Hanna Instruments HI88713-01 User manual

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www.hannainst.com
HI88713
ISO Turbidity Meter
Instruction Manual

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TABLE OF CONTENTS
Dear Customer,
Thank you for choosing a Hanna Instruments product. This manual will provide you with the necessary
information for correct use of the instrument.
Please read this instruction manual carefully before using the instrument.
If you need additional technical information, do not hesitate to e‑mail us at [email protected] or
see the back side of this manual for our worldwide sales and technical service contacts.
This instrument is in compliance with directives.
PRELIMINARY EXAMINATION .....................................................................................................................3
GENERAL DESCRIPTION.............................................................................................................................3
ABBREVIATIONS.......................................................................................................................................4
PRINCIPLE OF OPERATION.........................................................................................................................4
FUNCTIONAL DESCRIPTION........................................................................................................................6
SPECIFICATIONS.......................................................................................................................................8
GENERAL TIPS FOR AN ACCURATE MEASUREMENT.......................................................................................9
START UP...............................................................................................................................................15
RANGE SELECTION..................................................................................................................................16
TUTORIAL MODE.....................................................................................................................................16
HELP MODE ...........................................................................................................................................17
MEASUREMENT PROCEDURE ..................................................................................................................17
CALIBRATION PROCEDURE ......................................................................................................................20
GOOD LABORATORY PRACTICE (GLP).........................................................................................................26
RESTORE FACTORY CALIBRATION .............................................................................................................26
LOG & LOG RECALL..................................................................................................................................27
SETUP ..................................................................................................................................................28
PC INTERFACE ........................................................................................................................................30
ACCESSORIES.........................................................................................................................................31
WARRANTY ............................................................................................................................................31
RECOMMENDATIONS FOR USERS.............................................................................................................31

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Please examine this Product carefully. Make sure the instrument is not damaged. If any damage has
occurred during the shipment, please contact your local Hanna Instruments Office.
This HI88713 Turbidity bench meter is supplied complete with:
• Six Sample Cuvettes and Caps
• Calibration Cuvettes
• Silicone Oil
• Cloth for wiping the cuvettes
• AC/DC power adapter
• Instruction Manual
• Instrument Quality Certificate
Note:Save all packing material until you are sure that the instrument works correctly. Any defective
item must be returned in the original packing with the supplied accessories.
PRELIMINARY EXAMINATION
The HI88713 Turbidity bench meter is a high accuracy, meter that benefits from Hanna Instruments’
years of experience as manufacturer of analytical instruments.
The HI88713 Turbidity bench meter meets and exceeds the requirements of ISO 7027 standard.
The instrument is based on a state‑of‑the‑art optical system which guarantees accurate results, assures
long term stability and minimizes stray light and color interferences. It also compensates for variations
in intensity of the LED, making no need for frequent calibration.
The 25 mm round cuvettes made from special optical glass guaranties reproductibility and consistency
of the measurements.
Turbidity measurements can be made in four modes: FNU (Formazin Nephelometric Units) ratio
mode FAU (Formazin Attenuation Units) NTU (Nephelometric Turbidity Units) NTU non‑ratio mode.
Alternative EBC (European Brewery Comitee) measuring units are available wen measuring in NTU modes.
Normal measurement, continuous measurement or signal averaging measurement can be selected,
depending on the sample and desired accuracy.
A two, three, four or five‑point calibration can be performed by using the supplied (<0.1, 15, 100,
750 FNU and 2000 NTU) standards, user prepared formar in standards can also be used in all modes.
Calibration points can be modified when they are used.
GENERAL DESCRIPTION
GENERAL DESCRIPTION

