Hanna Instruments HI 2550 User manual

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Multiparameter
pH/ORP/°C
EC/TDS/NaCl
Bench Meter
HI2550
Instruction Manual
www.hannainst.com

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Dear Customer,
Thank you for choosing a Hanna Instruments product.
Please read this instruction manual carefully before using this instrument.
This manual will provide you with the necessary information for correct
use of this 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 view our worldwide contact list at
www.hannainst.com.
All rights are reserved. Reproduction in whole or in part is prohibited
without the written consent of the copyright owner.

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PRELIMINARY EXAMINATION ..........................................................4
GENERAL DESCRIPTION..................................................................4
FUNCTIONAL DESCRIPTION.............................................................5
SPECIFICATIONS............................................................................6
OPERATIONAL GUIDE.....................................................................8
AUTO‑RANGING...........................................................................12
pH CALIBRATION .........................................................................13
pH BUFFER TEMPERATURE DEPENDENCE ......................................18
RELATIVE mV CALIBRATION..........................................................19
EC/TDS CALIBRATION...................................................................19
CONDUCTIVITY VERSUS TEMPERATURE CHART...............................21
NaCl CALIBRATION.......................................................................22
GOOD LABORATORY PRACTICE (GLP)..............................................23
LOGGING FUNCTION.....................................................................28
SETUP........................................................................................35
TEMPERATURE CALIBRATION (FOR TECHNICAL PERSONNEL ONLY)42
mV CALIBRATION (FOR TECHNICAL PERSONNEL ONLY) ...................44
PC INTERFACE .............................................................................45
ELECTRODE CONDITIONING AND MAINTENANCE.............................51
TROUBLESHOOTING GUIDE ..........................................................54
TEMPERATURE CORRELATION FOR pH SENSITIVE GLASS.................55
ACCESSORIES..............................................................................56
TABLE OF CONTENTS

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GENERAL DESCRIPTION
The HI2550 is a microprocessor based pH, ORP, Conductivity (EC), TDS,
NaCl, and Temperature Bench Meter. Relative mV feature is also provided.
pH measurements are compensated for temperature effect manually or
automatically with the HI7662 temperature probe.
Up to a five‑point pH calibration can be performed using seven standard
buffers and two custom buffers.
A calibration due alarm can be set to alert the user that too much time
has elapsed since the last pH calibration.
Conductivity and TDS features auto‑ranging, which automatically selects
the scale with the highest resolution. Conductivity measurements are
compensated for temperature manually or automatically with a tem‑
perature sensor located inside the probe. The temperature coefficient is
user selectable. Temperature compensation can be disabled to measure
actual conductivity.
The GLP feature provides data consistency.
Data can be stored in the meters memory for later retrieval. The meters
memory can hold 200 manually logged points and 500 lot logging points.
An USB connection ensures communication with a PC.
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, please contact your local Hanna Instruments Office.
Each instrument is supplied with:
• HI1131B Glass‑body Combination pH Electrode with 1 m (3.3’)
Cable
• HI76310 Conductivity / TDS probe
• HI7662 Temperature Probe
• HI76404N Electrode Holder
• pH4.01 & 7.01 Buffer Solutions (20 mL each)
• HI7082 Electrolyte Solution
• 12VDC Power Adapter
• Instruction Manual
• Quick Reference Guide
• Quality Certificate
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.
PRELIMINARY EXAMINATION

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1) Liquid Crystal Display (LCD).
2) CAL key, to enter and exit calibration mode.
RCL key (alternate function), to enter and exit memory recall.
3) CFM/GLP key, to confirm calibration selection, different setup values or to
display Good Laboratory Practice information.
4) ºC key, to manually increase temperature value or other parameters.
TC key (alternate function), to view temperature coefficient value.
5) ºC key, to manually decrease temperature value or other parameters.
ATC key (alternate function), to select EC temperature compensation mode.
6) SETUP key, to enter/exit SETUP mode.
LOCK key (alternate function), to freeze current EC range on the LCD.
7) RANGE key, to select measurement range (pH, mV, EC), switch to focused
data in SETUP or toggle between buffer value and temperature during
calibration.
MODE key (alternate function) to select mV or Rel mV on mV range or EC,
TDS, NaCl on EC range.
8) LOG/CLR key, to store a value into memory, to clear pH calibration, or to
select to delete log records or lots.
9) ALT key, to select alternate function.
10) ON/OFF switch.
11) Power supply socket.
12) USB connector.
13) EC electrode connector.
14) BNC electrode connector.
15) Temperature probe socket.
16) Electrode reference socket.
FUNCTIONAL DESCRIPTION
Front Panel
Rear Panel

