Hanna Instruments HI 250 User manual

1
Instruction Manual
HI 250 HI 251
Microprocessor-Based
pH/mV/ºC
Bench Meters
www.hannainst.com

2
TABLE OF CONTENTS
WARRANTY ................................................................................................................... 2
PRELIMINARY EXAMINATION ........................................................................................... 3
GENERAL DESCRIPTION.................................................................................................... 3
FUNCTIONAL DESCRIPTION ............................................................................................. 4
HI 250 SPECIFICATIONS .................................................................................................. 5
HI251SPECIFICATIONS ...................................................................................................6
OPERATIONAL GUIDE ....................................................................................................... 7
pHCALIBRATION................................................................................................................10
GOOD LABORATORY PRACTICE (GLP).............................................................................13
LOGGINGFUNCTION.......................................................................................................15
SETUP.......................................................................................................................18
TEMPERATURE CALIBRATION (for technical personnel only)............................................ 22
mV CALIBRATION (for technical personnel only)............................................................... 23
RELATIVE mV CALIBRATION.......................................................................................... 24
PC INTERFACE ............................................................................................................... 25
pH VALUES AT DIFFERENT TEMPERATURES .................................................................... 27
ELECTRODE CONDITIONING & MAINTENANCE .............................................................. 28
TROUBLESHOOTING GUIDE .......................................................................................... 31
TEMPERATURE CORRELATION FOR pH SENSITIVE GLASS ............................................... 32
ACCESSORIES......................................................................................................................33
WARRANTY
HI 250 and HI 251 are guaranteed for two years against defects in workmanship
and materials when used for their 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
instruments. 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 instruments
are 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.
Dear Customer,
Thank you for choosing a Hanna Instruments product.
Please read this instruction manual carefully before using the instruments.
This manual will provide you with the necessary information for correct use of
the instruments, as well as a precise idea of their 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.
These instruments are in compliance with directives.

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 7669/2W Temperature Probe
 HI 76404 Electrode Holder
 pH 4.01 & 7.01 Buffer Solutions (20mL 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 250 and HI 251 are logging microprocessor-based pH and
temperature bench meters.
HI 251 can also measure Oxidation-Reduction Potential (ORP) in mV range.
Relative mV feature is also provided.
pH measurements are compensated for temperature effect manually or
automatically with the HI 7669/2W temperature probe.
One, two or three-point calibration is possible, using five memorized buffers
(4.01, 6.86, 7.01, 9.18 and 10.01 pH).
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 the last pH calibration.
The instruments can store data in memory at the users request for later
retrieval.
Hanna Instruments reserves the right to modify the design, construction
and appearance of its products without advance notice.
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) /ºC key, to manually decrease temperature value or other parameters.
5) /ºC key, to manually increase temperature value or other parameters.
6) RCL key, to enter/exit recall mode.
7) LOG key, to store measured data.
8) SET/CLR key, to enter/exit setup mode, clear pH calibration or delete
logged data.
9) RANGE key, to select measurement range (HI 251 only) or to switch
focused data.
10) ON/OFF switch.
11) Power supply socket.
12) BNC electrode connector.
13) Electrode reference socket.
14) Temperature probe socket.
15) RS232 serial communication connector.
FUNCTIONAL DESCRIPTION
Front Panel
Primary LCD
Secondary LCD
1
9
3
2
7
4
6
5
10
8
POWER
12VDC
INPUT
REF
TEMP
11 12 13 14
Rear Panel
C
CAL
CFM
READY
1
2
3
BUF
WRONG
LOG mV pH TIME% DATE INTV
BUFFER pH
RS232
15
Functions pH Calibration - 3 points
RCL LOG
CLR
SET
CC
RANGE
GLP
CFM
CAL
pH / ORP Meter
HI 251
Confirm Calibration
in selected pH Buffer
CFM
Select pH Buffer
/
Start/Exit Calibration
CAL
Select pH/ORP/ mV
Scroll Log Data Rel
RANGE
GLP Show GLP Data
LOG Store Log Data
SET/CLR Set Instrument Parameters
Clear Calibration/Log Data
RCL Recall Log Data

5
HI 250
SPECIFICATIONS
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6
HI 251
SPECIFICATIONS
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7
OPERATIONAL GUIDE
POWER CONNECTION
Plug the 12 VDC adapter into the power supply socket.
Note: These instruments use non volatile memory to retain the pH, mV,
temperature calibrations 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.
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.
pH MEASUREMENTS
Make sure the instruments have been calibrated before
taking pH measurements.
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
secondary LCD.
If the reading is out of range, the closest full-scale value will be displayed
blinking on the primary LCD.
pH
C
C
CAL
CFM
READY
1
2
3
BUF
WRONG
LOG mV pH TIME% DATE INTV
BUFFER pH
pH
C

8
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 7669/2W 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, simple 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 9.9 ºC to 120.0 ºC).
mV/ORP MEASUREMENTS (HI 251 only)
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.
If the reading is out of range, the closest full-scale value will be displayed
blinking on the primary LCD.
C
C C
mV
C
mV
C

9
RELATIVE mV MEASUREMENTS (HI 251 only)
Press RANGE until rEL message will be displayed on the secondary LCD
line for about one second and mV tag will blink. After one second the
temperature will be displayed on the secondary LCD.
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.
TEMPERATURE MEASUREMENTS
Connect the HI 7669/2W temperature probe to the appropriate
socket and turn the instrument on.
Immerse the temperature probe into the sample and allow
the reading on the secondary LCD to stabilize.
mV
C

10
pH CALIBRATION
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 30).
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 7.01 or 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
instruments also allow one-point calibration, as described on page 12.
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 
1
BUF
 tags will appear
and the 7.01 buffer will be displayed on the
secondary LCD.
If necessary, press the ARROW keys to select a different buffer value.
CAL
1
BUFFER pH
BUF
pH