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ABBREVIATIONS
NTU Nephelometric Turbidity Units
FAU Formazin Attenuation Units
FNU Formazin Nephelometric Units
ISO International Organization for
Standardization
LCD Liquid Crystal Display
RTC Real Time Clock
RH Relative Humidity
ID Identification
EBC European Brewery Comitee
Turbidityis the optical property that causes light to be scattered and absorbed, rather than transmitted.
The scattering of the light as it passes through a liquid is caused by the suspended solids. The higher
the turbidity, the greater the amount of scattered light. The molecules in a very pure fluid scatter light
to a certain degree, no solution will have zero turbidity.
The ISO 7027 Method specifies the key parameters for the optical system and the method to measure
the turbidity of water.
The HI88713 Turbidity bench meter is designed to meet or exceed the criteria specified by the
ISO 7027, DIN 38404 and NF EN 27027.
The light beam that passes through the sample is scattered in all directions. The intensity and pattern
of the scattered light is affected by many variables including the wavelenght of the incident light,
particle size and shape, refractive index and color.
The optical system of the HI88713 turbidity bench meter uses an IR LED, a scattered light detector
(900) and a transmitted light detector (1800).
PRINCIPLE OF OPERATION
The HI88713 Turbidity bench meter features G.L.P. (Good Laboratory Practice) functions that allow
traceability of the calibration conditions. The last calibration points as well as time and date
The HI88713 Turbidity bench meter has a user‑friendly interface with an easy to understand, graphical
LCD. Comprehensive contextual help is available at a simple key press. All messages and help screens
are available in several languages. Furthermore, a tutorial mode guides the user step by step through
the analysis process.
The HI88713 features a logging function that can hold up to 200 measurements in the internal
memory. Data can be viewed directly on the screen or it can be downloaded to a PC for further analysis
using the HI92000 Windows®compatible software.

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For the ratio turbidity mode, the microprocessor of the instrument calculates the NTU value, from the
signals that reaches the two detectors, by using an effective algorithm. The optical system and measuring
technique compensate the color interference and also the LED intensity fluctuations, minimizing the
need of frequent calibration.
For the FNU and NTU non ratio modes the turbidity is calculated from the signal that reaches the
scattered light detector (90°).
In FAU mode the turbidity is calculated from the signal that reaches the direct light detector, while in
NTU ratio mode the turbidity is obtained from signal ratio on scatter and transmitted light detectors.
The non ratio methods are more sensitive to the LED intensity fluctuations.
The lower detection limit of a turbidimeter is determined by the “stray light”. Stray light is the light that
reaches the detectors and is not caused by light scattering from suspended particles.
The optical system of HI88713 instrument is designed to have very low stray light, providing accurate
results for low turbidity samples. However, special care must be taken when measuring low turbidities
(see page 9 “General Tips for an Accurate Measurement” for sample preparation and measuring
techniques).
MEASUREMENT UNITS
The meter is using specific units according to the selected measurement mode. For NTU modes the
EBC unit option is available 1 EBC=0.245 NTU. When measuring in NTU modes a conversion to EBC
units is also available 0.245 NTU=1 EBC.

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ON
OFF
5
6
4
USB
POWER
12VDC
HI 88713 - ISO Turbidimeter
HELP
ESC CAL
RANGE RCL SETUP
LOG
0 - 1000 FNU
10 - 4000 FAU
0 - 980 EBC
0 - 4000 NTU
Turbidity
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INSTRUMENT DESCRIPTION
1) Liquid Crystal Display (LCD). The LCD has backlight for better visibility in dark environments.
2) Keypad. Splash proof resistant.
3) Cuvette Lid.
4) USB connector
5) 12 Vdc power input
6) ON/OFF switch
FUNCTIONAL DESCRIPTION

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4
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DISPLAY DESCRIPTION
The display contains the following fields:
1) Current time
2) Functional keys
3) Selected mode
4) Measuring units
5) Measured value
KEYPAD DESCRIPTION
The keypad contains 8 direct keys and 3 functional keys with the following functions:
Press to perform the function displayed above it. The function are screen releated.
Press to exit the current screen.
Press to access measurement modes.
Press to scroll up in a menu and help or to increment a set value.
Press to scroll down in a menu and help or to decrement a set value. Press to log the
current reading.
Press to access calibration menu.
Press to recall the log.
Press to display the help screen.
Press to access the setup menu.
ESC
RANGE
LOG
CAL
RCL
HELP
SETUP

