Extech Instruments PH220 Manual de usuario

User Guide

Waterproof Palm pH Meter

Model PH220

7.00

PH220-EU-EN V3.2 8/12

Introduction

Congratulations on your purchase of the Extech PH220 waterproof pH/mV meter. This

microprocessor-based device with tactile push-buttons is battery operated and ideal for field use.

The PH220 simultaneously displays pH and temperature. The rubber holster which protects the

meter has a magnetic backing for convenient mounting. The built-in memory (25 readings) allows

STORE, RECALL, and CLEAR functionality. Careful use of this meter will provide years of reliable

service.

Specifications

Range (Resolution) Accuracy

Temperature

32 to 212oF (<100o;1 o >100o)

0 to 100oC (0.1°<100°;1°>100°)

± 1.0oF

± 0.5oC

0.00 to 14.00pH (0.01pH) ± 0.02pH

pH Note 1: Accuracy does not include pH buffer temperature

coefficient

Note 2: Accuracy specified from 0.02pH to 13.98pH

Temperature Compensation 32 to 212oF (0-100oC) Automatic ‘ATC’

Power 9 volt alkaline battery

Display Dual LCD display for simultaneous pH and temperature

readings

Over-range or open indication Displays "HHH" for over-range or open input conditions

Displays “LLL” for under-range

pH Calibration points 4.00, 7.00, 10.00 (1, 2, or 3 point calibration can be

performed)

Auto Power OFF 10 minutes from last key-press (can be disabled)

Low Battery Indication Fill bars in the battery display icon represent battery

power status. The fewer the bars, the weaker the battery

power.

Dimensions / Weight 4.25 x 3.00 x 1.18" (108 x 75 x 30mm) / 4.8 oz. (135g)

Accessories supplied with kit Battery, suction cup holder, clip holder, stick electrode for

model PH220-S, standard electrode with 39” cable for model

PH220-C.

PH220-EU-EN V3.2 8/12

Meter Description

1. Battery Compartment (under holster)

2. Rubber Holster

3. LCD Display

4. Function buttons

5. Electrode input

Basic Display Description

1. Measurement value

2. Battery status

3. Units of measure

4. Temperature units

5. Solution temperature

Note that there are other more

specialized displays that appear on the LCD that have not been included in this basic operation

display description. Other display icons are used and are discussed in the appropriate sections of

this manual.

Order of Operations

1. Calibrate the instrument as described later in this manual.

2. Configure the meter to display in the desired units of measure for temperature (oC or oF). This is

included as a step in the pH measurement instructions.

3. Pay close attention to detail, step by step instructions, and electrode cleaning/rinsing

recommendations. Slight deviations in test procedures and test habits can have a significant

effect on test results.

7.00

PH220-EU-EN V3.2 8/12

Calibration (pH)

The sensitivity of a pH electrode degrades over time, it is very important to frequently calibrate the

meter to the electrode. pH electrodes can be thought of as batteries in that they run down with time

and use.

Calibration is performed using standard buffer solutions at room temperature (78°F, 25°C). Buffer

solutions are solutions of a known pH that have the useful property of resisting changes in pH.

These can be purchased already mixed or in capsule form and are usually available in three pH

values, pH 4.00, pH 7.00 and pH 10.00.

Calibration is always performed using the pH 7.00 buffer first, followed by a second calibration.

Select pH 4 buffer for the second calibration if typical measurements will be less than pH7 or use a

pH 10 buffer if typical measurements will be greater than ph 7.

In order to obtain the most accurate results possible, a pH meter should be calibrated at

least once each day.

pH Calibration Procedure

1. Place the electrode into a 7.00 pH buffer solution. Press and hold the CAL button until “CAL”

appears in the display.

2. The instrument automatically recognizes the solution and calibrates to that value. Note that if

the solution is off by more than 1 pH unit from the 4, 7, or 10 pH buffer, or if the electrode slope

is low, the instrument will assume an error and abort the calibration (End will be displayed, and

the unit will return to the normal measurement mode.)

3. During calibration, the pH reading flashes on the main display.

4. When calibration is complete, the instrument automatically displays ‘SA’ followed by ‘End’ and

then returns to the normal operation mode.

