ATAGO NAR-2T User manual

Abbe Refractometer
Instruction Manual Cat.No.1220
1220-E28
PRODUCT REGISTRATION & WARRANTY CARD
https://www.atago.net/registration/
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(1) Preparation of refractometer13
(2) Connection with circulating constant temperature bath15
Contents
1
Page
Precautions for use2
Refractive Index and Brix8
Unpacking and Setting-up9
Names and Functions of main parts
Power-on17
Calibration (Scale adjustment)
Finding average dispersion value and Abbe number37
Cleaning and maintenance42
Replacement of consumable supplies and component parts
(Simultaneous analysis of insoluble solids, sugar and water)
(1) Measuring glass, plastic samples25
(2) Measuring film samples28
(3) Measuring of double refraction samples30
Preparation for measurement
12.
13.
14.
6.
7.
1.
2.
3.
4.
5.
(1) Main unit of NAR-2T 10
(2) Digital thermometer12
(3) How to use Illuminator Selector Switch12
Measurement of liquid sample238.
(1) When measuring colored or cloudy sample35
(2) Discoloration or "Burning" of the main Prism35
(3) Measurement method of pasty sample35
(4) For measuring liquid sample containing insoluble solids36
Measurement of solid sample
9.
(1) Calibration with distilled water18
(2) Calibration with test piece20
Measurement of powdered sample3310.
Situations that may require additional attention
11.
Relation between Brix percent and Refractive Index (nD)49
Temperature correction table for sucrose solution50
Specifications 51
Repair and warranty52
ATAGO CO.,LTD. Service Center53
15.
16.
17.
18.
19.
(1) Prism 44
(2) LED lamp46
(3) Thermo-sensor unit47
(4) Desiccant48

Introduction
1. Precautions for use
For safe use --- Be sure to observe the following.
2
Explanation of indications
WARNING
CAUTION
Explanation of symbols
This symbol denotes an item which you are warned (or cautioned) of.
The contents of warning are described in detail in or near the ڹ.
This symbol denotes an action which you must not do (a prohibited item).
The contents of prohibition are described in detail in or near the ۑ.
This symbol denotes an action you must do.
The contents of instruction are described in detail in or near the ە.
Thank you for purchasing the "ATAGO, Abbe Refractometer NAR-2T". Before using your NAR-2T,
read this instruction manual carefully and understand how to use it. After reading this manual,
keep it on hand for future reference.
In this manual "For safe use" describes the important items necessary for safety. Read it
carefully.
This operation manual describes the items which you are required to observe in order to use
the NAR-2T safely to prevent injury to you and other people and damage to your property.
The explanation of the indications and symbols of those items are as follows. Understand them
first and then read the following pages to use your NAR-2T correctly.
If this indication is neglected and the instrument is handled
incorrectly, the user may be seriously injured and may result
in death.
If this indication is neglected and the instrument is handled
incorrectly, the user may be injured and the user's property
may be damaged.

Handling of this instrument
ە
ە
ە
ە
ە
3
WARNING
CAUTION
ە
When measuring a substance harmful to
the human body, be well aware of its
properties and put on protective gloves,
mask, etc.
If the instrument begins to smell
abnormally, overheat, or emit smoke, turn
off the power switch and disconnect the
power plug immediately.
Fire or malfunction may result if the
instrument is continued to be used.
Ask your ATA G O distributor for an inspection.
Do not attempt to repair, modify, or
disassemble the instrument yourself.
Improper servicing may result in fire,
electrical shock, or burns.
If the instrument is dropped or is subjected
to a strong shock, have it inspected by an
ATAGO distributor.
Fire or malfunction may result if the
instrument is used.
Do not apply water or sample over any part
other than the surface of the prism.
Application on any other part of the
instrument may result in a malfunction.
If this instrument is used to measure very
hot or highly acidic sample, the prism may
be damaged resulting in inaccurate
measurements.
1. Precautions for use

