Hanna Instruments HI 255 User Manual

Instruction Manual

HI 255

Multiparameter

pH/mV/ºC

EC/TDS/NaCl Bench Meter

www.hannainst.com

Dear Customer, Thank you for choosing a Hanna Instruments product. Please read this instruction manual carefully before using the instrument. This manual will provide you with the necessary information for correct use of

the instrument, as well as a precise idea of its versatility. If you need additional technical information, do not hesitate to e-mail us at

tech@hannainst.com or turn to the back cover for our worldwide contact list.

WARRANTY

HI 255 is guaranteed for two years against defects in workmanship and materials when used for its intended purpose and maintained according to instructions. Electrodes and probes are guaranteed for six months. This warranty is limited to repair or replacement free of charge.

Damage due to accidents, misuse, tampering or lack of prescribed maintenance is not covered.

If service is required, contact the dealer from whom you purchased the instrument. If under warranty, report the model number, date of purchase, serial number and the nature of the problem. If the repair is not covered by the warranty, you will be notified of the charges incurred. If the instrument is to be returned to Hanna Instruments, first obtain a Returned Goods Authorization number from the Technical Service department and then send it with shipping costs prepaid. When shipping any instrument, make sure it is properly packed for complete protection.

TABLE OF CONTENTS

WARRANTY ................................................................................................................... 2

PRELIMINARY EXAMINATION ........................................................................................... 3

GENERAL DESCRIPTION .................................................................................................... 3

FUNCTIONAL DESCRIPTION ............................................................................................. 4

HI 255 SPECIFICATIONS .................................................................................................. 5

OPERATIONAL GUIDE ....................................................................................................... 7

AUTORANGING ................................................................................................................ 11

pH CALIBRATION ................................................................................................................ 12

RELATIVE mV CALIBRATION .......................................................................................... 15

ECS/TDS CALIBRATION ................................................................................................... 16

NaCl CALIBRATION .......................................................................................................18

GOOD LABORATORY PRACTICE (GLP) .....................................................................................19

LOGGING FUNCTION .......................................................................................................25

SETUP .................................................................................................................................31

TEMPERATURE CALIBRATION (FOR TECHNICAL PERSONNEL ONLY) .................................36

mV CALIBRATION (FOR TECHNICAL PERSONNEL ONLY) .............................................. 38

PC INTERFACE ............................................................................................................... 39

pH VALUES AT DIFFERENT TEMPERATURES .................................................................... 41

CONDUCTIVITY VERSUS TEMPERATURE CHART ................................................................ 42

ELECTRODE CONDITIONING & MAINTENANCE ................................................................. 43

TROUBLESHOOTING GUIDE ........................................................................................... 46

TEMPERATURE CORRELATION FOR pH SENSITIVE GLASS .............................................47

ACCESSORIES .................................................................................................................... 48

PRELIMINARY EXAMINATION

Remove the instrument from the packing material and examine it carefully to make sure that no damage has occurred during shipping. If there is any damage, notify your Dealer or the nearest Hanna Customer Service Center.

Each instrument is supplied with:

 HI 1131B Glass-body Combination pH Electrode with 1 m (3.3') Cable  HI 76310 Conductivity / TDS probe  HI 7662 Temperature Probe  HI 76404 Electrode Holder  pH 4.01 & 7.01 Buffer Solutions (20 mL each)  HI 7071S Electrolyte Solution  12VDC Power Adapter  Instruction Manual

Note: Save all packing material until you are sure that the instrument

functions correctly. All defective items must be returned in the original packing with the supplied accessories.

GENERAL DESCRIPTION

The HANNA HI 255 is a logging microprocessor-based pH, ORP, Conductivity (EC), TDS, NaCl and Temperature bench meter. Relative mV feature is also provided.

The pH measurements are compensated for temperature effect manually or automatically with the HI 7662 temperature probe.

pH Calibration is possible in up to three points, using five memorized buffers (4.01, 6.86, 7.01, 9.18 and 10.01).

The autoranging feature of the EC and TDS ranges automatically sets the instrument to the scale with the highest possible resolution.

The conductivity measurements are compensated for temperature effect manually or automatically with the temperature sensor inside the conductivity probe. It is also possible to disable the temperature compensation and measure the actual conductivity.

