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

11
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 second expected buffer value on the secondary
LCD.
Note: The instruments 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, the
READY tag will be displayed and the 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 instruments will automatically skip the buffers used for the first and
second calibration points.
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, the
READY tag will be displayed and the CFM tag will blink.
Press CFM to confirm calibration.
The instruments store the calibration values and return
to normal measurement mode.
CAL
2
BUF
pH
BUFFER pH

12
Note: If the value measured by the instruments is not close to the
selected buffer, WRONG 
BUF
 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 Proce-
dure (see page 30). If necessary, change the buffer or the
electrode.
If WRONG, Buffer pH tags and Old tag on the secondary LCD
are displayed blinking, an inconsistency between new and previous
(old) calibration is detected. Clear calibration parameters by
pressing SET/CLR and proceed with calibration from the current
calibration point (the instruments will keep all confirmed values
during current calibration).
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 instrumentswill 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 instrumentswill 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 SET/CLR before exiting calibration.

13
GOOD LABORATORY PRACTICE (GLP)
GLP is a set of functions that allows storage and retrieval of data regarding the
maintenance and status of the electrode.
All data regarding last calibration (one, two or three-point) is stored for the
user to review when necessary. This data includes the following: calibration
time stamp, offset (mV), slope (%), calibration buffers and the time until a
new calibration is required.
CALIBRATION ALARM TIME-OUT
HI 250 and HI 251 allow the user to set the number of days before the next
required pH calibration. This value can be set from 1 to 7 days. The default
setting is OFF (disabled).
The instruments check if the time-out time has expired. If the time elapsed, the
CAL INTV tags will blink as a reminder.
Note: If the instruments were not calibrated, the CAL INTV tags will be
displayed even if the feature is disabled in SETUP menu.
LAST CALIBRATION DATA
The last calibration data is stored automatically after a successful calibration.
To view the pH calibration data, press GLP while in normal measurement mode.
The instruments will display the time (hh:mm) of the last calibration.
Press the ARROW keys to view the next logged calibration parameter
(pressing the ºC key):
The date (yyyy.mm.dd).
The pH calibration offset.
The pH calibration slope (the GLP slope is the average of the calibration
slopes; the percentage is referred to the ideal value of 59.16 mV/pH).
TIME
CAL
DATE
CAL
CAL mV
%
CAL

14
The calibration buffers in calibrating order.
The first pH calibration buffer:
The second pH calibration buffer:
The third pH calibration buffer:
Note: The OLd message displayed beside the pH value means that
this buffer was not used during last calibration. Press and hold
down SET/CLR if you want to see calibration date (or time if old
calibration was made in the same day with current calibration).
If no bUF message appears on the LCD, the instruments inform
you that calibration was performed in less than three points.
pH resolution during calibration.
Calibration Alarm Time-Out status:
if disabled.
or the number of days until the calibration alarm will be displayed.
or if expired (7 days ago).
CAL pH
BUF
CAL pH
BUF
CAL
BUF
CAL INTV
CAL
CAL pH
BUF

15
LOGGING FUNCTION
Up to 50 LOG samples can be stored into memory.
LOGGING THE CURRENT DATA
To store the current reading into memory press LOG while the instruments are
in measurement mode.
The instruments will display the current date (mm.dd) on the primary LCD,
the record number on the secondary LCD and LOG tag will blink for a few
seconds (see example below: record No. 5 dated September 14):
If there are less than 6 memory locations remaining, the record number and
Lo message will blink to alert the user.
If the log space is full, FULL LOC message will be displayed and no more
data will be saved.
When LOG is pressed, a complete set of information is stored: date, time, pH,
mV, temperature and calibration data.
CAL
LOG
LOG
LOG
The instrument ID.
Note:  Press GLP at any moment and the instruments will return to
measurement mode.
If calibration has not been performed, the instruments display
no CAL message blinking.