Handling of this instrument (Continued)
4
CAUTION
ە The prism is made of optical glass. Do
not tap or contact its surface with any
metal tool such as a spoon or
tweezers.
If the surface of the prism is damaged,
inaccurate measurements will occur.
ە After taking a measurement, completely
wipe off any sample on the surface of the
prism and surrounding area with tissue
paper soaked in water.
Then remove any remaining moisture
completely with dry tissue paper.
ە If you have measured a sample of
polymer or fats and oils, wipe it off with
tissue paper soaked in alcohol or
neutral detergent.
Then remove any remaining moisture
completely with dry tissue paper.
ە Always turn off the power switch after
use.
ە When transporting the instrument,
place it in its original box.
Carefully read this instruction manual and fully understand the function and operation of
each part of the instrument before use.
Check that each part of the instrument operates normally before use.
Check the necessary operations such as calibration according to the instruction manual.
The manufacturer shall not be held responsible for any or all damages as a result of use
of the instrument for those other than its intended purposes (measurement of Brix, Refractive
Index, Concentration).
The prism mounted on the sample stage that is in contact with a sample under measurement
is a consumable item.
Ensure that if use of the instrument has undesired effects on the consumption of the
measured materials, etc., ATAG O shall not be held responsible for the result.
ە
ە
ە
ە
ە
ە
1. Precautions for use

Handling of plug
5
WARNING
CAUTION
ەDon't plug the power cable into an outlet
other than AC100 to 240V.
Inserting the power plug in any other
outlet may result in shortcircuiting the
unit, smoking or fire.
ەDo not use the power cable if damaged
or broken.
If used, fire, electrical shock, or burns
may result.
For a new power cable, contact your
ATAGO distributor.
ەDo not insert or disconnect the power
plug with wet hands.
ەBe sure to hold and pull the plug when
disconnecting the power cable from the
outlet.
If the cable is pulled improperly, the plug
may be broken, and may result in fire or
electrical shock.
1. Precautions for use

Connection of circulating constant temperature bath
6
WARNING
ەFor connecting a circulating constant
temperature bath with the refractometer,
make sure to use the elicon tube (made
of vinyl chloride).
Moreover, tightly fasten each joint part
between the nozzle and tube with the
tie band.
ە The temperature of hot water to be
supplied from a circulating constant
temperature bath to this refractometer
is limited to 120Υ, and the flow rate of
the circulating constant temperature
bath should be 10 L/min. at maximum
through a nozzle of 6mm caliber.
To o much discharge not only increases
water pressure but also may cause
disconnection between the nozzle and
tube or may overload the water channel
inside the refractometer.
ە If the tube is damaged, replace it with
new one as immediately as possible.
If the damaged tube is continuously used,
the operator may scald himself with hot
circulating water.
ەPay careful attention to hot circulating
water.
1. Precautions for use

7
Items to be observed when using
1. Precautions for use
ە Do not drop the instrument or subject it to any strong shock.
ە The power cable may be damaged if mishandled in any of the following ways.
࣭Bending the cable.
࣭Pulling the cable.
࣭Twisting the cable.
࣭Placing the cable under heavy objects.
࣭Catching the cable between objects.
ە If the instrument becomes dirty, wipe it with a soft cloth.
ە Do not use benzine, paint thinner, etc. to clean the instrument.
Environmental conditions
Handling
Daily maintenance
ە Use the instrument at an altitude below 2,000m (above sea level).
ە Use the instrument indoors.
ە Use the instrument on a flat and level surface such as a desk or table.
ە Use the instrument where the temperature is between 5 to 40䉝.
ە Do not leave the instrument in a location exposed to direct sunlight or near a heating unit
where the temperature may rise.
ە Do not change the environmental temperature of the instrument suddenly.
ە Do not place the instrument in a place where it may be subject to strong vibrations.
ە Do not use the instrument where there is much dust.
ە Do not leave the instrument where the temperature is extremely low.
ە Do not leave the instrument in a damp place.
ە Do not place or drop heavy objects on the instrument.
ە Use the instrument under the condition where humidity is 80% at 31䉝or lower, falling linearly
to 50䠂at 40䉝.
ە Main supply voltage fluctuation should not to exceed 㼼10% the nominal voltage.
ە Installation categories (Overvoltage Categories): 䡈䡈
ە The pollution degree is 2 (according to IEC60664).