5. For a two or three point calibration, repeat steps 1-4. When doing a 2 or 3 point calibration,

calibrate with pH 7 buffer first, then follow with pH 4 and/or pH 10.

CAL Reminder Display

When in pH measurement mode, the CAL icon will appear if a calibration has not been performed

after 15 on/off cycles of the instrument. The CAL display is simply a reminder and will turn off when

the pH electrode is recalibrated. The reminder does not affect function in any way.

PH220-EU-EN V3.2 8/12

Measuring pH

Electrodes should always be rinsed before and between samples with

distilled or DI (de-ionized) water to remove all traces of storage solution,

process media, or previous test solution.

1. Connect the pH electrode to the meter.

2. Turn the meter on using the on/off button . Wait for the self test (‘SLF tSt’) to finish.

3. Use the MODE button to select pH mode. The unit of measure appears on the LCD.

4. To change the unit of measure for temperature (oC to oF or oF to oC), press and hold the MODE

button for 3 seconds. The LCD reflects the current unit of measure.

5. Rinse the electrode with distilled or deionized water.

6. Place the electrode in the solution. Allow 30 seconds for the electrode/ATC to reach thermal

equilibrium with the buffer solution.

7. After the measurement stabilizes, view the pH reading on the main display. An out of range

reading is indicated by the display icon ‘HHH’. Note that ‘HHH’ will also display when the

electrode is disconnected from the meter.

8. When the test is complete rinse the electrode with distilled or deionized water.

Automatic Temperature Compensation (ATC)

The millivolt output of a pH electrode varies with temperature, and for this reason the meter must

compensate for these variations to obtain accurate measurements. The PH220 automatically

compensates for solution temperature changes with the electrode’s built-in thermometer. The

temperature compensation is active when the solution temperature deviates from room temperature.

The temperature of a solution is displayed on the lower LCD line of the instrument.

Automatic Power OFF

To conserve battery power, the instrument automatically shuts off after 10 minutes of inactivity. To

disable or enable this feature, follow the steps below:

To disable: With the power on, press and hold the on/off button for 2 seconds (oFF and

AtP will display). The Auto Power OFF feature is now disabled.

To enable: With the power on, press and hold the on/off button for 2 seconds (on and AtP will

display). The Auto Power OFF feature is now enabled.

Each time the meter is turned off the Auto power OFF feature is set to the enabled mode.

PH220-EU-EN V3.2 8/12

Storing and Recalling Readings

This instrument has the ability to store up to 25 measurement readings. At a later time the readings

can be recalled and viewed. Readings are saved even after the instrument has been turned off.

STORE Readings

The steps below cover the STORE process in detail:

1. Take a measurement as described earlier in this manual.

2. Momentarily press the STORE/RECALL button to save the reading. The reading will be held

on the display (the HOLD and STORE icons will appear). In addition, the storage location (1 to

25) will briefly appear on the lower portion of the LCD.

3. Note: The temperature reading associated with the pH reading is also saved.

4. Press the STORE/RECALL button again to release the ‘hold’ feature. The instrument will then

return to normal operation.

5. Note that when all 25 storage locations are filled the instrument begins writing over the

previously stored data.

RECALL Readings

The steps below cover the RECALL process in detail:

1. Press and hold the STORE/RECALL button until a number appears on the main display. This

number is the storage location for the most recent reading.

2. The number will switch off after 1 second and the stored reading will appear. The RECALL icon

will appear and remain on the entire time the recall mode is accessed.

3. While in the RECALL mode, use the STORE/RECALL button to scroll through the stored

readings. The most recent readings will show first (LAST IN – FIRST OUT).

4. Press and hold the STORE/RECALL button until the END display appears. Release the button

and the instrument will return to normal operation mode.

5. Note that if there are no readings in memory, the display will show END when the user

attempts to access the RECALL mode.