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SPECIFICATIONS
(*)Uncompensated conductivity (or TDS) is the conductivity (or TDS) value without
temperature compensation.
RANGE
–2.0 to 16.0 pH
–2.00 to 16.00 pH
–2.000 to 16.000 pH
±999.9 mV (ISE & ORP)
±2000 mV (ISE & ORP)
0.00 to 29.99 µS/cm
30.0 to 299.9 µS/cm
300 to 2999 µS/cm
3.00 to 29.99 mS/cm
30.0 to 200.0 mS/cm
up to 500.0 mS/cm uncompensated(*) conductivity
0.00 to 14.99 ppm
15.0 to 149.9 ppm
150 to 1499 ppm
1.50 to 14.99 g/l
15.0 to 100.0 g/l
up to 400.0 g/l uncompensated(*) TDS
(with 0.80 factor)
0.0 to 400.0% NaCl
–20.0 to 120.0 ºC (pH, EC range)
RESOLUTION
0.1 pH
0.01 pH
0.001 pH
0.1 mV (±1000 mV)
1 mV (±2000 mV)
0.01 µS/cm
0.1 µS/cm
1 µS/cm
0.01 mS/cm
0.1 mS/cm
0.01 ppm
0.1 ppm
1 ppm
0.01 g/l
0.1 g/l
0.1% NaCl
0.1 ºC

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ACCURACY
@ 20 °C / 68 °F
±0.01 pH
±0.002 pH
±0.2 mV (±999.9 mV)
±1 mV (±2000 mV)
±1 % reading (±0.05 µS/cm or 1 digit,
whichever is greater)
±1 % of reading (±0.03 ppm or 1 digit,
whichever is greater)
±1% of reading
±0.4 ºC (excluding probe error)
Rel mV offset range ±2000 mV
pH Calibration 1, 2, 3, 4 or 5 point calibration,
7 standard buffers available
EC Calibration
1 point slope calibration;
6 buffers available:
84.0, 1413 µS/cm
5.00, 12.88, 80.0, 111.8 mS/cm
1 point offset: 0.00 µS/cm
NaCl Calibration 1 point with HI7037L buffer (optional)
Temperature
compensation
Manual or Automatic from:
–20.0 to 120.0 ºC (pH RANGE)
–20.0 to 120.0 ºC (EC RANGE)
(can be disabled on conductivity range to measure
actual conductivity
Conductivity
temperature
coefficient
0.00 to 6.00 %/ºC
(for EC and TDS only)
default value is 1.90 %/ºC
TDS factor 0.40 to 0.80 (default value is 0.50)
pH Electrode HI1131B
EC Probe HI76310
Temperature probe HI7662
Input impedance
(BNC input) 1012 ohms
Log on demand feature 200 records
Log Interval feature
500 records Stability logging (”StAb”),
5, 10, 30 sec
1, 2, 5, 10, 15, 30, 60, 120, 180 min
PC communication Optoisolated USB
Power supply 12 VDC adapter
Dimensions 235 x 222 x 109 mm (9.2 x 8.7 x 4.3”)
Weight 1.3 Kg (2.9 lb); kit with holder 2.1 Kg (4.6 lb)
Environment 0 – 50 ºC (32 – 122 ºF)
max. 95% RH non‑condensing
Warranty 2 years

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OPERATIONAL GUIDE
POWER CONNECTION
Plug the 12 VDC adapter into the power supply socket.
Notes: This instrument uses non volatile memory to retain the
calibration parameters and all other settings, even when unplugged.
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 located on
the rear panel.
• All LCD tags are displayed and a beep is sounded while the instruments
perform a self test.
• The instrument will display “LoAd” message and “ ” blinking until
initialization is complete.
Notes: The instrument starts in the same range and mode as it
was at power off.
The ALT&MODE keys change the measuring modes:
- mV or Rel mV
- EC or TDS or NaCl
The RANGE key toggles between measurement ranges:
- pH, mV or Rel mV, EC or TDS or NaCl.
pH MEASUREMENTS
Make sure the instrument has been calibrated before
taking pH measurements.
• Submerse the electrode tip and the temperature
probe approximately 3 cm (1¼”) into the
sample to be tested and stir gently. Allow time
for the electrode to stabilize.