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SPECIFICATIONS
FNU mode
Range 0.00 to 9.99; 10.0 to 99.9; 100 to 1000 FNU
Resolution 0.01; 0.1; 1 FNU
Accuracy ±2% of reading plus straylight
FAU mode
Range 10.0 to 99.9; 100 to 4000 FAU
Resolution 0.1; 1 FAU
Accuracy ±10% of reading
NTU ratio mode
Range 0.00 to 9.99; 10.0 to 99.9; 100 to 4000 NTU
0.00 to 9.99; 10.0 to 99.9; 100 to 980 EBC
Resolution 0.01; 0.1; 1 NTU
0.01; 0.1; 1 EBC
Accuracy ±2% of reading plus straylight
±5% of reading above 1000 NTU
NTU non ratio mode
Range 0.00 to 9.99; 10.0 to 99.9; 100 to 1000 NTU
0.00 to 9.99; 10.0 to 99.9; 100 to 245 EBC
Resolution 0.01; 0.1; 1 NTU
0.01; 0.1; 1 EBC
Accuracy ±2% of reading plus straylight
Range selection Automatic
Repeatibility ±1% of reading or straylight, whichever is greater
Stray Light < 0.1 NTU (0.05 EBC)
Light Detector Silicon Photocell
Method ISO 7027 Method
Measuring mode Normal, Average, Continuous.
Turbidity Standards <0.1, 15, 100, 750 FNU and 2000 NTU
Calibration Two, three, four or five‑point calibration
Light Source IR LED
Lamp life Instrument life
Display 40 x 70mm graphic LCD (64x128 pixels) with backlight
LOG Memory 200 records
Serial Interface USB
Environment 0 °C (32 °F) to 50 °C (122 °F); max 95% RH non‑condensing
Power supply 12 Vdc power input
Dimensions 230 x 200 x 145 mm (9 x 7.9 x 5.7”) L x W x H
Weight 2.5 Kg (88 oz.)

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Note: If you are using multiple cuvettes, always match the cuvettes.
CUVETTE HANDLING
The cuvettes should be free of scratches or cracks. Any cuvette with visible scratches should be
discarded. The cuvettes should be periodically washed with acid. After washing, the cuvettes should
be rinsed well with distilled or deionized water, multiple times. Allow cuvettes to air‑dry and store
them for long periods of time with theire caps, to avoid dirt entering inside. Always handle the
cuvette by touching only the cap or its top side (over the horizontal line).
Always store the cuvettes in separate boxes or with separators between them to avoid scratches
on the surface.
CUVETTE PREPARATION
Whenever a cuvette is used, it must be clean inside and outside. When it is placed into the instrument,
it must be dry outside, completely free of fingerprints or dirt.
GENERAL TIPS FOR AN ACCURATE MEASUREMENT
The HI88713 is a highly accurate bench too turbidity meter. Special care must be taken during
calibration and sample preparation to optimize the instrument performance and to fully benefit from
its features. Is very important for the analyst to use proper measurement techniques for accurate,
precise and repeatable readings. The instructions listed below should be carefully followed during
calibration and measurement to ensure optimum accuracy.
GENERAL RULES
• Always put the instrument on a flat, rugged surface when taking measurements.
• Do not operate in direct sunlight.
• Keep the lid of the instrument closed when it is not used to prevent dust or dirt entering inside.
• Always close the cuvette lid during measurement.
• Always use cuvettes without scratches or cracks because they can cause inaccurate readings.
• Always cap the cuvettes to prevent the sample from spilling
• To prevent contamination of the optical system, do not use to much oil.
• When using multiple cuvettes, they should be indexed and matched, when possible.
CUVETTE
The cuvette is part of the optical system in all measurements. The light reaches the sample by passing
through the cuvette glass. As a result, the measurement can be affected by the glass imperfections,
dirt, dust, scratches, or fingerprints present on the cuvette surface. Special care must be taken in
preparing and handling the cuvette.

