is held

HOLD

hour:minute

MEAS

F030301.EPS

key to

IM 12B03D02-01E

HOLD

MEAS

F030401.EPS

3-3

3. Measurement

(2) Data storage

DATA

If the

F/ENT

key is pressed during measurement, mark starts flashing. Press the

key, then currently measured data can be stored in nonvolatile memory. Data

stored are measured conductivity, measured temperature, date and time. Up to 300 data including individually deleted data can be stored. If you attempt to store more data,

will be displayed.

If is displayed before the data number has reached 300, run defrag referring to Section 5.3 (15), “Defrag memory (DFLG) panel.” This will free up memory occupied

by deleted data, allowing data to be stored newly. To check stored data, refer to Section

5.3 (1), “Display stored data (dAt) panel.”

Pressing

DATA

MEAS

key while mark is flashing cancels data storage and

returns the meter to measurement mode.

Abort data storage.

While is flashing, press or keys to abort data storage.

MEAS

Execute data storage.

Press key to store data while is flashing.

F/ENT

DATA

F030402.EPS

3-4

IM 12B03D02-01E

4. Calibration

Calibration using standard solutions means to measure the pH value of a certified standard solution and to adjust the pH meter so it reads the same value as the certified value of the standard solution. The PH72 meter can be calibrated automatically or manually.

The PH72 meter must be calibrated before measurement if:

• it has been stored for a long period;

• the electrode has been cleaned; or

• otherwise necessary.

Precautions

(1) Use certified standard solutions. Using deteriorated standard solutions will result

in inaccurate calibration. Standard solutions are available as spare parts (see Section 1.8).

Pour a portion of the standard solution into a calibration bottle (supplied) and use for calibration. Do not reuse the portion. Discard it and use a fresh portion for another calibration.

4. Calibration

(2) Do not press

results may be changed.

key unless calibration is needed. Otherwise, saved calibration

CAL

Before Calibration

The following should be checked and set before calibration.

(1) Contamination of the sensor

Make sure that no dirt or deposits are present on the sensor.

(2) Temperatur e setting

When using a sensor without a built-in temperature element, i.e., a needle type or test tube size pH sensor, the temperature of a standard solution to be used should be set into the meter. (Refer to Section 5.3 (2), “Manual temperature setting (M.tP) panel.”)

(3) Battery condition

Check the battery condition indicator for remaining life. If the indicator is flashing, calibration cannot be performed. Replace the batteries. (Refer to Section 2.1, “Installing the Batteries.”)

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4-1

4. Calibration

Error Messages during Calibration

If the meter detects an abnormality during calibration, , , or

may be displayed. In such a case take corrective actions referring to Chapter 7,

“Troubleshooting.”

Canceling Calibration

To cancel the calibration procedure, press measurement mode.

CAL

MEAS

key. The meter will return to

1-point and 2-point Calibrations

There are two types of calibrations: 1-point calibration using only one standard solution and 2-point calibration using two standard solutions. One-point calibration is a simplified calibration method which can be used only when the anticipated pH values of sample solutions are near the certified pH value of a standard solution used for calibration. Twopoint calibration is generally recommended.

Calibration results are not affected by turning off the power and saved until the next calibration or the initialization of calibration parameters (see Section 5.3 (11)). The last two calibration results are saved in the meter. Therefore, for 1-point calibration, first initialize calibration parameters and then perform a 1-point calibration, or without initializing, perform a 1-point calibration twice using the same standard solution.

4-2

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4.1 Automatic Calibration

In automatic calibration the Model PH72 Personal pH/ORP Meter automatically recognizes standard solutions being used and calibrates itself using values of Table 4.1. Two types of standard solutions are preprogrammed: NIST (solutions prepared in accordance with Japanese standards, factory default) and US (solutions prepared in accordance with the U.S. standards). If NIST is selected, the meter recognizes standard solutions with pH 2, 4, 7, 9, and 12. The meter recognizes standard solutions with pH 4, 7, and 10 if US is selected.

Table 4.1 pH-Temperature Relationship in pH Standard Solutions

d NIST

Temperature 8C

Std. Solution

pH2 pH4 pH7 pH9

pH12

d US

Temperature 8C

Std. Solution

pH4 pH7

pH10

Before Automatic Calibration

0 5 10 15 20 25 30 35 40 4550

4.003

6.984

9.464

13.423

1.668

3.999

6.951

9.395

13.207

1.670

3.998

6.923

9.332

13.003

1.672

3.999

6.900

9.276

12.810

1.675

4.002

6.881

9.225

12.627

1.679

4.008

6.865

9.180

12.454

1.683

4.015

6.856

9.139

12.289

1.688

4.024

6.844

9.102

12.133

1.694

4.035

6.838

9.068

11.984

1.700

4.047

6.834

9.038

11.841

1.707

4.060

6.833

9.011

11.705

1.715

4.075

6.834

8.985

11.574

0 5 10 15 20 25 30 35 40 4550

4.000

7.120

10.317

3.998

7.090

10.245

3.997

7.060

10.179

3.998

7.040

10.118

4.001

7.020

10.062

4.005

7.000

10.012

4.010

6.990

9.966

4.018

6.980

9.926

4.027

6.980

9.889

4.038

6.978

9.856

4.050

6.970

9.828

4.064

6.980

9.828

Make sure that the correct type of standard solutions to be used for automatic calibration has been selected. (Refer to Section 5.3 (10), “Standard solution setting (Std) panel.”)

4. Calibration

55 60 70 80

1.723

1.743

4.126

6.845

8.921

1.766

4.164

6.859

8.885

T0402.EPS

4.091

6.836

8.962

11.449

55 60

4.080

6.980

9.828

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4-3

4. Calibration

d Procedure

Example 1: 2-point calibration using pH 7 and pH 4 standard solutions

Water

POWER

Calibration at 2nd point

Wash sensor with water thoroughly.

Wash sensor with water thoroughly (or wash in water in beaker).

to select auto calibration (AUto)

Auto calibration in progress

F/ENT

Water

Wipe off washing water

from sensor thoroughly and then immerse sensor in standard solution.

( to select auto calibration (AUto))

Auto calibration in progress

Wipe off washing water from sensor thoroughly

and then immerse sensor in standard solution.

(1st point)

Std. sol.

(2nd point)

Std. sol.

Auto calibration at 1st point

After a few seconds

Wait until reading stabilizes.

CAL

Auto calibration at 2nd point

After a few seconds

Wait until reading stabilizes.

CAL

is complete

F/ENT

The last two calibration results are saved in the meter. Therefore, for 1-point calibration, perform a 1-point calibration twice using the same standard solution, or initialize calibration parameters (refer to Section 5.3 (11), “Initialize calibration parameters (I.CP) panel”) before performing a 1-point calibration.

4-4

F0401.EPS

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4. Calibration

Example 2: Calibration of a sensor without a built-in temperature element* using a pH

7 standard solution

* Needle type or test tube size pH sensor

Water

POWER

Wash sensor with water thoroughly (or wash in

water in beaker).

25.08C fixed

Auto calibration in progress

to select auto calibration (AUto)

F/ENT

After a few seconds

Thermometer

Wipe off washing water from sensor thoroughly and then immerse sensor in standard solution.

F/ENT

Auto calibration is complete

Temperature set on 'M.tP' panel

Std. sol.

to enter standard solution temperature

Wait until reading stabilizes.

CAL

Input of standard solution

temperature

Standard solution temperature

F0402.EPS

For 2-point calibration, continue the procedure in the same way as Example 1. The difference between Example 1 and 2 is that appears on the display and the temperature of a standard solution should be entered manually.