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• 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 submerse
the HI7662 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 temperature compen‑
sation can be used by disconnecting the temperature probe.
The display will show the last temperature reading the
“MTC” tag and the “ºC” tag blinking.
The temperature can now be adjusted with the ARROW
keys (from –20.0 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.
The surface of the ORP electrode must be clean and smooth in order to
obtain an accurate measurement.
• Press RANGE to enter mV range.
• Submerse the tip of the ORP electrode 3 cm (1¼”)
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.

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• 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
“mV” and “Rel” tags are displayed.
The reading displayed by the instrument is equal to the difference between
the current mV input value and the relative mV offset established in the
relative mV calibration.
CONDUCTIVITY MEASUREMENTS
Connect the conductivity probe to the instrument.
• Press the RANGE key to enter conductivity measurement range (EC).
• Submerse the probe into the solution to be tested. The
sleeve holes must be completely submersed. 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.
• 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 key was pressed and the reading goes out of range, the
full‑scale value of the frozen range will be displayed blinking.
The conductivity reading is affected by temperature.
Three options for temperature compensation are available in conductivity
measurement mode.

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Automatic (ATC): The conductivity probe has a built‑in temperature
sensor; the temperature value is used to automatically compensate the
EC/TDS reading. The “ATC” tag is displayed when this option is active.
Manual (MTC): The temperature value, shown on the secondary LCD,
can be manually set with the ARROW keys. The “ºC” tag blinks and
the “MTC” tag is displayed when this option is active. This value will be
used to compensate the EC/TDS reading.
No Compensation (notc): The temperature value is displayed, but not
taken into account. When this option is selected the “ºC” tag will blink
with slower frequency and the “NO TC” tag is displayed. The reading
displayed on the primary LCD is the uncompen‑
sated 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 is detected, ATC mode can not be selected and the instrument
displays “‑‑‑‑” on the secondary LCD.
If temperature compensation is selected, measurements are compensated
using the temperature coefficient (default value 1.90 %/ºC). To change
the temperature coefficient, enter the setup mode and select “tc” (see
SETUP for details, page 36). The current temperature coefficient can
be quickly viewed by pressing the ALT&TC keys. The value is briefly
displayed on the LCD.
• If the temperature reading exceeds the limits of the meter (–20.0 ºC
to 120.0 ºC), the “ºC” tag will blink and the closest full scale value
will be displayed.
TDS MEASUREMENTS
Press the ALT&MODE keys while in EC range. The instrument will switch
to TDS measuring range. The 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 g/L for MTC/
ATC mode or 400.0 g/L for uncompensated TDS) will be displayed
blinking.
• If LOCK was pressed and the reading goes out of range, the full‑scale
value of the frozen range will be displayed blinking.

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AUTO-RANGING
The EC and TDS scales are auto‑ranging. The meter automatically sets
the scale with the highest possible resolution.
By pressing ALT&LOCK, the auto‑ranging feature is disabled and the
current range is frozen on the LCD. The “LOCK“ tag will be displayed
on the LCD.
Note: Auto-ranging 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.
When auto‑ranging is disabled and the reading goes 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
In pH and ORP mode, connect the HI7662 temperature probe to the
appropriate socket.
Submerse the temperature probe into the sample and allow the reading
on the secondary LCD to stabilize.
In EC/TDS/NaCl range, the HI76310 probe has a built‑in temperature
sensor.

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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 day.
• 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 53).
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 pH7.01 or 6.86 as first buffer
and pH4.01 as second buffer. If you are measuring in the alkaline range,
use pH7.01 or 6.86 as first buffer and pH10.01 or 9.18 as second buffer.
PROCEDURE
Calibration can be performed at up to five‑points.
For accurate measurements, a three-point calibration is recommended.
The calibration buffer can be selected from the calibration buffer list
that includes the custom buffers and the memorized standard buffers:
• pH1.68, 4.01, 6.86, 7.01, 9.18, 10.01 and 12.45
The custom buffers allow the user to calibrate in a buffer solution different
from a standard one. Up to two custom buffers can be set in SETUP menu
(see page 36). Each custom buffer value can be changed in a ±1.0 pH
window around the set value, during calibration, when it is selected; the
“Cust.” tag will be displayed.
The instruments will automatically skip the buffer used during calibration
and the buffers which are in a ±0.2 pH window, around one of the
calibrated buffers.
All new calibrations will override existing stored calibration data in
a ±0.2 pH window. The slopes adjacent to the new points will be
reevaluated.