When light goes to medium Ȯthrough air with an
Refractive Index of air in the atmospheric pressure
assumed as 1, the ratio of the sine of incident angle
Șagainst the interface to the sine of refractive
angle șis called the Refractive Index of the medium.
Since the Refractive Index changes due to the
temperature, and wavelength of light, it is expressed
as follows:
1. What is a refractometer?
2. Refractive Index and Brix
8
If you put a straw into a glass of water, the straw appears bent. If the water contains
concentrations of sugar, the straw will appear more bent. This is called the "phenomenon of
light refraction". The refractometer applies this principle (if a solution has a higher concentration,
its Refractive Index rises proportionally). The refractometer is a measuring instrument devised
by Dr. Ernst Abbe in Germany in the early 20th century.
2. What is Refractive Index?
3. Brix scale
Note:
The scale of the NAR-2T is a Brix scale that is based on the Refractive Index of water
(nD=1.33299=Brix 0.0%). Brix means the scale of the weight (%) of sucrose (grams of
sucrose contained in 100 grams of sucrose solution). Thus, if a sucrose solution is
measured, it matches this concentration. However, almost all foods contain not only sugar,
but also a variety of dissolved components such as salt and protein. The total
concentration of these water-soluble materials is called the soluble solid content. When
this sample is measured, Brix is almost consistent with the soluble solid content (%) and is
used as a practical scale.
* The Brix scale is expressed in % mass (Sucrose) as the International System of Units
(SI unit).
For example, the Refractive Index of water at 20Υ
for the D line is expressed as ࠉ= 1.33299
(generally it is expressed in the form of nD=1.33299).
For relation between Brix percentage and refractive and Refractive Index (nD),
refer to page 49.
boundary
air
mediumȮ
Ș
ș
㹬 =1
㹬=
sin Ș
sin ș
n20
D
n
t
D
n : Represents the Refractive Index
t : Te m perature(Υ)
D : D- line of sodium
Note: The Refractive Index measured by setting the
Refractive Index of vacuum to 1 is called the
absolute Refractive Index, but it is generally
scarcely used.

●Abbe Refractometer NAR-2T (main unit) ………………………………1
●Digital thermometer………………………………………………………………1
●AC Power cable……………………………………………………………………1
●Lamp cable( LED lamp : 2) …………………………………………………1
● Test piece ………………………………………………………………………1
● Contact liquid (monobromonaphthalene)………………………………1
● Instruction manual (this book) …………………………………………………1
● Inspection certificate………………………………………………………1
3. Unpacking and Setting-up
9
1. Unpacking
2. Setting-up
a)
b)
Take all contents out of the packing case and check every item whether there is any damage
exteriorly or not.
Confirm the contents so that the following articles have been contained in the package
without lack.
a)
b)
c)
d)
Connect this refractometer to a mains outlet of AC100 to 240V, 50/60 Hz.
Set this refractometer in a place where it can be operated at an ambient temperature from
5 to 40℃.
Since this refractometer has extremely precise component parts inside, set it in an optimum
place where it is free from direct rays of the sun, strong vibration, dust, corrosive gas, heat
source.
Set this refractometer on a solid and level surface of a warkbench, etc. When setting, be
very careful not to give a strong shock to it.