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4-5

4. Calibration

4.2 Manual Calibration

When using standard solutions other than those preprogrammed for automatic calibration (see Section 4.1), calibration should be performed manually.

In 2-point calibration, manual calibration can be performed at both two points or manual calibration performed at one point (either 1st or 2nd) in combination with automatic calibration using a specified standard solution at the other point.

Note: Although manual calibration can be performed using standard solutions the same

as the ones preprogrammed for automatic calibration, it only makes the procedure more complicated. When using these standard solutions, automatic calibration should be generally performed.

d Precautions

(1) The difference between the pH values of two standard solutions to be used for 2-

point calibration must be at least 0.7 pH. If not, the meter will recognize the two standard solutions as the same calibration point. That is, the second calibration result will override the first calibration value, resulting in 1-point calibration.

(2) When using alkaline standard solutions, use the standard solution with lower pH

for the first point calibration. If not, may appear.

4-6

IM 12B03D02-01E

d Procedure

Example 3: Manual calibration

Water

POWER

Wash sensor with water thoroughly (or wash in

water in beaker).

Std. sol.

Wipe off washing water from sensor thoroughly

and then immerse sensor in standard solution.

4. Calibration

(2-point calibration)

Wait until reading stabilizes.

CAL

Prompting

to select manual calibration (MAn)

to enter

F/ENT

Manual calibration is complete

F/ENT

to confirm

F0403.EPS

For 2-pont calibration, continue the procedure following the dotted line. When using a sensor without a built-in temperature element (needle type or test tube size pH sensor), enter the temperature of standard solution following the procedure described in Section

4.1, Example 2.

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4-7

4. Calibration

4-8

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5. Keypad and Display Functions

There are eight membrane keys on the keypad of the Model PH72 Personal pH/ORP Meter. The following key functions are provided.

• Displaying a pH (or mV) value and temperature

• Displaying a pH (or mV) value, date and time

• Holding a pH (or mV) value and temperature

• Storing data — pH (or mV) value and associated information

• Function mode

• Calibration

Turns power on or off. Automatic Power Off function (default: 20 min).

Moves to calibration mode.

Holds the currently measured value.

Stores the currently measured value in memory.

Auto Power Off

POWER

CAL

HOLD

DATA

MEAS

F/ENT

Moves to measurement mode or switches measurement display panels. Also exits from the current function and returns to measurement mode.

Moves to function mode or confirms data entry.

Changes setting or

value.

F050001.EPS

IM 12B03D02-01E

5-1

5. Keypad and Display Functions

5.1 Keypad Functions

POWER

: Power On/Off key

Pressing and holding this key for at least one second when nothing is displayed on the LCD, will turn the meter on. The meter will be turned off by pressing and holding this key for at least two seconds when the meter is on. If no keys are pressed for a preset time, the meter turns off power automatically. (Refer to Section 5.3 (8), “Set Auto Power Off time (A.oFF) panel.”)

: Calibration key

CAL

When pressed during measurement, mark turns on and the meter moves to calibration mode. To return to measurement mode, press

: HOLD key

HOLD

CAL

When pressed during measurement, mark turns on and the currently displayed measured pH (or mV) value and temperature are held. Pressing will turn mark off and return the meter to measurement mode.

: DATA key

DATA

HOLD

MEAS

key.

MEAS

key

When pressed during measurement, mark flash and the currently displayed measured pH (or mV) value and temperature are held temporarily. Pressing while mark is flashing, will store the held data in memory. After the data is stored successfully, the meter returns to measurement mode automatically. To cancel data storage, press

DATA

MEAS

key while mark is flashing. mark

will turn off and the meter will return to measurement mode.

MEAS

: Measurement key

In measurement mode each press of this key cycles through three measurement display panels. (Refer to Section 3.3, “Measurement Display Panel.”) Pressing this key in other modes will return the meter to measurement mode. If you want to cancel any operation, press this key to return to measurement mode.

: Setting change keys

Used to change settings.

5-2

F/ENT

key

IM 12B03D02-01E

5. Keypad and Display Functions

F/ENT

: Entry key

Pressing this key during measurement moves the display to function mode. (Refer to Section 5.3, “Function Modes.”) This key is also used to confirm data entry.

Beep sound

When a key is pressed, the meter acknowledges it using a beep sound.

(1) One beep

The meter will beep once confirming a valid key entry.

(2) Three beeps

The meter will beep three times if the key entry is invalid.

To disable the beep, refer to Section 5.3 (9), “Set beep on/off (bZ.o) panel.” Note that the volume of the beep sound is not adjustable.

IM 12B03D02-01E

5-3

5. Keypad and Display Functions

5.2 Display Items

Display items and their descriptions are provided below.

Battery condition indicator

Temperature setting mode Manual mode

Data mode

HOLD mode Calibration mode

Sensor check mode

(1) Battery condition indicator

Indicates the level of the remaining battery life stepwise. means that there is plenty of life left. A flashing means that the batteries are low and need to be replaced immediately. When the indicator is flashing, access to calibration mode by

pressing

key is rejected. To replace the batteries, first press

CAL

off power and make sure the display has been turned off, and then replace referring to Section 2.1, “Installing the Batteries.”

(2) T emperatur e setting mode

Appears while manual temperature setting is being performed. (Refer to Section 5.3 (2), “Manual temperature setting (M.tp) panel.”)

(3) Manual mode

Appears when a sensor without a built-in temperature element (needle type or test tube size pH sensor) is connected to the meter. (Refer to Section 2.6, “Manual temperature setting.”)

(4) Data mode

Appears when measured data are stored or when stored data are accessed. (Refer to Section 5.1, “Keypad Functions,” and Section 5.3 (1), “Display stored data (dAt) panel.”)

(5) HOLD mode

Appears while measured data are being held temporarily. (Refer to Section 5.1, “Keypad Functions.”)

(6) Calibration mode

Appears during calibration using standard solutions. (Refer to Chapter 4, “Calibration.”)

POWER

F050201.EPS

key to turn

(7) Sensor check mode

This mark may appear when:

• the pH electrode deteriorated significantly (check is performed during calibration);

• the standard solution used for calibration changed in quality;

• deposits are present on the electrode (check is performed during calibration).

If deposits are present, clean the sensor (see Section 6.2); or,

• calibration is performed improperly.

5-4

IM 12B03D02-01E

5.3 Function Mode

Outline

5. Keypad and Display Functions

Various functions are supported by function mode. Press

key while the meter is

F/ENT

in measurement mode to move to function mode. Note: The last selected and executed item is displayed when you move to function

mode. Use keys to cycle through the items listed in Table 5.1 in that order.

Setting Procedures

Use keys to move to the desired item. While the desired item is flashing, press

F/ENT

key to access that item panel. To return from function mode to measurement

mode, press

Item*

dAt M.tP PV.U

dEL.A dAtE

tIME ALM A.oFF bZ.o Std I.CP tP.U VEr dFLG

MEAS

key anytime.

Table 5.1 Function Mode Item List

Description

Display stored data Manual temperature setting Set measurement unit Delete all stored data Date setting

Time setting Alarm time setting

Set Auto Power Off time Set beep on/off Standard solution setting Initialize calibration parameters Set temperature unit

Check version number Defrag memory

*1: For displayed digital characters, see Alphanumeric Display Table in Preface. *2: "2" denotes that the item is not user configurable.

Default*

no dAtA 25 8C

2004, 1 (month), 1 (day) 0 hour 0 minute

oFF 20 min on nISt no

For details, refer to:

Item (1) Item (2) Item (3) Item (4) Item (5) Item (6) Item (7) Item (8) Item (9) Item (10) Item (11) Item (12) Item (13) Item (14)

T0501.EPS

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5-5

5. Keypad and Display Functions

Operating procedures on each panel are described below.