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FIVE-POINT CALIBRATION
• Submerse the pH electrode and the temperature
probe approximately 3 cm (1¼”) into a buffer
solution and stir gently. The temperature probe
should be close to the pH electrode.
• Press CAL. The “CAL” and “ ” tags will appear
and the “7.01” buffer will be displayed on the
secondary LCD. The temperature compensation
mode tag is displayed also.
• 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 “CFM” tag will blink.
•Press CFM to confirm calibration.
•The calibrated value is then displayed on the primary
LCD and the second expected buffer value on the
secondary LCD.
• After the first calibration point is confirmed, submerse the pH electrode
and the temperature probe approximately 3 cm (1¼”) 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 “CFM” tag will blink.
•Press CFM to confirm calibration.
•The calibrated value is then displayed on the
primary LCD and the third expected buffer value on
the secondary LCD.
• After the second calibration point is confirmed, submerse the pH
electrode and the temperature probe approximately 3 cm (1¼”)
into the third buffer solution and stir gently. The temperature probe
should be close to the pH electrode.

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FOUR, THREE OR TWO-POINT CALIBRATION
• Proceed as described in “FIVE‑POINT CALIBRATION” section.
• Press CAL after the fourth, third or second calibration point was
confirmed. The instruments will memorize the calibration data and
return to measurement mode.
• 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 “CFM” tag will blink.
•Press CFM to confirm calibration.
•The calibrated value is then displayed on the primary
LCD and the fourth expected buffer value on the
secondary LCD.
• After the third calibration point is confirmed, submerse the pH
electrode and the temperature probe approximately 3 cm (1¼”)
into the fourth 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 “CFM” tag will blink.
•Press CFM to confirm calibration.
•The calibrated value is then displayed on the primary
LCD and the fifth expected buffer value on the second‑
ary LCD.
• After the fourth calibration point is confirmed, submerse the pH
electrode and the temperature probe approximately 3 cm (1¼”)
into the fifth 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 “CFM” tag will blink.
•Press CFM to confirm the fifth calibration point.
• The instrument stores the calibration value and returns
to normal measurement mode.

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ONE-POINT CALIBRATION
Two SETUP selectable options are available: “Pnt” and “OFFS”.
If the “Pnt” option is selected, the new calibration point overrides an
existing one. The adjacent slopes will be reevaluated.
If the “OFFS” option is selected, an electrode offset correction is
performed.
The adjacent slopes will remain unchanged.
• Proceed as described in “FOUR, THREE or TWO‑POINT CALIBRATION”
section.
• Press CAL after the first calibration point was confirmed. The instru‑
ments will memorize the one‑point calibration data and return to
measurement mode.
Notes: • If the value measured by the instrument is not close to
the selected buffer, “WRONG” “ ” and “WRONG” “ ” tags will
blink alternately. Check if the correct buffer has been used, or clean
the electrode by following the Cleaning Procedure (see page 53). If
necessary, change the buffer or the electrode.
• When a custom buffer is displayed, the “Cust.” tag is
displayed. To change the custom buffer value in accordance with the
buffer temperature proceed as described in “WORKING WITH CUSTOM
BUFFERS” (see page 17).
• If the buffer temperature or the manual temperature
exceeds the temperature limits of the buffer, “WRONG” tag and
temperature reading will blink.
• If “WRONG”, “Buff.” tags and “OLd” message are
displayed blinking on the secondary LCD line, an inconsistency be‑
tween new and previous (old) calibration is detected. Clear calibration
parameters and proceed with calibration from the current calibration
point. The instrument will keep all confirmed values during current
calibration.
• To clear calibration parameters for all uncalibrated buffers
starting with current buffer, press CLR. The calibration will continue
from the current point. If this procedure is performed while calibrating
in the first calibration point, the instrument returns to measurement
mode.
• Press RANGE to toggle between pH
buffer, calibration buffer number and temperature
reading.