The temperature coefficient is user selectable. The GLP feature provides a guarantee of data consistency. An alarm time-out is available to alert the user that too much time elapsed

since last pH calibration. The instrument can store data in memory at the users request for later

retrieval.

Front Panel

Primary LCD

Secondary LCD

13 14 15

Rear Panel

POWER

12VDC

INPUT TEMP

RS232

PROBE

ALT FunctionsFunctions

RCL

LOG

ALT

SET

LOCK/CLR

ATC

MODE

RANGE

GLP

CFM

CAL

pH/mV & EC/TDS/NaCl

HI 255 Combined Meter

TC Factor

ATC

Select Temperature Compensation

Recall Log Data

RCL

SET

Set Parameters

Select Measure Mode

MODE

Confirm/GLPData

CFM/GLP

Calibration

CAL

Change Parameter Value

StoreLog Data

LOG

Lock Current Range Clear Calibration

LOCK/CLR

Select Measure Unit Scroll Log Data

RANGE

REF

BUFFER pH

INTVDATETIME%

ppm

BUF

WRONG

READY

CFM

NaCl

pHmVg / lLOGCAL

FUNCTIONAL DESCRIPTION

1) Liquid Crystal Display (LCD).

2) CFM/GLP key, to confirm different values or to display Good Laboratory

Practice information.

3) CAL key, to enter and exit/escape calibration mode.

4) key, to manually decrease temperature value or other parameters.

ATC key (alternate function), to select EC temperature compensation mode.

5) key, to manually increase temperature value or other parameters.

TC key (alternate function), to view the temperature coefficient value.

6) LOG key, to store measured data. RCL key (alternate function), to enter/exit recall mode.

7) ALT key, to select alternate key function.

8) LOCK/CLR key, to freeze current EC range on the LCD or to clear pH calibration parameters.

SET key (alternate function), to enter/exit setup mode.

9) RANGE key, to switch measurement unit pH/mV/EC or focused data. MODE key (alternate function), to select measurement mode/pH resolution.

10) ON/OFF switch.

11) Power supply socket.

12) Conductivity socket.

13) BNC electrode connector.

14) Electrode reference socket.

15) Temperature probe socket.

16) RS232 serial communication connector.

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SPECIFICATIONS (cont.)

OPERATIONAL GUIDE

POWER CONNECTION

Plug the 12 VDC adapter into the power supply socket. Note: This instrument uses non volatile memory to retain the calibration

parameters and all other settings, even when unplugged.

Note: Make sure a fuse protects the main line.

ELECTRODE AND PROBE CONNECTIONS

For pH or ORP measurements connect an electrode with internal reference to the BNC connector on the back of the instrument.

For electrodes with a separate reference connect the electrodes BNC to the BNC connector and the reference electrode plug to the reference socket.

For temperature measurements and automatic temperature compensation connect the temperature probe to the appropriate socket.

For EC/TDS measurements connect the probe to the 7-pin connector. Make sure the probe sleeve is properly inserted.

INSTRUMENT START-UP

 Turn the instrument on by pressing the ON/OFF switch.  All LCD tags are displayed and a beep is sounded while

the instrument performs a self test.

Note: • The instrument starts in the same range and mode as it was at

power off.

• The RANGE key toggles between pH, mV and EC ranges.

• The ALT&MODE keys changes the displayed information for the

selected range.

pH MEASUREMENTS

Make sure the instrument has been calibrated before taking pH measurements.

 Press RANGE to enter pH range. Note: To select pH resolution press the ALT&MODE keys.

 Submerge the electrode tip and the temperature probe

approximately 4 cm (1½) into the sample to be tested and stir gently. Allow time for the electrode to stabilize.

 The pH is displayed on the primary LCD and the temperature on the

4cm

(1 )

1/2”

secondary LCD.

 If the reading is out of range, the closest full-scale value will be displayed

blinking on the primary LCD.

If measurements are taken successively in different samples, it is recommended to rinse the electrode thoroughly with deionized water or tap water and then with some of the next sample to prevent cross-contamination.

The pH reading is affected by temperature. In order to measure the pH accurately, the temperature effect must be compensated for. To use the Automatic Temperature Compensation feature, connect and submerge the

HI 7662 temperature probe into the sample as close as possible to the electrode and wait for a few seconds.