(1) Display stored data (dAt) panel

Shows stored data on the LCD with mark. When you access this panel, the last stored pH (mV) value and temperature will be displayed with the data number flashing at the lower left of the display. Pressing keys scrolls through all stored data. If no data are stored, “no dAtA” is displayed at the bottom of the display. Each press of

key cycles through the day/month, year, and time of the stored data, and “Delete

DATA

stored data” panels.

• Individual Deletion

By pressing displayed stored data can be deleted. First is flashing. Use keys to switch to flashing and then press of “dEL” will be deleted.

• Data Numbering after Deletion

The number displayed at the bottom left indicates the stored data number relative to the beginning of the data store. This number does not necessarily represent the number of stored data. If a data item is deleted, item numbers of data that follow it will be decreased by one.

• Data Display after Deletion

If a data item is deleted, the data item after it is displayed. If there is no data after the deleted data item (i.e., it was the last stored data item), the data item before the deleted data item is displayed.

F/ENT

key when “dEL” appears underneath the value, the currently

key. The stored data with the number to the left

F/ENT

When data item 012 (latest data) is deleted:

5-6

Item 012 is deleted, so item 011 becomes the latest.

When data item 011 is deleted

Item 011 is deleted, so item numbers of following items (only item 012 in this case) are decremented by 1.

F050300.EPS

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5. Keypad and Display Functions

Stored measurement data

Latest data

F/ENT

When no stored data.

F/ENT

DATA

F/ENT

to display other data

Day and month data item was stored

DATA DATA

"Delete stored data" panel

DATA

Delete stored data

F/ENT

Year data item was stored

DATA

Time data item was stored

IM 12B03D02-01E

F/ENT

F050301.EPS

5-7

5. Keypad and Display Functions

(2) Manual temperature setting (M.tP) panel

Used to input the temperature of a solution into the meter when using a sensor without a built-in temperature element (needle type or test tube size pH sensor). This setting is not required when a sensor connected has a built-in temperature element. The setting range is from -10.0 to 110.08C.

to set to confirm

F/ENT

F050302.EPS

(3) Set measurement unit (PV.U) panel

Used to set a pH unit for pH measurement or a mV unit for ORP measurement.

F/ENT

to proceed

F/ENT

to confirm

(4) Delete all stored data (dEL.A) panel

Used to delete all stored data. Press will be flashing. Use keys to select . Press data completely.

F/ENT

to proceed

F/ENT

to execute

key on the flashing “dEL.A” panel.

F/ENT

to toggle

to cancel

F050303.EPS

F/ENT

key to delete all stored

F050304.EPS

5-8

IM 12B03D02-01E

5. Keypad and Display Functions

(5) Date setting (dAtE) panel

Used to set the year (four digits), month and day in this order. Use keys to set the year, month, and day, and press

F/ENT

key to confirm each entry.

Year setting Month setting

F/ENT

Day setting

F/ENT

F050305.EPS

The calendar function will be valid through to year 2090.

(6) Time setting (tIME) panel

Used to set the time — hour (24-hour format) and minute in this order. Use keys to set the time and press

F/ENT

key to confirm each entry.

Hour setting (24-hr clock) Minute setting

F/ENT F/ENT

F/ENT

F050306.EPS

IM 12B03D02-01E

5-9

5. Keypad and Display Functions

(7) Alarm time setting (ALM) panel

Used to enable/disable the alarm clock and set the alarm clock in minutes and seconds. Use keys to select the desired alarm cycle: 7 days (everyday), 5 days (weekdays) or once. See Item (6), “Time setting (tIME) panel” for setting the time for alarm. The alarm sounds for about 15 seconds. Acknowledge the alarm by pressing any key. The alarm sound will stop. If no key is pressed (no acknowledgement), the alarm sounds for 15 seconds again 3 and 6 minutes after the preset alarm time. Note that the day of the week is not displayed.

F/ENT

alarm sounds at preset time every day

alarm sounds at preset time

from Monday to Friday

F/ENT

Hour setting (24-hr clock)

F/ENT

Minute setting

5-10

alarm sounds once at preset time

F050307.EPS

IM 12B03D02-01E

5. Keypad and Display Functions

(8) Set Auto Power Off time (A.oFF) panel

Used to set the automatic power off time. The meter turns off power automatically if no key is pressed during this preset time. The time range is from 1 to 120 minutes. If 0 is set, the Auto Power Off function will be disabled. Use the meter taking care to conserve the batteries.

to set

F/ENT

to confirm

F050308.EPS

(9) Set beep on/off (bZ.o) panel

The beep sound on key press can be enabled/disabled in this panel. Use keys to

F/ENT

key to confirm. Note that this beep setting does not

select on or off and press affect the alarm sounding (See Item (7)).

F/ENT

to turn ON (enable).

F/ENT

to turn OFF (disable).

(10) Standard solution setting (Std) panel

Used to select the type of standard solutions: NIST or US. The factory default is NIST. When using standard solutions prepared in accordance with the Japanese standards, use the meter with the factory default of NIST. Select US only when using standard solutions prepared in accordance with the U.S. standards. (Refer to Chapter 4, “Calibration.”)

F/ENT

IM 12B03D02-01E

to toggle

to confirm

F050309.EPS

F050310.EPS

5-11

5. Keypad and Display Functions

(11) Initialize calibration parameters (I.CP) panel

Used to initialize the parameters saved by calibration to default settings: slope at 1.000 and asymmetry potential at 0.0 mV.

F/ENT

to proceed

F/ENT

to execute

F/ENT

to toggle

to cancel

F050311.EPS

(12) Set temperature unit (tP.U) panel

Used to select the temperature unit: Celsius (8C) or Fahrenheit (8F). Use keys to

to confirm

F/ENT

key to confirm.

to toggle

F050312.EPS

select the desired temperature unit and press

F/ENT

(13) Check version number (VEr) panel

Used to check the version number of the program. This is not user configurable.

5-12

F/ENT

F050313.EPS

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5. Keypad and Display Functions

(14) Defrag memory (dFLG) panel

Up to 300 data can be stored. Unnecessary data can be individually deleted (refer to Item (1), “Display stored data”), but this individual deletion does not free up memory

occupied by deleted data. Therefore, may be displayed even though less than 300 data are stored. In such a case, use the defrag function to consolidate data and free

up the space occupied by deleted data, thereby allowing up to 300 data to be stored. While memory defrag is in progress, do NOT turn off the power. In addition, before

starting memory defrag check that there is enough battery life left to avoid battery shutoff during memory defrag.

• Procedure

F/ENT

Press

key on the flashing “dFLG” display. will be flashing. Use

keys to select , then press

F/ENT

key. While defrag is in progress, “WAIt” may

flash. (It may not flash depending on the amount of deleted data.) When defrag is complete, “End” appears.

F/ENT

to proceed

(may not appear if deleted data amount is small)

After a few seconds

F/ENT

to toggle

to cancel

to execute

F050314.EPS

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5-13

5. Keypad and Display Functions

5-14

IM 12B03D02-01E

6. Maintenance

6.1 For Optimum Meter Performance

The Model PH72 Personal pH/ORP Meter is simple to operate, but is a precision instrument. To ensure accurate results from the meter, the following precautions should be observed.

Flow Diagram

Measurement

MaintenanceCa l i b ration

Storage

F060101.EPS

Table 6.1 Precautions in Each Step

Calibration using standard solutions:

Calibration

Measurement

Maintenance

Storage

• 1- or 2-point calibration. 2-point calibration is recommended for accurate pH measurement.

• Always use certified standard solutions (pH 2, 4, 7, 9, 10, or 12).

