Hanna Instruments HI 255 User manual

1
Instruction Manual
HI 255
Multiparameter
pH/mV/ºC
EC/TDS/NaCl
Bench Meter
www.hannainst.com

2
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
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 Authori-
zation 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.
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
[email protected] or turn to the back cover for our worldwide contact list.

3
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.
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.
GENERAL DESCRIPTION

4
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 clearpH
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.
FUNCTIONAL DESCRIPTION
Front Panel
Primary LCD
Secondary LCD
1
9
3
2
7
4
6
5
10
8
11 13 14 15
Rear Panel
16
POWER
12VDC
INPUT TEMP
RS232
PROBE
12
ALT FunctionsFunctions
RCL
LOG
ALT
SET
LOCK/CLR
ATC
TC
MODE
RANGE
GLP
CFM
CAL
pH/mV & EC/TDS/NaCl
HI 255 Combined Meter
TC Factor
TC
ATC Select Temperature
Compensation
Recall Log Data
RCL
SET Set Parameters
Select Measure Mode
MODE
Confirm/GLP Data
CFM/GLP
Calibration
CAL
Change Parameter Value
Store Log Data
LOG
Lock Current Range
Clear Calibration
LOCK/CLR
Select Measure Unit
Scroll Log Data
RANGE
REF
/
BUFFER pH
INTVDATETIME%
ppm
S
3
2
1
BUF
WRONG
READY
CFM
NaCl
pHmVg / lLOGCAL

5
HI 255
SPECIFICATIONS
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6
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HI 255
SPECIFICATIONS (cont.)

7
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.

8
The pH is displayed on the primary LCD and the temperature on the
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.
4cm
(1 )
1/2”
pH
pH

9
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.
mV
mV
mV

10
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.
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.
ALT
ATC