If the temperature of the sample is known, manual compensation can be performed by disconnecting the temperature probe.

The display will then show the default temperature of 25 ºC or the last temperature reading with the ºC tag blinking.

The temperature can now be adjusted with the ARROW keys (from 10.0 ºC to 120.0 ºC).

mV/ORP MEASUREMENTS

An optional ORP electrode must be used to perform ORP measurements (see Accessories).

Oxidation-Reduction Potential (REDOX) measurements provide the quantification of the oxidizing or reducing power of the tested sample.

To correctly perform a REDOX measurement, the surface of the ORP electrode must be clean and smooth.

 Press RANGE to enter mV range.  Submerge the tip of the ORP electrode (4 cm/1½) into

the sample to be tested and allow a few seconds for the reading to stabilize.

 The instrument displays the mV reading on the primary LCD and the

temperature on the secondary LCD line.

 If the reading is out of range, the closest full-scale value will be displayed

blinking on the primary LCD.

RELATIVE mV MEASUREMENTS

Press the ALT&MODE keys simultaneously while in mV range. The rEL message will be displayed on the secondary LCD line for about one second and the mV tag will blink. After one second the temperature will be displayed on the secondary LCD line.

The reading displayed by the instrument is equal to the difference between the current mV input value and relative mV offset established in the relative mV calibration.

CONDUCTIVITY MEASUREMENTS

Connect the conductivity probe to the instrument.  Press RANGE to enter conductivity measurement range (EC).  Immerse the probe into the solution to be tested. The sleeve

holes must be completely submerged. Tap the probe repeatedly to remove any air bubbles that may be trapped inside the sleeve.

The conductivity value will be displayed on the primary LCD and the temperature on the secondary LCD line.

 If the reading is out of range, the full-scale value (200.0 for Mtc/Atc mode

or 500.0 for actual conductivity) will be displayed blinking.

 If LOCK was pressed to freeze the LCD range and the reading went out of

ALT

ATC

range, the full-scale value of the frozen range will be displayed blinking.

The EC reading is affected by temperature. Three options of compensating temperature are available, on EC measurement

mode. Note: The compensation is referenced at the selected reference temperature

(see SETUP for details, page 31).

Automatic (Atc): The EC probe has a built-in temperature sensor; the temperature value is used to automatically compensate the EC/TDS reading (from 0.0  60.0 ºC).

Manual (Mtc): The temperature value, shown on the secondary LCD, can be manually set with the ARROW keys. The ºC tag blinks when this option is active.

No Compensation (notc): The temperature value is displayed, but is not taken into account and ºC tag blinks with a higher frequency. The reading displayed on the primary LCD is the actual EC or TDS value. To select the desired option, press the ALT&ATC keys until the option is displayed on the LCD.

Note: • The default compensation mode is Atc.

• If no temperature probe detected, Atc mode can not be selected

and the instrument displays ---- on the secondary LCD.

If temperature compensation is active, measurements are compensated using the temperature coefficient (default value 1.90 %/ºC). To change the temperature coefficient, enter the setup mode and select the tc item (see SETUP for details, page 31). The current temperature coefficient can be quickly viewed by pressing the ALT&TC keys. The value is briefly displayed on the secondary LCD.

 If the temperature reading is out of 0.0  60.0 ºC interval and Atc option is

selected, the ºC tag will blink and the closest interval limit will be displayed.

 Press the ARROW keys to change the displayed temperature value. This

value is used to compensate the EC/TDS reading.

TDS MEASUREMENTS

Press the ALT&MODE keys while in EC range. The instrument will switch to TDS measuring range. A TDS reading will be displayed on the primary LCD and the temperature reading on the secondary LCD.

 If the reading is out of range, the full-scale value (100.0 for Mtc/Atc mode

or 400.0 for actual TDS) will be displayed blinking.

 If LOCK was pressed to freeze the LCD range and the reading went out of

range, the full-scale value of the frozen range will be displayed blinking.

NaCl MEASUREMENTS

Press the ALT&MODE keys while in EC range until NaCl is displayed on the LCD. The instrument will display the NaCl reading on the primary LCD and the temperature reading on the secondary LCD line.

 If the reading is out of range, the full-scale value (400.0%) will be

displayed blinking.