Sample solution requirements:

• pH range: 0 to 14 pH

• Temperature: 0 to 808C (0 to 1008C when using needle type or test tube size pH sensor)

• After measurement, rinse off remaining sample solution from the electrode thoroughly.

• Avoid a place with high temperature and humidity.

• Keep the wetting cap (moisten the cotton wad in the cap with a few drops of water) attached to prevent the glass electrode and liquid junction from drying out.

6. Maintenance

T0601.EPS

IM 12B03D02-01E

6-1

6. Maintenance

6.2 pH Electrode Cleaning

Dirt or deposits on the glass electrode or liquid junction can often interfere with accurate measurement. Periodical cleaning is required depending on the nature of the solution being measured.

CAUTION

Do not apply physical shock or excessive force to the glass sensor, or it may break. Do not rub the glass membrane strongly, or it may be damaged or break.

• Suspended Solids, Adhesive Material, Microorganisms, Greasy Substances, etc.

Dirt or deposits on the glass electrode, liquid junction or temperature element should be removed. Clean using a cotton swab soaked with a neutral detergent, and rinse off with water. If necessary, use a toothbrush to clean.

Temperature element

Glass electrode

Liquid junction

Figure 6.1 How to Clean Using a Toothbrush

F0601.EPS

• Chemical Contaminants

Chemical contaminants can affect the electrode performance even though the electrode appears to be clean. If appears on the display, soak the electrode in dilute

hydrochloric acid (approximately 0.1 mo/l, 1 to 2 pH) for 10 to 20 minutes (this process is called acid cleaning). Since an electrode deteriorates gradually in service, its performance cannot be recovered completely even if acid cleaning is conducted. After cleaning, rinse off cleaning solution from the electrode with water.

Note: Dilute hydrochloric acid is commercially available at a pharmacy. Handle with

care.

6-2

IM 12B03D02-01E

0.1 mol/l dilute hydrochloric acid

6. Maintenance

After 10 to 20

minutes

Cleaning water

Soak in 0.1 mol/l hydrochloric acid

Rinse thoroughly in water

Figure 6.2 Acid Cleaning

6.3 Sensor Replacement

Since a pH sensor undergoes chemical changes with time, its performance deteriorates gradually. Under normal operating conditions a sensor can be used for one or two years. Sensor deterioration, however, speeds up depending on the nature of a sample solution, e.g., a high temperature solution. Storage conditions also affect the sensor life.

If or appears while calibration is being performed with a sensor for which is displayed, replace the sensor.

6.4 Rehydrating the Glass Electrode

A dry glass electrode gives fluctuating pH readings. If a glass electrode has dried up, soak it in water (tap water) for 1 to 2 hours or longer to rehydrate. The sensor will give stable pH readings.

F0602.EPS

IM 12B03D02-01E

6-3

6. Maintenance

6.5 Replenishing the Electrode with Filling Solution (KCl solution)

Replenishment is required only when a KCl refillable type combination sensor is used. An electrode filling solution leaks from the liquid junction little by little during measurement. When the level of filling solution drops to the level shown in Figure 6.3, replenish with a 3.3 mol/l KCl solution supplied.

CAUTION

A syringe tip is sharp. Handle with care.

Syringe (supplied)

Filling solution level

Fill hole for KCl solution

20mm

Protective cover

Replenish when filling solution level drops to the level shown above.

Figure 6.3 Replenishment of Filling Solution

How to fill using syringe

F0603.EPS

6-4

IM 12B03D02-01E

6.6 Cleaning and Drying Connectors

Deteriorated insulation between connector pins can cause inaccurate readings. To remove stains and/or moisture that may cause deteriorated insulation, clean the connector with a dry cloth or a cloth moistened with anhydrous alcohol. If necessary, use a dryer.

O-ring

Wipe off stains and/or moisture on meter connector with a dry cloth.

Check that there are no stains on the O-ring.

Hot air

Use a dryer if necessary to remove moisture from connector of sensor cable.

6. Maintenance

F060601.eps

CAUTION

Use anhydrous alcohol to clean the connectors so no moisture remains. Dry connectors completely.

IM 12B03D02-01E

6-5

6. Maintenance

6.7 Storage and O-ring/Gasket Replacement

• Storage Precautions

Care is required when storing the meter and sensor. To maintain in good condition, observe the following:

(1) Before storage, wash off remaining sample solution from the sensor with water.

Deposits on the liquid junction, if any, must be removed thoroughly, or the junction may be clogged. A clogged junction will cause invalid measurements, e.g., unstable pH readings.

Keep a wetting cap attached to the sensor. For KCl refillable type sensors, seal the fill hole with a plug.

(2) Leave the sensor connected to the meter body to protect the connectors and O-ring

from staining. Contamination may cause deteriorated insulation of connectors or poor water resistance by the O-ring.

(3) Do not place any object on top of the sensor or on the top of the PH72 meter.

Attach wetting cap containing cotton wad moistened with a few drops of water.

For KCl refillable type sensor, seal fill hole with plug.

Protective cover

Wetting cap

Figure 6.4 Sensor Storage Condition

• Storage Location

When not in use, store the meter and sensor in a safe place. If it is to be stored for a long period, store it in a place:

• With low humidity at or near normal temperatures

• Not exposed to direct sunlight or water

• No corrosive gases are present

• Replacing the O-ring and Gasket

A gasket in the battery box and an O-ring on the sensor connector of the meter can be replaced. Heavily contaminated or damaged gasket and/or O-ring should be replaced.

CAUTION

When installing an O-ring and gasket, clean them and their mounting surfaces with a cloth moistened with alcohol so that they are free from dirt. Otherwise, water resistance may not be assured.

6-6

F0604.EPS

IM 12B03D02-01E

6. Maintenance

(1) Replacing the O-ring

Install the O-ring on the cylindrical flat part of the connector, as shown below.

O-ring

F060701.EPS

(2) Replacing the Gasket

Install the gasket on the groove on the battery box so the raised part fits in place as shown below. The gasket is symmetrical right to left and front to back.

Gasket

PH72 meter top

Raised part

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F060702.EPS

6-7

6. Maintenance

6-8

IM 12B03D02-01E

7. Troubleshooting

7.1 Causes of Abnormal Readings and Errors

If the pH reading is unstable or abnormal, or an error message appears, during measurement or calibration, check the following:

(1) Improper maintenance or usage (2) Expired consumables (3) Failure

If any trouble occurs, determine the cause and take corrective actions referring to Section

7.2. If the trouble cannot be fixed, contact your nearest Yokogawa sales office.

d Unstable reading

Symptom

d Abnormal reading d Error message

Expired consumables

d Electrode d Batteries

Improper maintenance

d Improper calibration d Stained electrode d Dry glass electrode d Deteriorated insulation of connectors

7. Tr oubleshooting

IM 12B03D02-01E

Meter failure

Contact Yokogawa

F0701.EPS

Figure 7.1 Causes of Abnormal Symptoms

7-1

7. Tr oubleshooting

7.2 Error Messages, Possible Causes, and Corrective Actions

Table 7.1 Error Message

Error Message*

Err1 Err2 Err3 Err4 Err5 Err6

*1: For displayed digital characters, see Alphanumeric Display Table in Preface.

Description

Unstable input emf Abnormal asymmetry potential Abnormal slope or calibration temperature Out of measuring range Out of temperature measuring range Meter electronics failure

Occurrence

During calibration

During measurement

(1) Err1 Unstable input emf

Appears during calibration. A calibration result is accepted when the variation of input emf for 10 seconds falls

within 61 mV (approximately 60.02 pH equivalent). If the variation for 10 seconds cannot stabilize and is outside the range of 61 mV even after 3 minutes has elapsed in calibration, an Err1 message will appear.