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• Each time a buffer is confirmed, the new calibration data replaces the
old calibration data for the corresponding buffer. If current buffer has
no previous data stored and the calibration is not full (five buffers),
the current buffer is added to the existing calibration. If the existing
calibration is full, the instrument asks which buffer to replace.
Press the ARROW keys to select another buffer to be replaced.
Press CFM to confirm the buffer that will be replaced.
Press CAL to leave calibration without replacing.
Note: If the replaced buffer is outside the ±0.2 pH window, around
each of the calibrated buffers, it is possible to select this buffer for
next calibration during current calibration.
WORKING WITH CUSTOM BUFFERS
If a custom buffer was set in SETUP menu, it can be selected during cali‑
bration by pressing the ARROW keys. The “Cust.” tag will be displayed.
Press SETUP if you want to adjust the buffer value. The buffer value
will start blinking.
Use the ARROW keys to change the buffer value.
After 5 seconds, the buffer value is updated. Press SETUP if you want
to change it again.
Note: Custom buffer value can be adjusted in a ±1.00 pH window,
around the set value.

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The temperature has an effect on pH. The calibration buffer solutions are
affected by temperature changes to a lesser degree than normal solutions.
During calibration the instrument will automatically calibrate to the pH
value corresponding to the measured or set temperature.
During calibration the instrument will display the pH buffer value at 25 ºC.
pH BUFFER TEMPERATURE
DEPENDENCE
TEMP pH BUFFERS
°C °F 1.68 4.01 6.86 7.01 9.18 10.01 12.45
0 32 1.67 4.01 6.98 7.13 9.46 10.32 13.38
5 41 1.67 4.00 6.95 7.10 9.39 10.24 13.18
10 50 1.67 4.00 6.92 7.07 9.33 10.18 12.99
15 59 1.67 4.00 6.90 7.05 9.27 10.12 12.80
20 68 1.68 4.00 6.88 7.03 9.22 10.06 12.62
25 77 1.68 4.01 6.86 7.01 9.18 10.01 12.45
30 86 1.68 4.02 6.85 7.00 9.14 9.96 12.29
35 95 1.69 4.03 6.84 6.99 9.11 9.92 12.13
40 104 1.69 4.04 6.84 6.98 9.07 9.88 11.98
45 113 1.70 4.05 6.83 6.98 9.04 9.85 11.83
50 122 1.71 4.06 6.83 6.98 9.01 9.82 11.70
55 131 1.72 4.08 6.84 6.98 8.99 9.79 11.57
60 140 1.72 4.09 6.84 6.98 8.97 9.77 11.44
65 149 1.73 4.11 6.84 6.99 8.95 9.76 11.32
70 158 1.74 4.12 6.85 6.99 8.93 9.75 11.21
75 167 1.76 4.14 6.86 7.00 8.91 9.74 11.10
80 176 1.77 4.16 6.87 7.01 8.89 9.74 11.00
85 185 1.78 4.17 6.87 7.02 8.87 9.74 10.91
90 194 1.79 4.19 6.88 7.03 8.85 9.75 10.82
95 203 1.81 4.20 6.89 7.04 8.83 9.76 10.73

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RELATIVE mV CALIBRATION
• Press CAL when the instrument is in RELATIVE mV measurement
mode. The “mV Rel” and “ ” tags will be displayed. Absolute mV
is displayed on the primary LCD and “AbS” message is displayed
on the secondary LCD.
• When the absolute reading is stable and in measurement range, the
instrument asks for confirmation.
• If the reading is out of range, “WRONG” tag will be displayed.
• Press CFM to confirm the absolute value. The instrument will display
0.0 mV on the primary LCD and “rEL” message on the secondary
LCD. In this moment the relative mV offset is equal to absolute mV
reading.
• Use the ARROW keys if you want to change the displayed relative
mV value.
• Press CFM to confirm the relative mV value. The instrument returns
to measurement mode.
Note: The relative mV value can be changed only inside the relative
mV offset window (± 2000 mV).
EC/TDS CALIBRATION
Selectable calibration points for conductivity 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. Submerse the probe into the solution. The sleeve
holes must be completely submersed. 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.
The “BUF” and “CAL” tags are displayed. The primary
LCD will display the EC reading. The secondary LCD will
display the value of the standard. The temperature
compensation mode tag is also displayed. The “ ” and
“~” tags will blink.
Note: The 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 at 0.00 µS. The slope is
evaluated when the calibration is performed at any other point.

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Select the desired value with the ARROW keys, if necessary.
When the reading is stable, “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.
Notes: • If the 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 calibration solution has been used or clean
the probe by following the Cleaning Procedure (see page 53).
• If the meter is in ATC or MTC mode and the buffer
temperature is out of the 0.0 °C to 60.0 ºC interval, “WRONG”
“ºC” tags and the temperature will blink.
• 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 “CELL” (see SETUP for details, page 36).