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If the cuvette is not indexed, use the factory marking to align the cuvette with the marking on the
cuvette holder.
CUVETTE OILING
To hide minor imperfections and scratches, the cuvettes should be oiled outside with the supplied
silicone oil. This is very important, especially for low turbidity samples (< 1 FNU), otherwise scratches
can contribute and alter turbidity readings.
The silicone oil has the same refractive index as the glass and will not alter the turbidity readings. It
is important to apply only a thin layer of silicone oil.
Warning: Do not apply silicone oil in excess because it may retain dirt or contaminate the cuvette
holder of the instrument, altering the turbidity readings.
It is very important to apply the silicone oil on a clean, dry cuvette. Apply a few drops of oil and wipe
the cuvette thoroughly with a lint‑free cloth. Wipe off the excess oil till you obtain a thin, uniform
layer. If the procedure is correctly followed, the cuvette should appear nearly dry with no visible oil.
Note: The supplied cloth for oiling should be stored together with the silicone oil bottle and cuvettes,
taking care to avoid contamination with dirt. After a few oiling procedures, the cloth will contain
enough oil to wipe the bottle with it without adding more oil. From time to time add some
drops of oil on the cuvette to provide the necessary oil quantity in the cloth.
INDEXING A CUVETTE
It is very important for low turbidity readings to always insert the cuvette into the instrument in
the same position. All cuvettes are factory indexed. The factory mark on the cuvette can be used to
align the cuvette with sign on the cuvette holder.
10 ml
10 ml
10 ml
CUVETTE PREPARATION
Whenever a cuvette is used, it must be clean inside and outside. When it is placed into the instrument,
it must be dry outside, completely free of fingerprints or dirt.

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To further reduce the effect of glass imperfections, the cuvette can be indexed and use this new index
as the position mark. For indexing one cuvette or matching multiple cuvettes, the continuous reading
mode is suggested. In this mode multiple successive readings are taken without turning off the lamp.
The turbidity is immediately displayed, reducing considerably the measurement time.
Note: The instrument can not perform continuous readings if the average mode is on.
In order to index a cuvette follow the next steps:
• Fillthecuvettewithhighqualitywater(<0.1FNU)
up to the 10 mL mark.
•Clean and oil the cuvette as described in the
previous section.
• Turn the instrument ON.
•Insert the cuvette into the instrument and press
“Read” functional key. Record the reading.
•Open the instrument lid, slightly rotate the
cuvette and take a new reading.
• Repeat the previous step until you read the lowest value.
• Alternatively, press and hold the “Read” key to make continuous readings. After the first value
is displayed, open the lid and start rotating the cuvette until the lowest value is displayed.
10 ml
10 ml
10 ml
10ml
10 ml

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10 ml
10 ml
10 ml
10ml
10 ml
• Mark this position on the white band at the top
of the cuvette with a water resistant pencil.
• Always use this position to align the cuvette with
the mark on the cuvette holder.
In order to match multiple cuvettes follow the
next steps:
•Fill multiple cuvettes with high quality water
(<0.1FNU) up to the 10 mL mark.
• Clean and oil the cuvettes as described before.
• Turn the instrument ON.
• Insert the first cuvette into the instrument
and press “Read” functional key. Record the
reading.
• Open the instrument lid, slightly rotate the
cuvette and take a new reading.
• Repeat the previous step until you read the
lowest value.
• Mark this position on the white band at the top
of the cuvette with a water resistant pencil.
10ml
MATCHING MULTIPLE CUVETTES
Precise measurements require the use of a single cuvette. If it is not possible, cuvette selection and
matching must be performed before taking measurements.
10ml
1