Possible Causes:

• Dry electrode.

• Clogged liquid junction.

• Insulation failure in electronics.

• Sensor immersed improperly.

Corrective Actions:

• Leave the sensor in a standard solution until the reading stabilizes, and then try recalibration.

• Remove dirt or deposits from the liquid junction. (See Section 6.2.)

• Remove stain or moisture from the connectors. (See Section 6.6.)

• Immerse the sensor properly (See Section 3.2.)

• Immerse the sensor in water for 1 to 2 hours or longer to rehydrate. (See Section

6.4.)

T0701.EPS

7-2

IM 12B03D02-01E

7. Tr oubleshooting

(2) Err2 Abnormal asymmetry potential

Appears during calibration. A sensor deteriorates in service and the emf deviates from the initial one. If the

difference increases and exceeds the limit that can be compensated by calibration, an Err2 message will appear. It will also appear if the pH value of the standard solution is abnormal or if the asymmetry potential is outside the range of -96 to 120 mV.

Possible Causes:

• Clogged liquid junction.

• Insulation failure in electronics.

• Improper standard solution.

• Dirt or deposits on electrode.

• Electrode filling solution has been depleted.

• Expired battery life.

• Electrode contaminated with standard solution.

Corrective Actions:

• Remove dirt or deposits from the liquid junction. (See Section 6.2.)

• Remove stain or moisture from the connectors. (See Section 6.6.)

• Use properly prepared standard solutions. (See Chapter 4)

• Perform acid cleaning. (See Section 6.2.)

• For KCl refillable type sensors, replenish with filling solution. (See Section 6.5.)

• Replace the sensor. (See Section 1.6.)

• For KCl refillable type sensors, replace the filling solution.

IM 12B03D02-01E

7-3

7. Tr oubleshooting

(3) Err3 Abnormal slope or calibration temperature

Appears during calibration. In the Model PH72 Personal pH/ORP Meter standard solution data (NIST and US) are

preprogrammed. During automatic calibration the meter recognizes standard solutions being used based on these data. If standard solutions other than the preprogrammed ones are used, an Err3 message will appear. It will also appear if the slope is outside the range of 65 to 125%.

Possible Causes:

• Defective standard solutions.

• Dirty electrode.

• Clogged liquid junction.

• Insulation failure in electronics.

• Outside calibration temperature range.

• Improper manual temperature setting.

Corrective Actions:

• Use properly prepared standard solutions. (See Chapter 4.)

• Remove dirt or deposits from the electrode and liquid junction. (See Section 6.2.)

• Remove stain or moisture from the connectors. (See Section 6.6.)

• Perform calibration within the calibration temperature range.

• Set the temperature of the solution used manually and correctly. (See Section 5.3 (2).)

(4) Err4 Out of measuring range

Appears during measurement. The Model PH72 Personal pH/ORP Meter can measure the pH value of a solution in the

range of 0 to 14 pH. If the pH value of the solution being measured is significantly outside this range (-2 pH or lower and 16 pH or higher), an Err4 message will appear. It will also appear if the electrode is dirty or has dried out. When a new sensor is used for the first time, an Err4 message may appear. This is due to low hydrophilic property a new sensor may have.

Possible Causes:

• Solution pH is significantly outside the measuring range of 0 to 14 pH.

• Dry electrode.

• Dirt or deposits on electrode.

Corrective Actions:

• Immerse the sensor in water for 1 to 2 hours or longer to rehydrate. (See Section

6.4.)

• Remove dirt or deposits from the sensor. (See Section 6.2.)

7-4

IM 12B03D02-01E

(5) Err5 Out of temperature measuring range

Appears during measurement. With the Model PH72 Personal pH/ORP Meter, a general-purpose sensor can be used in

the temperature range of 0 to 808C and a needle type or test tube size sensor in the temperature range of 0 to 1008C. If the operating temperature is significantly outside this measuring range (below -10.08C or above 1208C), an Err5 message will appear.

Possible Cause:

• Operating temperature is significantly outside the measuring range.

Corrective Action:

• Adjust the temperature of the solution so it falls within the measuring range (0 to 808C for general purpose types and 0 to 1008C for needle type or test tube size sensor).

(6) Err6 Meter electronics failure

Possible Cause:

• Failure of electronics.

Corrective Action:

• Contact your nearest Yokogawa sales office.

7.3 Causes of Abnormal Measured Values

If error messages do not occur, but measured values seem incorrect, check the following:

• Are proper standard solutions used?

• Is the sensor connected to the meter securely?

• Are air bubbles trapped in the electrode tip?

• Has the electrode dried out?

• Is the electrode dirty?

• Is the sensor damaged or dirty?

• Is the electrode immersed in the sample solution properly?

• Has the level of the electrode filling solution dropped (for KCl refillable type sensors)?

• Is the electrode filling solution contaminated with the sample solution (for KCl refillable type sensors)?

• Has the actual temperature of the solution been set properly (for a needle type or test tube size pH sensor)?

7. Tr oubleshooting

IM 12B03D02-01E

7-5

7. Tr oubleshooting

7.4 Other Conditions

• An alarm sounds

The alarm is set to sound at the preset alarm time. Refer to Section 5.3 (7), “Alarm time setting (ALM) panel.”

• Beeps

The beep sound to acknowledge a key press can be enabled/disabled. Refer to Section

5.3 (9), “Set beep on/off (bZ.o) panel.”

• appears

This indicates that the electrode has deteriorated. The electrode may be used continuously even after this mark appears. If a or message appears in addition to this mark, however, replace the sensor with a new one immediately. This mark will also appear when deteriorated or poor quality standard solutions are used

for calibration, when dirt or deposits are present on the electrode, or when calibration is performed improperly. When it appears, perform acid cleaning (see Section 6.2) and recalibrate using fresh standard solutions.

• appears

This does not indicate any failure if a sensor without a built-in temperature element (a needle type or test tube size pH sensor) is used. If this mark appears, manually set the temperature of a solution. (See Section 5.3 (2).)

If it appears even though a sensor with a built-in temperature element is used, the temperature measuring circuit may have broken. In this case the meter performs temperature compensation assuming that the solution temperature is 258C. Therefore, the bigger the difference between the actual temperature of the solution and 258C, the bigger the error between the displayed measured value and the true value. For reliable measurement replace the sensor with a good one.

This mark will also appear if the sensor is not connected properly. Make sure that the connectors are securely connected.

7-6

IM 12B03D02-01E

8. ORP Meter

8.1 ORP Measurement

Use a dedicated ORP sensor for ORP (oxidation-reduction potential) measurement. The ORP sensor is a KCl refillable type with a platinum sensing electrode and looks the same as a KCl refillable type pH sensor. The measuring temperature range of the ORP sensor is 0 to 808C, the same as that of the pH sensor.

• The default setting for measurement unit of the Model PH72 Personal pH/ORP Meter is pH. Press

(3), “Set measurement unit (PV.U) panel” to move to the display with mV unit.

Figure 8.1 Example of Displayed ORP Value

• Immerse the sensor in a sample solution and read after the reading has stabilized.

F/ENT

key and follow the procedure described in Section 5.3

F0801.EPS

8. ORP Meter

• To hold a measured value, press measured value. (See Section 3.4.)

Note: Unlike pH sensors, ORP sensors do not require calibration. A temperature element incorporated in an ORP sensor is used for measuring the

temperature of a solution, e.g., measuring the temperature of a check solution during sensor check (see Section 8.3).

IM 12B03D02-01E

HOLD

key. Press

DATA

key to save a

8-1

8. ORP Meter

8.2 Maintenance of ORP Sensors

Maintenance of ORP sensors is in accordance with that of pH sensors. (Refer to Chapter 6, “Maintenance.”)