Fig. 4-1 Fig. 4-2
4. Name and functions of main parts
(1) Main unit of NAR-2T (Figs. 4-1, 4-2 and 4-3)
The field of refraction view and the field
of scale view can be observed through
the eyepiece. When the lamp is on, the
field of scale view is brightly and clearly
observed through the eyepiece as shown
in Fig. 7-5 on page 21. In the upper part of
Fig. 7-5, the boundary line to be seen
between bright part and dark part
appears only when the measurement
knob is properly operated with a sample
on the main prism.
a) Eyepiece
When measuring liquid sample, use this
light to illuminate a sample through the
secondary prism. For measuring solid
sample, utilize another light source such
as the natural light or a proper lighting
apparatus.
b) Sample illuminator lamp holder
d)-a, d)-b Prism open/shut handles
When pouring or putting sample on the
main prism, the secondary prism must
be opened in advance. Since the
secondary prism functions to illuminate
the sample uniformly, its surface to
contact the sample is frosted to diffuse
the light uniformly. The standard
clearance between the main and
secondary prisms is 0.2mm.
e) Secondary prism
10
The main prism is the most important
component for measurement. Pay
careful attention to it neither to get it
damaged nor to get it corroded. A
sample is set on the main prism for
measurement. The frames of both the
main and secondary prisms are made of
stainless steel that has strong corrosion
resistance characteristic.
f) Main prism
a) d)-b d)-a
When this handle d)-a is turned to the
front side, the secondary prism is raised
upwards by about 1cm. If the handle d)-b
is turned left side, the secondary prism is
opened because this handle serves as a
lever to move the secondary prism. After
measurement of a high viscous sample,
b)
e)
f)
g)
h)
i)
j)
k)
l)
m)
n)
the secondary prism can be detached
from the main prism smoothly without
unreasonable force thanks to the
abovementioned function of the handle
d)-a.
c)
j)
c) Sample illuminator lamp arm
Direction and hight of sample illuminator
lamp holder can be adjusted.

11
j) Nozzles for constant temperature
circulating bath
The color compensator knob is used to
achromatize the boundary line
appearing in the field of refraction view.
This knob also serves as the dispersion
scale, in other words, average
dispersion value (nF-nC) can be known
by reading this scale as the boundary
line is achromatized.
m) Color compensator knob
(dispersion scale)
These nozzles serve to carry constant
temperature water into the periphery of
the prism unit. There is a nozzle on
each of the right and left sides of the
main prism and two nozzles in front of
the secondary prism.
h) Scale field illuminator
Tu r n the measurement knob to set the
boundary line appearing in the field of
refraction view to the cross hairs.
Interlocking with the measurement
knob, the scale indicates the Refractive
Index or Brix percent of the sample.
n) Measurement knob
The serial number and ratings of the
refractometer are shown on this label.
o) Rating label
Fig. 4-3
4. Names and Functions of main parts
The thermo-sensor that is screwed in the
main prism from the side always
measures the temperature of the main
prism.
g) Thermo-sensor
This lamp illuminates the scale field.
With lighting of this lamp, the black
scale and indication line engraved on
the glass plate are clearly seen in the
orange field of view.
Desiccant tablets inside the desiccant
case can be seen through the glass
window of the case.
The green color of the desiccant
gradually fades as it gets close to
saturation.
When it becomes pale green, turns the
lid counterclockwise to open and
replace it with a new one.
i) Desiccant case
MODEL㸸
INPUT㸸
DATE㸸
Serial No㸸
For reflecting measurement, remove the
cap of this lighting hole to let in a light
for illuminating the sample indirectly.
k) Lighting hole for reflecting
measurement
l) Calibration screw (scale adjustment)
The head of the calibration screw is
seen in the center of this metal ring
(calibration section). For calibrating the
scale, turn this screw with a
screwdriver.
o)