TEMPERATURE MEASUREMENTS

To take temperature measurements while the instrument is in pH/ORP range, connect the HI 7662 temperature probe to the appropriate socket.

Immerse the temperature probe into the sample and allow the reading on the secondary LCD to stabilize.

For EC/TDS/NaCl range, the HI 76310 probe has a built-in temperature sensor. Note:  If the instrument is in pH/ORP range and the HI7662 temperature

probe is not connected, the ºC tag will blink (manual compensation) even if EC probe is connected.

AUTORANGING

The EC and TDS scales are autoranging. The meter automatically sets the scale with the highest possible resolution.

By pressing LOCK, the autoranging feature is disabled and the current range is frozen on the LCD. The Auto Off (autoranging disabled) tags will be displayed on the LCD for a few seconds. To restore the autoranging option, press LOCK again. The Auto On (autoranging enabled) tags will be displayed on the LCD for a few seconds.

Note: Autoranging is automatically restored if the range is changed, if the setup or

calibration modes are entered and if the meter is turned off and back on again.

pH CALIBRATION

BUF

BUFFER pH

BUF

pHCAL

Calibrate the instrument frequently, especially if high accuracy is required. The instrument should be recalibrated :  Whenever the pH electrode is replaced.  At least once a week.  After testing aggressive chemicals.  If CAL INTV tags are blinking during measurement.

Every time you calibrate the instrument use fresh buffers and perform an electrode Cleaning Procedure (see page 45).

PREPARATION

Pour small quantities of the buffer solutions into clean beakers. If possible, use plastic or glass beakers to minimize any EMC interferences.

For accurate calibration and to minimize cross-contamination, use two beakers for each buffer solution. One for rinsing the electrode and one for calibration.

If you are measuring in the acidic range, use pH 7.01or 6.86 as first buffer and pH 4.01 as second buffer. If you are measuring in the alkaline range, use pH

7.01 or 6.86 as first buffer and pH 10.01 or 9.18 as second buffer.

PROCEDURE

Calibration has a choice of 5 memorized buffers: pH 4.01, 6.86, 7.01, 9.18 and 10.01.

It is recommended to perform a two or three-point calibration. However, the instrument also allows a one-point calibration, as described on page 14.

Select pH range by pressing RANGE.

THREE-POINT CALIBRATION

 Immerse the pH electrode and the temperature probe

approximately 4 cm (1½) into a buffer solution of your choice (pH 4.01, 6.86, 7.01, 9.18 or 10.01) and stir gently. The temperature probe should be close to the pH electrode.

 Press CAL. The CAL and 

the 7.01 buffer will be displayed on the secondary LCD.

 tags will appear and

 If necessary, press the ARROW keys to select a different buffer value.

 The   tag will blink on the LCD until the reading is

BUFFER pH

BUF

pHCAL

stable.

 When the reading is stable and close to the selected buffer,

READY tag will be displayed and CFM tag will blink.

 Press CFM to confirm calibration.  The calibrated value will be displayed on the primary LCD

and the second expected buffer value on the secondary LCD line.

Note: The instrument will automatically skip the buffer used for the first point.

It also skips 6.86 if 7.01 buffer was used and viceversa. Likewise, it will skip 9.18 if 10.01 buffer was used and viceversa.

 After the first calibration point is confirmed, immerse the pH electrode and

the temperature probe approximately 4 cm (1½) into the second buffer solution and stir gently. The temperature probe should be close to the pH electrode.

 If necessary, press the ARROW keys to select a different buffer value.  The   tag will blink on the LCD until the reading is

stable.

 When the reading is stable and close to the selected buffer,

READY tag will be displayed and CFM tag will blink.

• Press CFM to confirm calibration.

• The calibrated value will be displayed on the primary LCD

and the third expected buffer value on the secondary LCD line.

Note: The instrument will automatically skip the buffer used for the first and

second calibration point.

 After the second calibration point is confirmed, immerse the pH electrode

and the temperature probe approximately 4 cm (1½) into the third buffer solution and stir gently. The temperature probe should be close to the pH electrode.

 If necessary, press the ARROW keys to select a different buffer value.  The   tag will blink on the LCD until the reading is

stable.

 When the reading is stable and close to the selected buffer,

READY tag will be displayed and CFM tag will blink.