Cleaning the Platinum Electrode and Liquid Junction

Dirt or deposits on the platinum electrode or liquid junction may interfere with accurate measurement. Periodical cleaning is required depending on the nature of the solution being measured.

As in the same manner for pH sensors, use a cotton swab or brush to clean. (See Section

6.2.) If the potential is outside the tolerance after the sensor check has been performed according to the procedure in Section 8.3, clean the platinum of the sensing electrode. Polish the platinum using a cream cleanser, alumina powder, or baking soda (sodium bicarbonate), and then wash with water.

CAUTION

Do not apply physical shock or excessive force to the glass sensor, or it may break.

Replenishment of Electrode Filling Solution

When the level of KCl filling solution drops, replenish following the procedure in Section 6.5.

8-2

IM 12B03D02-01E

8.3 Checking the ORP Sensor

Use a check solution to verify that the ORP sensor operates properly. The oxidationreduction potential of the check solution to be used should have been correctly determined by a normal ORP sensor. The following explains how to check an ORP sensor using a quinhydrone reagent (spare part).

Preparing a Quinhydrone Solution

Prepare a 250 ml solution in a wide mouthed bottle by dissolving one pack of quinhydrone reagent in deionized water. If the temperature of deionized water is low, the reagent may not be dissolved completely and some powder may float on the surface of the solution. This will not affect the ability of the solution. A quinhydrone solution may change with time, so it should be prepared and used within the same day.

Procedure

(1) Pour 50 to 100 ml of the prepared check solution into a clean container (200 ml). (2) Rinse off the remaining sample solution, if any, from the electrode with water and

then wipe off water drops.

(3) Immerse the electrode tip in the check solution and wait until the reading has

stabilized. This should take 5 to 10 minutes.

(4) Read the mV value and solution temperature. The mV reading at the solution

temperature must be within the tolerance (640 mV) shown in Figure 8.2. If it falls within the tolerance, the sensor is normal. If not, clean the sensor following the procedure in Section 8.2.

8. ORP Meter

IM 12B03D02-01E

8-3

8. ORP Meter

400

Quinhydrone solution

300

200

100

Oxidation-reduction potential (mV)

Tolerance

0 10 20 304050

Temperature (8C)

F0802.EPS

Figure 8.2 Oxidation-Reduction Potential of Check Solution

8-4

IM 12B03D02-01E

9. T echnical Information

9. Technical Information

9.1 Measurement Principle of pH Meter (Glass Electrode Method)

A pH meter makes use of the potential difference developed between the two sides of a thin glass membrane that separates two solutions with different pH. Figure 9.1 shows the schematic diagram of the measurement principle. A glass electrode is filled with a pH 7 solution and has an inner electrode that measures the potential difference corresponding to the pH difference between the internal solution and the test solution. A reference electrode has a constant potential irrespective of the pH of the test solution, which is supported by potassium chloride (KCl) solution. It prevents the reference electrode from making contact with the test solution but itself has electrical contact with the test solution through the liquid junction. A voltmeter measures the potential difference between the electrodes. As the membrane resistivity is high (several 10 to 100 MΩ), the voltmeter with high input impedance is required. The external leak resistance should also be sufficiently high (1012 Ω or greater).

Voltmeter

pH electrode

Inner electrode

Reference electrode

Glass membrane

IM 12B03D02-01E

pH7

Test solution

Figure 9.1 Measurement Principle of pH Meter

KCl solution

Liquid junction

F0901.EPS

9-1

9. T echnical Information

9.2 Relationship between EMF of Glass Membrane and pH Value

The relationship between the potential difference (electromotive force) developed across the glass membrane and the pH value had been studied and the theoretical values were determined. Actual values, however, do not match the theoretical values due to manufacturing variations or deterioration with time. Therefore, a pH meter must be calibrated using standard solutions.

The emf of a glass electrode is affected by temperature. To compensate for this temperature effect is called “temperature compensation” which is essential for pH measurement.

Figure 9.2 shows the diagram of glass electrode membrane. Both membrane surfaces in contact with solutions are hydrated and the hydrogen ion activity in these hydrated layers is constant. A boundary potential develops depending on the ratio of the hydrogen ion activities of the hydrated layer and of the solution. This boundary potential, e, is expressed from the Nernst equation as follows.

e 5 2

e 5 2 pH 1C (sample solution side)

2.3026 R T

Where:

pH 1C (internal solution side)

iii

R : gas constant, 8.3145 [J/(mol·K)] T : absolute temperature (t [8C]1273.15) [K]

F : Faraday constant, 9.6485310 [C/mol] C : potential at interface between glass and internal solution

C : potential at interface between glass and sample solution

Given the potential at internal solution side is reference, the difference across the membrane eg is:

e 5 e 2e 5 (pH 2pH )1(C 2C )

g iiiSSS

2.3026 R T

To determine the difference of membrane potentials, two inner electrodes are incorporated in a glass electrode and a reference electrode and the difference in potential at two electrodes is measured by a pH converter with high input impedance. This potential difference Eg is expressed as follows when the difference of single electrode potential of the two inner electrodes and CS – Ci in equation 9.3 are collectively represented by EAS.

(9.1)

(9.2)

(9.3)

2.3026 R T

E 5 (pH 2pH )1E

g i S AS

E 5 (54.2010.1984 t) 3 (pH 2pH )1E

g i S AS

(9.4)

(9.5)

In the equation, pHi is the pH buffer solution filled in the glass electrode so the pH should be constant. Using a solution (pH standard solution) with known pH as pHS at a certain temperature, the relationship between millivolt and pH can be determined, thereby the pH can be directly derived from the membrane potential difference, as shown in Figure 9.3.

9-2

IM 12B03D02-01E

Sample solution side

Boundary layers

Internal solution side

9. T echnical Information

Hydrated layers on glass

F0902.EPS

Figure 9.2 Diagram of Glass Membrane

500 400 300 200 100

E (mV)

-100

-200

-300

-400

Alkaline error

-500

10 12 14

F0903.EPS

4 6

Figure 9.3 Relationship between Glass Electrode Potential and pH

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9-3

9. T echnical Information

9.3 Temperature Compensation

In equation 9.3, 2.3026RT/F represents the emf per pH unit and varies depending on temperature.

Table 9.1 EMF per pH (values of 2.3026RT/F)

(8C)

5 10 15 20 25 30

2.3026RT/F

(mV)

54.20

55.19

56.18

57.18

58.17

59.16

60.15

Temperature

(8C)

35 40 45

50 55

60 65

2.3026RT/F (mV)

61.14

62.14

63.13

64.12

65.11

66.11

67.10

Temperature

(8C)

70 75 80 85 90 95

100

2.3026RT/F

(mV)

68.09

69.08

70.07

71.07

72.06

73.05

74.04

T0901.EPS

Temperature

Table 9.1 presents the relationship between the temperature and the emf per pH unit, and the relationship between the pH and the emf at each temperature is shown in Figure 9.4. Measurement without temperature compensation will result in measured pH values including errors as shown in Table 9.2.

The PH72 meter automatically modifies the calibration line according to the temperature measured by the temperature element incorporated in an electrode (except needle type and test tube size pH sensors).