16
VIEW LOGGED DATA
Press RCL while in measurement mode to retrive the stored information.
If no data were logged, the instruments display:
Otherwise, the instruments will display the pH or relative mV value (HI 251
only) on the primary LCD and the last stored record number on the secondary
LCD, along with LOG tag.
or
Pressing the ARROW keys, the instruments will display the same parameter
but for a different record.
Press RANGE and the instruments will display the next logged parameter as
follows:
The mV value on the primary LCD and the record number on the secondary
LCD (HI 251 only).
The temperature value on the primary LCD and the record number on
the secondary LCD.
Note: When the pH, mV or temperature is displayed, if SET/CLR is pressed
and hold down, the secondary LCD will display the record date.
 The time on the primary LCD, along with TIME tag.
LOG
LOG pH
LOG pH
LOG mV
LOG
C
LOG TIME
mVLOG

17
LOG DATE
LOG mV
 The date on the primary LCD, along with DATE tag.
The calibration offset on the primary LCD and OFS message on the
secondary LCD.
The calibration slope on the primary LCD and SLP message on the
secondary LCD.
Note: If in Relative mV RECALL mode, the instruments will display ----
message on the primary LCD (HI 251 only).
When the time, date, year, offset or slope is displayed, if SET/CLR
is pressed and hold down, the secondary LCD will display the record
number.
The dEL message on the primary LCD and the selected record on the
secondary LCD, along with LOGtag.
Note: If one of the ARROW keys is pressed while dEL and record
number is displayed, the next/previous record number is selected.
If LOG is pressed, the secondary LCD will display ALL message.
Pressing LOG again, the secondary LCD will display the record
number.
Press SET/CLR to delete the selected or all records.
If del ALL option was selected, all records are deleted and the
instrument returnsto measurement mode.
Note:After LOG is pressed while in measurement mode or a selected record is
deleted, the instrument will display the amount of free log space for about
one second (e.g. 25 records free).
Press RCL to leave RECALL mode at any time.
LOG
%
LOG
LOG
LOG

18
SETUP
Setup mode allows viewing and modifying the following parameters:
Current Time
Current Date
pH Resolution
Beep Status
Baud Rate (serial communication)
Command prefix (serial communication)
Calibration Alarm Time-Out
Instrument ID
To enter SETUP mode press SET while the instruments are in measurement mode.
Select a parameter with the ARROW keys.
Press CAL if you want to change a parameter value. The selected parameter
will start blinking.
Press RANGE to toggle between displayed parameters.
Press the ARROW keys to increase or decrease the displayed value.
Press CFM to save the modified value or CAL to escape.
Press the ARROW keys to select the next/previous parameter.
CURRENT TIME SET
Press CAL when the current time is displayed. The hour will start blinking.
Press the ARROW keys to change the hour.
Press RANGE. The minutes will start blinking.
Press the ARROW keys to change the minutes.
Press CFM to save the modified value.
Press CAL to escape without saving.
TIME
TIME

19
CURRENT DATE SET
Press CAL when the current date is displayed. The year will start blinking.
Press the ARROW keys to change the year.
Press RANGE. The month will start blinking.
Press the ARROW keys to change the month.
Press RANGE. The day will start blinking.
Press the ARROW keys to change the day.
Press CFM to save the modified value.
Press CAL to escape without saving.
pH RESOLUTION SET
Press CAL when the pH range is displayed. The pH range (0.01 or 0.1) will
start blinking.
Press the ARROW keys to change the pH range.
Press CFM to save the modified pH range.
Press CAL to escape without saving.
BEEP STATUS SET
Press CAL when the beep status is displayed. Beep status (On or OFF) will
start blinking.
DATE
DATE
DATE
pH

20
Press the ARROW keys to change the beep status (On or OFF).
Press CFM to save the modified beep status.
Press CAL to escape without saving.
BAUD RATE SET
Press CAL when the baud rate is displayed. The baud rate (600, 1200, 2400,
4800 or 9600) will start blinking.
Press the ARROW keys to change the baud rate value.
Press CFM to save the modified baud rate value.
Press CAL to escape without saving.
SERIAL COMMUNICATION COMMAND PREFIX SET
Press CAL when the command prefix is displayed. The command prefix (0 to
47) will start blinking.
Press the ARROW keys to change the command prefix.
Press CFM to save the modified command prefix value.
Press CAL to escape without saving.
Note:  See the PC interface section on page 25 for a complete explanation.
 The command prefix must be 16 if HI 92000 PC software is used.
CALIBRATION ALARM TIME-OUT SET
Press CAL when the calibration time-out is displayed. Calibration time-out
(OFF or 1 to 7 days) will start blinking.
Press the ARROW keys to change the calibration time-out value.
Press CFM to save the modified calibration time-out value.
Press CAL to escape without saving.
CAL INTV