Fig. 4-4
The light intensity can be selected from
eight levels, and also the light intensity of
the scale view can be selected from three
levels with these switches (UP and DOWN).
a) Illumination selector switch
b) Main power switch
(2) Digital thermometer (Figs. 4-4 and 4-5)
a)
12
Υ
UP DOWN
UP DOWN
(3)-1. How to select the light intensity (from eight levels)
Digital thermometer displays the level of the light intensity (0 to 7) by pressing UP or
DOWN switch when the digital thermometer displays the current temperature.
*0 means the light is off.
a)
Illumination selector switch
ەAbout error messagesە
4. Names and Functions of main parts
Tu r n this switch ON and the refractometer
and the digital thermometer are turned on.
Fig. 4-5
c) Main power connector port
Plug the AC power cable into this
connector port.
d) Thermo-sensor cable connector port
Plug the thermo-sensor cable connector
of the Abbe Refractometer into this
connector port.
e) Lamp cable connector port
Plug the lamp cable connector of the
Abbe Refractometer into this connector
port.
(3) How to use Illuminator Selector Switch
Press UP to get more intensity of the light, and press DOWN to
get less intensity of the light.
b)
After selecting the level of the light intensity, the digital
thermometer displays the current temperature in 5 seconds
Also, the digital thermometer displays the current temperature
when the switchs are not operated for 5 seconds.
c)
(3)-2. How to select the light intensity of the scale view (from three levels)
Press UP and DOWN switchs together when the digital thermometer displays the
current temperature. The digital thermometer displays the level of the scale light
intensity (C0 to C2).
a)
By pressing UP or DOWN, the display changes to C0, C1 or C2, and the scale light
intensity changes. *C0 means the scale light is off.
b)
After selecting the level of the scale view light intensity, the digital thermometer
displays the current temperature in 5 seconds. Also the digital thermometer displays
the current temperature when the switches are not operated for 5 seconds.
c)
The unit displays error messages when there is some problems or the unit is operated wrong.
ࠕEEEࠖis displayed when the temperature sensor cable is not connected, or the unit
does not work properly.
ࠕLLLࠖis displayed when the temperature gets below 0Υ
b)
c)
d)
e)
When you can not specify the problem with the information above, please contact your
ATAGO distributor.

Fig. 5-2
13
Note : The articles marked with asterisk (*)
are not supplied as accessories to
NAR-2T.
5. Preparation for measurement
(1) Preparation of refractometer
Make sure the power is off. Set the
refractometer with the prism unit in the
front on a workbench or proper table
(Fig. 5-3 on page14).
a)
Plug the thermo-sensor cable connector
into the thermo-sensor cable connector
port on the real panel of the digital
thermometer.
b)
Set the lamps supplied as accessories in
the two lamp connector of the lamp
cable (Fig. 5-1).
c)
Insert the lamp connector
respectively into the holders of the
sample illuminator lamp arm and on
the left side of the main body.
d)
Fig. 5-1
図5-1
WARNING
●
●
Don't plug the power cable into an outlet of specified mains supply of AC100 to 240V.
Otherwise, it may cause smoke, fire or serious damage to the refractometer.
If the power cable (plug) is damaged, modified, or broken, don't use it. If such a cable
(plug) is used, it may cause electric shock or fire.
For repairing or replacing the cable (plug), ask the dealer or our distributor to do it.
CAUTION
●
●
Don't touch the plug with wet hand.
When disconnecting the power cable from the outlet, make sure to do it by holding the
plug. If the cable is pulled for disconnection, it may not only break the cable but also
cause fire and electric shock.
Two lamp connectors are different
in the shape. Insert the lamp
connector to the connect position
(Fig. 5-2).
Note :
Make sure the two lamps (Fig. 5-1).
Fig. 5-1
LED lamp
Lamp cable

To AC outlet
14
5. Preparation for measurement
*Circulating constant
temperature bath
*Water *Alcohol
*Sample
*Note
Digital thermometer Refractometer
Contact
liquid
Te s t
piece
Fig. 5-3
Plug the lamp cable connector into the
lamp cable connector port on the rear
panel of the digital thermometer.
e)
f) Plug the AC power cable into the main
power connector port on the rear panel
of the digital thermometer. Then plug
the AC power cable into an AC100V to
240V mains outlet and turn the power
switch on. The digital thermometer
indicates the current temperature of
the main prism.
g) With the illumination selector switch
provided on the upper side of the
digital thermometer, the light quantity
of the Abbe Refractometer's lamp
can be selected in eight steps of UP
and DOWN (refer to page 12).
Note : The articles marked with asterisk (*) are not
supplied as accessories to NAR-2T.