+500

pH7

4 6

pH2

10 12 pH14

9-4

-500

Figure 9.4 pH vs EMF at Each Temperature

08C 208C

608C 808C

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IM 12B03D02-01E

9. T echnical Information

Table 9.2 Deviations from True Values in Measurement without

Temperature Compensation

Temp.(8C)

1 3 5 7

9 11 13

0.50

0.34

0.17

0.00

-0.17

-0.34

-0.50

0.10

0.07

0.03

0.00

-0.03

-0.07

-0.10

0.00

-0.30

-0.20

-0.10

0.00

0.10

0.20

0.30

-0.70

-0.47

-0.23

0.00

0.23

0.47

0.70

-1.11

-0.74

-0.37

0.00

0.37

0.74

1.11

T0902.EPS

In addition, the pH value of a solution changes with temperature. The pH value of a solution at the actual temperature may be converted into the one at a reference temperature. This is generally called “conversion to reference temperature,” which is different from the temperature compensation.

9.4 The Asymmetry Potential

Theoretically when identical buffer solutions (pHi = pHS) are present on both sides of the membrane of a glass electrode, the emf should be 0 mV. In reality, some potentials (CS – Ci) develop depending on the thickness of the glass membrane, heat treatment process, service history, or other factors. This is called the real asymmetry potential. In addition to this potential, the difference in single electrode potential between the inner electrodes of the glass electrode and of the reference electrode and a liquid junction potential* are collectively referred to as the apparent asymmetry potential or just the asymmetry potential. This asymmetry potential is EAS in equation 9.4.

* Liquid junction potential occurs due to dirt or clogging of the liquid junction or

other factors.

IM 12B03D02-01E

9-5

9. T echnical Information

9.5 The Alkaline Error

As shown in Figure 9.5, the emf of a glass electrode deviates from the linear value on the alkaline side. This is called the alkaline error. The magnitude of the alkaline error varies depending on the glass membrane compositions. The alkaline error is likely to occur with the presence of sodium and lithium and even with the same pH, it varies depending on the types and concentrations of cations and on the temperature.

Acid error

Theoretical value

E (mV)

1 43 5

pHx

EMF at pH 7

98 116 10 12 pH

Slope difference

Alkaline error

F0905.EPS

Figure 9.5 EMF Characteristics of Glass Electrode

Solution temperature

at 258C

Alkaline error (mV)

Test solution pH

3mol/l-Na

3mol/l-K

3mol/l-NH

13 14

F0906.EPS

Figure 9.6 Ion Type vs Alkaline Error

9-6

IM 12B03D02-01E

9. T echnical Information

Alkaline error (mV)

Solution temperature at 258C

Test solution pH

3mol/l-Na

1mol/l-Na

0.1mol/l-Na

13 14

F0907.EPS

Figure 9.7 Ion Concentration vs Alkaline Error

9.6 The Acid Error

The acid error also varies depending on the glass membrane compositions and the types of acids. It increases gradually with immersion time and finally reaches equilibrium. Once a glass electrode has the acid error, it cannot recover soon even by being soaked in a neutral solution and needs considerable time. Practically, the acid error is small compared to the alkaline error so that it is negligible.

-1

H2SO

H3PO

Acid error (mV)

HCl

Figure 9.8 Acid Type vs Acid Error

Solution temperature at 258C

F0908.EPS

IM 12B03D02-01E

9-7

9. T echnical Information

9.7 Calibration Calculation

The PH72 meter is calibrated at 2 points using 2 standard solutions. The first calibration is done so a certain line is drawn through the calibration point (Figure 9.9). The second calibration is done so a line is drawn through the first and second calibration points (Figure 9.10). One-point calibration is a simplified method where only the first calibration of 2-point calibration is performed.

Note: A calibration point is the emf corresponding to the pH value of a standard

solution used. (Refer to Table 4.1.)

Calibration line

+mV

Theoretical line

pH7, 0mV

pH0

Calibration point

-mV

Figure 9.9 Calibration at First Point

Second calibration point

+mV

Theoretical line

pH7, 0mV

pH0

First calibration point

-mV

Calibration line (slope)

Figure 9.10 Calibration at Second Point

pH14

F0909.EPS

pH14

Asymmetry potential

F0910.EPS

9-8

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9. T echnical Information

9.8 ORP (Oxidation-Reduction Potential)

In general, oxidation is the gain of oxygen or the loss of hydrogen, and reduction is the loss of oxygen or the gain of hydrogen. In the electrochemistry field, oxidation is defined as the loss of electrons and reduction is defined as the gain of electrons. These reactions are reversible and expressed as follows:

Ox 1 n e Red

where Ox is the oxidized form of substance, Red is the reduced form of substance, e– is an electron, and n is the number of electrons transferred. If an inert electrode (not react with substances in a solution or not corroded by a solution, e.g., platinum or gold) is immersed in a solution where oxidized and reduced forms of substances are present, the electrode will acquire the potential that corresponds the ratio of activities of both forms of substances and reaches its equilibrium. This potential is called the oxidation-reduction potential (ORP). The ORP, E in millivolts, between the indicator electrode and the reference electrode is expressed from the Nernst equation as follows.

E 5 E 1 ln

Where:

R T

n F

[Ox]

[Red]

E : oxidation-reduction potential when potential of standard hydrogen electrode* is 0

E : standard electrode potential when [Ox]5[Red] R : gas constant F : Faraday constant n : number of electrons T : absolute temperature

[Ox] : activity of oxidized form of substance [Red] : activity of reduced form of substance

Standard Hydrogen Electrode (SHE)

(9.6)

IM 12B03D02-01E

Potentiometer

Indicator electrode (Pt)

Test solution

Figure 9.11 Measurement System of ORP Meter

Reference electrode

F0911.EPS

9-9

9. T echnical Information

9.9 Reference Electrode

The oxidation-reduction potential in measurement is a value relative to the reference electrode. If different types of reference electrodes are used, the oxidation-reduction potentials of identical solutions are apparently different. In the electrochemical field, the hydrogen electrode is generally used as a reference electrode. However, it has complicated construction and is impractical. Therefore, in Yokogawa's ORP sensors, an Ag/AgCl electrode filled with a 3.3 mol/l KCl solution is used as a reference electrode.

The relationship between the Ag/AgCl electrode and the standard hydrogen electrode can be derived from the Nernst equation based on the following cell scheme.

Electrode (Pt) H2Electrolyte solution Liquid junction or salt bridge KCl(m) AgCl Ag

The reaction formula is

AgCl 1 e Ag 1 Cl

equation 9.6

R T

a a

AgCl

Cl-Cl

AgCl

(Activity of solid a51, then a 51, a 51)

(a5mg m: molality, g: activity coefficient)

KCl 6KCl

R T

E 5 E 1 ln

AgCl

solution instead of the activity coefficient of Cl– (actual measurement is impossible).

AgCl

5 E 2 ln a

5 E 2 ln m g

R T

can be obtained using the average ion activity coefficient, g

AgCl

E 5 E 2 ln m g

The relationship of the molality m, molarity c, activity coefficient at molality g6, and activity coefficient at molarity y6, is as follows.

, If a represents the activity, from

AgClAg

6KCl

(9.7)

, of the KCl (m)

From equations 9.7 and 9.9,

9-10

m 5

y 5 g

E 5 E 2

AgCl

d20.001 c W

m d

R T

m : molality [mol/kg] c : molarity [mol/l] or [M] d : density of solution [g/cm W : molecular weight of solute d : density of solvent [g/cm

g : activity coefficient at molality

y : activity coefficient at molarity

c y

]

(9.8)

(9.9)

(9.10)

IM 12B03D02-01E

9. T echnical Information

Obtained from equation 9.10, the potential of the Ag/AgCl electrode filled with a 3.3 mol/l KCl solution, E' electrode as shown in Figure 9.12.