• Open the instrument lid, slightly rotate the
cuvette and take a new reading.
• Repeat the last step for the second cuvette until the reading is within 0.01 FNU of the value
obtained for the first cuvette.
•Alternatively, press and hold the “Read” functional key, after the first value is displayed, open
the lid and start rotating the cuvette until the read value matches the first cuvette.
• Mark this position on the second cuvette with a water resistant pencil.
• Follow the same procedure for all the cuvettes you need.
Note: If the cuvette is indexed, use the index to position it in the instrument.
SAMPLING TECHNIQUE
When taking turbidity measurements it is very important to select a representative sample. For
consistent results, follow the next tips when sampling:
• Gently mix the water before taking the sample.
• If the sample is taken from a pipe, discard the first few liters.
• If measuring a non uniform source, collect samples from different places and mix them.
When measuring the collected sample, keep in mind the following:
•Samples should be analyzed immediately after collection because the turbidity can change in
time.
•To avoid dilution of the sample it is better to rinse the cuvette with a quantity of sample and then
discard. Then you can fill the cuvette with sample.
• Pay attention that cold samples do not condense on the sample cell.
REMOVING AIR BUBBLES
Any air bubbles present in the sample will cause high turbidity readings. To obtain accurate
measurements, remove the air bubbles using one of these methods:
10ml
2
•Insert the second cuvette into the instrument and
take a reading.
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• Application of a partial vacuum;
• Addition of a surfactant, such as Triton X‑100;
• Use of an ultrasonic bath;
• Heating the sample.
Sometimes it is necessary to combine two or more methods for efficient air bubble removal.
Note: Each method can alter the sample turbidity, if misused, so they have to be used with caution.
APPLICATION OF VACUUM
Vacuum works by decreasing the atmospheric pressure. The bubbles from the solution come out to the
surface. Application of vacuum is a very simple procedure andany vacuum can be used. The simplest
equipment is a syringe and a rubber stopper.
Notes: • Pay attention that the vacuum equipment be clean and oil‑free.
• It is not recommended to apply vacuum to a viscous sample that contains volatile com‑
ponents. The vacuum can disrupt the volatile components and increase the bubbles in
the sample.
ADDITION OF SURFACTANT
Surfactant changes the surface tension of the water. This causes the bubbles to be released from the
sample. This method is effective for samples that are supersaturated with air.
The procedure consists in the addition of a drop of surfactant in the cuvette before adding the sample
to be analyzed.
A common surfactant used for degassing is Triton X‑100.
Warning: Changing the surface tension will cause a rapid settling of particles that cause turbidity.
To avoid this problem, analyze the sample as soon as possible.
Do not shake the sample vigorously because the surfactant may foam. Always rinse the cuvette before
adding a new sample to avoid surfactant accumulation.
Surfactant contribution to the turbidity readings is negligible.
Note: Surfactant addition should be used for degassing only when other methods are ineffective.
USE OF AN ULTRASONIC BATH
The ultrasonic waves are very effective in removing air bubbles from samples. However, ultrasonic waves
should be used with care because they can alter the samples turbidity characteristics, by modifying
the shape and size of particles which cause turbidity. The ultrasonic waves can also break the existing
air bubbles, leading to a complication in the degassing process.
In order to avoid excess application of the ultrasonic waves use the ultrasonic bath until all visible air
bubbles are removed, and then measure the turbidity. This is the most used procedure for degassing.
If you are not sure that all air bubbles were removed, apply ultrasonic waves again for a short period
of time and then measure the turbidity. Repeat this procedure until the turbidity is increasing instead
of decreasing, sign that turbidity of the sample was altered.

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STARTUP
The HI88713 Turbidity bench meter is supplied with all necessary accessories.
Unpack the instrument and place it on a flat surface. Do not place the instrument in direct sunlight.
Insert the 12 Vdc power plug into its input on the back of the instrument.
Switch on the instrument. On the LCD, the Hanna Instruments Logo will appear for a short time,
followed by the main screen for turbidity measurements.
The instrument loads the selected language. If no language can be loaded the instrument will work
in the “safe mode”. In “safe mode” all the messages are displayed in English and tutorial and help
information are not available.
In order to degas a sample, fill a clean cuvette with sample and immerse it (1/2 to 2/3 immersed)
in an ultrasonic bath. Follow the degassing procedure described above. Only after the degassing
procedure is finished the cuvette can be capped.
HEATING THE SAMPLE
This procedure can be very effective however it should be handled with care because it can alter the
turbidity of the sample. When heating a sample, the volatile components from the sample can vaporize,
the suspended components can dissolve or the sample characteristics can change.
The heating procedure should be used with extreme care.
Use a warm water bath and immerse the cuvette filled with sample into the bath. Heat the sample
only until the visible bubbles are removed.
Note: Always cool the heated sample to the original temperature before measurement.
The heating procedure can be used in combination with vacuum or ultrasonic waves application for
a more effective air bubble removal.