• Press CFM to confirm calibration.

 The instrument stores the calibration value and returns

to normal measurement mode.

Note:  If the value measured by the instrument is not

BUF

close to the selected buffer, WRONG 



and WRONG   tags will blink alternately. In this case, check if the correct buffer has been used or regenerate the electrode by following the Cleaning Procedure (see page 45). If necessary, change the buffer or the electrode.

 If WRONG, Buffer pH tags and Old tag on secondary LCD are

displayed blinking, an inconsistency between new and previous (old) calibration is detected. Clear calibration parameters by pressing LOCK/CLR and proceed with calibration from the current calibration point (the instrument will keep all confirmed values during current calibration).

 If LOCK/CLR is pressed at the first calibration point, the instru-

ment clears all calibration parameters and returns to measurement mode.

 The WRONG tag and temperature value are displayed blinking

if temperature reading is out of the defined temperature range of the buffer. Calibration cannot be confirmed in this situation.

 Press RANGE to display the temperature reading

on the LCD during calibration.

TWO-POINT CALIBRATION

 Proceed as described in Three-point calibration section.  Press CAL after the second calibration point was confirmed. The instrument will return to measurement mode and will memorize the

two-point calibration data.

ONE-POINT CALIBRATION

 Proceed as described in Three-point calibration section.  Press CAL after the first calibration point was confirmed. The instrument will return to measurement mode and will memorize the

one-point calibration data. Note: Calibration parameters are evaluated taking in consideration the new

values for the confirmed buffers in current calibration and the old values, if existing, for the other buffers. To clear old calibration values, press LOCK/CLR before exiting calibration.

RELATIVE mV CALIBRATION

 Press CAL when the instrument is in RELATIVE mV measurement mode.

The mV and   tags will blink. Absolute mV is displayed on the primary LCD and AbS message is displayed on the secondary LCD.

 When the reading is stable and inside the offset window (±200 0 mV), the

instrument asks for confirmation.

 If the reading is out of the offset window, WRONG tag will be displayed.  Press CFM to confirm absolute value. The instrument will display 0.0 mV

on the primary LCD and rEL message on the secondary LCD line. In this moment the relative mV offset is equal to absolute mV reading.

 Use the ARROW keys if you want to change the displayed value.  Press CFM to confirm relative mV calibration. The instrument will return to

measurement mode.

EC/TDS CALIBRATION

BUF

CAL

BUF

CAL

READY

CFM

EC calibration is a one-point procedure. Selectable calibration points are 0.00 µS for offset and 84.0 µS, 1413 µS, 5.00 mS, 12.88 mS, 80.0 mS, 111.8 mS for slope.

Rinse the probe with calibration solution or deionized water. Immerse the probe into the solution. The sleeve holes must be completely submerged. Tap the probe repeatedly to remove any air bubbles that may be trapped inside the sleeve. To enter EC calibration, select the EC range and press CAL.

Note: TDS reading is automatically derived from the EC

reading and no specific calibration for TDS is needed. Pressing CAL when TDS range is selected has no effect.

For zero calibration, just leave the dry probe in the air. This calibration is performed in order to correct the reading around 0.00 µS point. The slope is evaluated when the calibration is performed in any other point.

The BUF and CAL tags are displayed. The primary LCD will display the EC reading. The secondary LCD will display the buffer value. The   and ~ tags will blink.

Select the desired value with the ARROW keys, if necessary.

When the reading is stable, READY tag is displayed and CFM tag starts blinking on the LCD, asking for confirmation.

Press CFM to confirm calibration. The instrument stores the calibration value and returns to

measurement mode. Note: • If the uncalibrated reading is too far from the expected value, the

WRONG and   tags will blink. Calibration can not be confirmed.

In this case check if the correct buffer has been used or clean the probe

by following the Cleaning Procedure (see page 45).

• If the meter is in Atc mode and the buffer temperature is out of

WRONG

CAL

0.0  60.0 ºC interval, WRONG ºC tags and the temperature will be displayed blinking.

• For best results choose an EC buffer value close to the sample to be

measured.

• In order to minimize any EMC interference, use plastic or glass

beakers.

• It is possible to set the cell constant value directly, without following

the calibration procedure. To set the cell constant, enter SETUP mode and select CEL (see SETUP for details, page 31).

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