To convert E'

AgCl

E 5 E 1 E 1 E [mV]

SHE

E : oxidation-reduction potential when reference electrode is SHE

SHE

, has the temperature characteristic for the standard hydrogen

AgCl

to the value for the standard hydrogen electrode,

AgCl

(9.11)

E : oxidation-reduction potential when reference electrode is Ag/AgCl electrode filled with 3.3 mol/l KCl solution

E : potential of Ag/AgCl electrode filled with 3.3 mol/l KCl solution (vs SHE)

AgCl

E : liquid junction potential (average liquid junction potential between KCl

and test solution is approximately 3 mV)

250

AgCl

200

(vs SHE), E' [mV]

150

IM 12B03D02-01E

3.3mol/l KCl-Ag/AgCl Electrode Potential

Temperature [8C]

6040200

F0912.EPS

Figure 9.12 Temperature Characteristic of Potential of Ag/AgCl

Electrode with 3.3 mol/l KCl, E'

(vs SHE)

AgCl

9-11

9. T echnical Information

9.10 Wetted Part Materials of Sensors

• General pH Sensors

Polypropylene resin (sensor body, protective cover) Glass (glass electrode, temperature element protective tube) Ceramics (liquid junction) Silicon rubber (sensor seal)

- When cable is immersed (KCl replenish-free type) Rigid polyethylene (sensor grip) PVC (sensor cable) Ethylene propylene rubber (sensor grip, cable connection)

• Needle type pH sensor

Glass (sensor)

• T est tube size pH sensor

Glass (sensor)

• ORP sensor

Polypropylene resin (sensor body, protective cover) Platinum (electrode) Glass (glass electrode, temperature element protective tube) Ceramic (liquid junction) Silicon rubber (sensor seal)

9.11 References

• JIS Z8802-1984, Methods for Determination of pH of Aqueous Solutions

• Moore, W. J., Basic Physical Chemistry, Prentice-Hall, Inc., U.S.A. 1983

• Donald, Andrzej, Julian, Electrochemistry for chemists 2nd Ed., Maruzen 2003

• Bates, R. G., Determination of pH: theory and practice 2nd Ed., John Wiley & Sons, Inc.,1973

9-12

IM 12B03D02-01E

Appendix

Key-Operation Flow Chart (for reference)

Typical screens are shown. Refer to the corresponding section in the body of the manual for details.

Appendix

d When turn on power

POWER

First time used, or after replace batteries

F/ENT

Toggle display type

MEAS

d Temporary hold

or or

HOLD

MEAS

IM 12B03D02-01E

F/ENT

d Storing data

DATA

MEAS

F/ENT

T01.EPS

Appendix

d Function Mode

Display stored data

Manual temperature

setting

Set measurement

unit

F/ENT

DATA

F/ENTF/ENT

F/ENT F/ENT

F/ENT

T02.EPS

IM 12B03D02-01E

d Function Mode

Delete all stored data

Date setting

Time setting

Alarm time setting

Appendix

Set Auto Power Off time

F/ENT

d Switching to Function Mode

Measurement status

F/ENT

d Reverting to Measurement Mode

Measurement status

F/ENT

IM 12B03D02-01E

MEAS

T03.EPS

Appendix

d Function Mode

Set beep on/off

Standard solution

setting

Initialize calibration

parameters

Set temperature unit

F/ENT

d Function Mode

Check version

number

F/ENT

Defrag memory

F/ENT

T04.EPS

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d Calibration

Automatic calibration & Manual calibration

Measurement

status

Auto calibration

in progress

(2-point calibration)

Auto calibration

is complete

Appendix

CAL

Manual calibration

F/ENT

Prompting

F/ENT F/ENT

Automatic calibration for needle type or test tube size pH sensor

Measurement

status

Temperature set on 'M.tP' panel

Auto calibration

CAL

25.08C fixed

F/ENT

Input of standard

solution temperature

Standard solution temperature

Auto calibration

F/ENT

in progress

Manual calibration

is complete

F/ENT

Auto calibration

is complete

Temperature set on 'M.tP' panel

T05.EPS

IM 12B03D02-01E

Appendix

IM 12B03D02-01E

MSDS (Material Safety Data Sheet)

The contents are provided for informative purposes only and no guarantee is given to the accuracy.

The information, such as manufacturers, in the data sheets is subject to change without notice.

Item MSDS Product Name Page Standard pH4 standard solution Phthalate standard solution MSDS-2 to 4 accessories pH7 standard solution Neutral phosphate standard splution MSDS-5 to 8 KCl filling solution Potassium chloride aqueous MSDS-12 to 15 Options pH9 standard solution Borate solution MSDS-9 to 11 Spare parts Quinhydrone reagent Quinhydrone MSDS-16 to 18 + Potassium hydrogen phthalate MSDS-19 to 21 + Potassium chloride MSDS-13 to 15

MSDS

T01.EPS

IM 12B03D02-01E

MSDS-1

MSDS

MSDS-2

IM 12B03D02-01E

MSDS

IM 12B03D02-01E

MSDS-3

MSDS

MSDS-4

IM 12B03D02-01E

MSDS

IM 12B03D02-01E

MSDS-5

MSDS

MSDS-6

IM 12B03D02-01E

MSDS

IM 12B03D02-01E

MSDS-7

MSDS

MSDS-8

IM 12B03D02-01E

MSDS

IM 12B03D02-01E

MSDS-9

MSDS

MSDS-10

IM 12B03D02-01E

MSDS

IM 12B03D02-01E

MSDS-11

MSDS

MSDS-12

IM 12B03D02-01E

MSDS

IM 12B03D02-01E

MSDS-13

MSDS

MSDS-14

IM 12B03D02-01E

MSDS

IM 12B03D02-01E

MSDS-15

Yokogawa PH72 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Preface

1. Outline

1.1 Features

1.2 Specifications

1.3 When You Receive the PH72 Meter Package

1.4 PH72 Meter Kit

1.5 PH72 Meter — Part Names and Functions

1.6 Sensors — Types, Part Names and Functions

1.7 Options (Available Separately)

1.8 Spare Parts

2. Preparation

2.1 Installing the Batteries

2.2 Connecting the Sensor Cable

2.3 Setting the Date and Time

2.4 Selecting pH or ORP Measurement

2.5 Wetting Cap

2.6 Manual Temperature Setting

2.7 pH Calibration

3. Measurement

3.1 Precautions

3.2 Measurement Procedures

3.3 Measurement Display Panel

3.4 Saving a Measured Value

4. Calibration

4.1 Automatic Calibration

4.2 Manual Calibration

5. Keypad and Display Functions

5.1 Keypad Functions

5.2 Display Items

5.3 Function Mode

6. Maintenance

6.1 For Optimum Meter Performance

6.2 pH Electrode Cleaning

6.3 Sensor Replacement

6.4 Rehydrating the Glass Electrode

6.5 Replenishing the Electrode with Filling Solution (KCl solution)

6.6 Cleaning and Drying Connectors

6.7 Storage and O-ring/Gasket Replacement

7. Troubleshooting

7.1 Causes of Abnormal Readings and Errors

7.2 Error Messages, Possible Causes, and Corrective Actions

7.3 Causes of Abnormal Measured Values

7.4 Other Conditions

8. ORP Meter

8.1 ORP Measurement

8.2 Maintenance of ORP Sensors

8.3 Checking the ORP Sensor

9. T echnical Information

9.1 Measurement Principle of pH Meter (Glass Electrode Method)

9.2 Relationship between EMF of Glass Membrane and pH Value

9.3 Temperature Compensation

9.4 The Asymmetry Potential

9.5 The Alkaline Error

9.6 The Acid Error

9.7 Calibration Calculation

9.8 ORP (Oxidation-Reduction Potential)

9.9 Reference Electrode

9.10 Wetted Part Materials of Sensors

9.11 References

Appendix

MSDS (Material Safety Data Sheet)