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The HI88713 bench‑top Turbidity meter has a unique Tutorial Mode that provides additional information
to help the unexperienced user during the measurements. The instrument displays a screen, with
explanations and confirmation button, when a preparation or other operation has to be performed by
the operator. The instrument resumes the measuring sequence when the operator confirms that the
requested operation was done.
To disable this mode, when in the main screen,
press the SETUP key to enter the setup, and
then press DOWN key until the “Tutorial” line is
highlighted. Press the “Disable” key then press
ESC to return to the main screen.
RANGE SELECTION
The HI88713 bench‑top Turbidity meter has four measuring modes: FNU, FAU, NTU Ratio and NTU
Non Ratio. When the instrument is in the main
screen, the selected mode is displayed in the right
side of the LCD, on the message line.
To change the mode, press the RANGE key.
When the display shows the Change mode screen,
use the UP or DOWN key to select a new mode .
Press “CFM” key to select the new mode. The
instrument returns to the main screen.
RANGE
LOG
TUTORIAL MODE
SETUP

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HELP MODE
The HI88713 bench‑top Turbidity meter offers an interactive contextual help that assists the user
at any moment.
To access help screens, just press HELP.
A screen with additional information will appear. To read
all available information, scroll down or up text using the
UP or DOWN key.
Press the “Support” key to access a list of the Hanna
Instruments support centers and their contact information.
Press the “Accessories” key to view a list of the instru‑
ments accessoies.
To exit support or accessories screens, press ESC, and
the instrument will return to the previous help screen.
To exit help mode just press the HELP key again and the
meter will display the previous screen.
MEASUREMENT PROCEDURE
When taking turbidity measurements, several basic rules should be followed:
• Always use cuvettes without scratches or cracks because they can cause inaccurate readings.
• Always cap the cuvettes to prevent spillage of the sample from spilling the instrument.
• Always close the cuvette cover during measurement.
• To prevent contamination of the optical system, do not use too mush silicon oil.
To take turbidity measurements:
• Turn the instrument ON by pressing ON/OFF.
When dashes are displayed on the LCD, the
instrument is ready. The current time appears
in the upper left corner of the display and the
mode name appears on the right side of the
LCD, in the message line.
• Fill a clean, dry cuvette with 10 mL of sample
up to the mark, only handle the cuvette by the
top.

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NORMAL MEASUREMENT
This type of measurement is best suited for regular readings, when the sample is stable and normal
accuracy is required. In normal mode, the measurement takes about 10 seconds and the lamp is ON
for a minimum period of time (about 7 seconds).
CONTINUOUS MEASUREMENT
This measurement mode is suitable when many measurements have to be taken in a short period of
time. The mode is useful to evaluate a very fast settling sample. This measurement mode is recom‑
mended for indexing cuvettes.
• Press “Read” functional key to take the mea‑
surement.
The display will show “READ” in the left side and
blinking dashes. The dashes and light icon will
appear during different measurement phases.
• The result is displayed in the selected units.
10 ml
10ml
10 ml
• Replace the cap.
• Wipe the cuvette thoroughly with a lint‑free
cloth to remove any fingerprints, dirt or water
spots.
• Apply silicone oil on the cuvette and wipe with
a lint‑free cloth to obtain an even film over the
entire surface of the cuvette.
Note: It is very important to oil the cuvette, espe‑
cially for low turbidity values (< 1 FNU)
to hide the glass imperfections which can
influence the reading.
• Place the cuvette into the instrument. Align
the mark from the cuvette with the sign on the
instrument top
• Close the lid.
Note: If you have a cuvette with indexing mark,
place the cuvette into the instrument with
the indexing mark aligned with the sign on
the instrument top.