ERASE Readings

The steps below cover the ERASE (CLEAR) process in detail:

1. Press and hold STORE/RECALL and the CAL buttons simultaneously for 4 seconds.

2. The ‘CLr’ display will appear indicating that all readings have been erased.

3. Release the buttons to return to normal operation mode.

Temperature Offset Adjustment

Applications may arise where it is desirable to offset the instrument’s temperature display. This

instrument allows a temperature display offset adjustment of ±9oF (±5oC). To do so, follow the steps

below:

1. Press and hold the CAL, MODE, and STORE/RECALL buttons simultaneously for 6 seconds.

2. The main display will indicate the current offset. The lower display will show ‘t_O’.

3. Use the CAL button to decrease the offset value and the MODE button to increase it.

4. Press and hold the STORE/RECALL button for 2 seconds to exit this mode. The instrument

will display ‘SA’ (save) and ‘END’ before returning to the normal operation mode.

5. The temperature display will now indicate the actual temperature ± the offset value.

PH220-EU-EN V3.2 8/12

Battery Replacement

The 9 volt alkaline battery that powers the instrument requires replacing when all battery icon ‘fill

bars’ are depleted. To replace the battery follow the steps below:

1. Disconnect the electrode from the instrument.

2. Remove the instrument’s protective jacket by pulling it over the top of the meter (ensure that

the electrode is disconnected).

3. Pry the battery compartment up from the top of the meter using a screwdriver or coin at one

of the two indentations (see diagram).

4. Replace the 9V battery.

5. Insert the battery compartment into the instrument until the compartment is flush with the top

of the instrument. The compartment can only be fully inserted in one direction and the

battery compartment is labeled as to the polarity orientation of the battery.

6. Replace the protective holster.

PH220-EU-EN V3.2 8/12

Electrode Maintenance and Troubleshooting

Most pH measurement difficulties are caused by the electrode. Careful handling and proper storage of

the electrode will increase measurement accuracy and electrode life.

Electrodes should be rinsed to remove all traces of storage solution, process medium, or previous test

solution.

Electrode Storage

The electrode should be stored in a soaker bottle or wetting cap filled with pH4 buffer. Never store

an electrode in distilled or deionized water as this will cause migration of the fill solution from the

electrode.

Electrode Cleaning

The type of electrode coating that occurs over time will determine the cleaning method. Soft

coatings can be removed by vigorous stirring or by using a squirt bottle. Organic chemical coating

(hard coatings) should be chemically removed. Only in extreme cases should the bulb be cleaned

mechanically.

Troubleshooting an Electrode

Symptom Cause Recommendation

Clogged Junction Soak in 4.07 M Potassium Chloride (KCl) @

60oC for 30 minutes.

Strong Alkaline measurement Soak in 0.1 M HCL overnight.

Deteriorated Gel layer Replace electrode.

Protein coating on electrode

surface

Soak in 1 gm Pepsin dissolved in 100ml of 0.1

m HCL for 30 minutes or as needed.

Oil, paint, dyes, suspended solids

etc. are on sensor

Rinse electrode alternately with a materials

solvent and a buffer 7.00.

Organic solvents are coating the

sensor

Organic mole fraction has to be less than 50%

to assure reasonable readings. Limit time of

measurement. Keep probe in the 7.0 buffer

between readings.

Long response time or

reading drift

Dehydrated membrane Read solution for dry bulb below:

Dry Bulb Long term storage without wetting Soak electrode tip in wetting cap filled with 1ml

7.00 buffer for 24 to 48 hours

Static Charge Wiping electrodes Rinse electrode in 7.0 buffer and blot. Do no

wipe electrode.

Same readings in different

buffers and samples

Cracked or broken bulb Replace electrode. Use bulb guard. Avoid

plunging electrode to bottom of container and

spinning bars. Wetting cap will protect bulb

between tests.

Erratic LCD display Samples have low ionic strength

(lacks salt); e.g. distilled, de-

ionized, boiled, lake water (high

pressure)

For each 50 ml of sample add 1 drop (50uL) of

SAT. KCl (No alteration in pH will occur using

inert KCl).

Calibration and Repair Services

Extech offers repair and calibration services for the products we sell. Extech also provides NIST

certification for most products. Call the Customer Service Department for information on calibration

services available for this product. Extech recommends that annual calibrations be performed to

verify meter performance and accuracy.

ISO-9001 Certified

www.extech.com

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