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•Press “Read” functional key to take the mea‑
surement.
The display will show “READ” in the left side and
blinking dashes. The dashes and light icon will
appear during different measurement phases.
The first value is displayed after 10 seconds and
then a new average of the available readings
is displayed each second. When a new value
is displayed, the measurement value will blink
briefly. The last averaged value remains on the
display at the end of the measurement.
• Press “Read” functional key and keep it pressed to take continuous readings.
The display will show “READ” in the left side and blinking dashes. The dashes and light icon will
appear during different measurement phases. The first value is displayed after 10 seconds and then
a new reading is displayed each second as long as the “Read” functional key is kept pressed. When
a new value is displayed, the measurement value will briefly blink.
The last value remains on the display after the “Read” functional key is released.
AVERAGED MEASUREMENT
This measurement mode is useful when samples that cause unstable readings are analyzed. By
averaging several readings, noise effect is reduced and accurate measurements can be taken.
This mode can also be selected when high accuracy measurements are needed. In the average mode
10 measurements are averaged in a short period of time (about 20 seconds).
To use the averaged reading mode first enter setup and enable the Average reading mode. The “AVG”
text will be displayed in the left side of the screen.
The HI88713 Turbidity bench meter automatically
selects the correct turbidity range to display the
results with the highest accuracy. In FNU and NTU
Non‑Ratio Turbidity Modes, if the measured value
is higher than 1000 FAU, the display will show
the maximum value blinking and the message
“Out of range” on the message line. For FAU
Turbidity and NTU Ratio Turbidity modes, if the
measured value is higher than 4000 FNU/NTU
(980 EBC), the display will show the maximum
value blinking and the message “Out of range”
on the message line.

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CALIBRATION PROCEDURE
The HI88713 Turbidity bench meter is supplied with 5 AMCO Hanna standards (<0.1 FNU, 15 FNU,
100 FNU, 750 FNU and 2000 NTU) that are specially designed for NTU ratio mode.
The calibration can be done using the supplied calibration solutions for NTU Ratio mode or user
prepared standards for all modes. Turbidity standards have a shelf life and should not be used after
the expiration date. Alternatively, formazin standards can be used. It is recommended that the turbidity
value of the prepared calibration solutions to be close to the default calibration points.
The first calibration point should be near 0 FNU, the second point can be chosen between 10 and 20
FNU, the third point between 50 and 150 FNU, the fourth point between 600 and 900 FNU and the
fifth point between 1500 and 2500 NTU.
FORMAZIN PREPARATION
In order to prepare formazin 4000 NTU stock solution, follow the next procedure:
Solution I : Dissolve 1.000 gram of hydrazine sulfate, (NH2)2 H2SO4, in distilled, deionized water
and dilute to 100 mL in a volumetric flask.
Warning: Handle hydrazine sulfate with care because it is a carcinogen reagent. Avoid inhalation,
ingestion, or skin contact. Formazin solution can also contain some hydrazine traces.
Solution II : Dissolve 10.000 grams of hexamethylenetetramine, (CH2)6N4, in distilled, deionized
water and dilute to 100 mL in a volumetric flask.
Stock solution: Mix 10 mL Solution I and 10 mL Solution II in a flask. Let the stock solution stays
48 hours at 25±3°C (77±5°F). This will result in a 4000 NTU formazin suspension. It is very
important for the formation of the formazin polymer to maintain the same temperature.
The stock solution (4000 NTU) can be stored up to one year in proper conditions. Store formazin in
amber glass bottle or any UV‑light blocking bottle.
To obtain a high quality formazin always use pure reagents and high‑purity water.
To prepare the calibration standards, dilute the stock solution with the same high‑purity water you
used for the preparation of the stock solution. The diluted formazin solutions are not stable. They
should be used immediately after preparation and discard immediately after use.
UNITS CHANGE (only for NTU Ratio and NTU Non-Ratio modes)
To change the units for NTU Ratio and Non‑Ratio modes, simply press the “Unit” functional key
when a measurement is available. The EBC value is obtained by multiply with 0.245 the NTU value.