(2) Connection with circulating constant temperature bath
WARNING
15
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Pay careful attention to hot circulating water.
For connecting a circulating constant temperature bath with the refractometer, make
sure to use heat-resistant flexible tube which can stand at 150Υor higher.
Moreover, tightly fasten each joint part between the nozzle and tube with the tube
band.
If the tube is damaged, replace it with new one as immediately as possible.
If the damaged tube is continuously used, the operator may scald himself with hot
circulating water.
The temperature of hot water to be supplied from a circulating constant
temperature bath to this refractometer is limited to 120Υ, and the flow rate of the
circulating constant temperature bath should be 10 L/min. at maximum through a
nozzle of 6mm caliber.
To o much discharge not only increases water pressure but also may cause
disconnection between the nozzle and tube or may overload the water channel
inside the refractometer.
Refractive indices of liquid matters vary depending on the temperature. Therefore, it is
strongly recommended to use a circulating constant temperature bath together with the Abbe
Refractometer for stable measurement at a constant measurement temperature as well as
for obtaining possibly correct results.
There are water circulating channels provided by the main and secondary prisms, and
constant temperature water is carried through tubes connected with the four nozzles shown
in Fig. 5-4. The following explains the method to connect the Abbe Refractometer with the
circulating constant temperature bath.
5. Preparation for measurement
Prepare three pieces of tubes (a, b, c) for
connection with a circulating constant
temperature bath as specified below.
Tu b e a and Tu b e c : 90cm long each
Tu b e b : 20cm long
a)
Connect the tube a and tube c to the
water outlet and inlet of the circulating
constant temperature bath, and fasten
them with tie bands.
b)
Connect the other end of the tube a
connected to the water outlet of the
circulating constant temperature bath to
the IN1 nozzle of the refractometer. Next,
connect the nozzles IN2 and OUT1 with
the tube b of 20cm long. Lastly, connect
the other end of the tube c connected to
the water inlet of the circulating constant
temperature bath to the nozzle OUT2.
Fasten every joint with a tie band.
c)
Note:Use heat-resistant flexible tube which
can stand at 150Υor higher and
whose outer diameter is 12 to 13 mm
and inner diameter is 6 to 7mm.
Tu b e a
Tu b e c
Tu b e b
To Circulating
constant
temperature
bath
From Circulating
constant
temperature bath
IN1
OUT2
IN2
OUT1
Fig. 5-4

Fig. 5-8
C
Fig. 5-5
Fig. 5-6
Fig. 5-7
A
B
16
Reference temperature of circulating
constant temperature bath
When the circulating constant temperature bath is used, there is a difference in
temperature indication between the circulating constant temperature bath and the
refractometer. This is a usual phenomenon and comes from the ambient temperature
that affects not only the temperature of water flowing from the bath to the refractometer
but also that of the refractometer itself. Therefore, the temperature of the prism is
balanced with that of the water in the bath at a degree slightly higher than the water in
the bath. Check the difference in temperature between the two and adjust the setting
temperature of the circulating constant temperature bath so that the refractometer is
constantly kept at desired temperature.
5. Preparation for measurement
մ
մ
After tightening the tie band, cut off the
belt tip at C (Figure 5-8).
d)-4
Use of tie band (Figure.5-5).
d)
Fasten each tube with the tie band
according to the following procedure.
Insert an end of tube onto the nozzle so
that the tube fits tightly on the nozzle.
d)-1
To fasten the tube with the tie band,
insert the tip of the tie band into the slot
(Figure 5-6).
d)-2
While holding down the tie band at part
A, pull the tip (B) of the tie band to
tighten (Figure 5-7).
d)-3
The tie band that were tightened
once cannnot be reused.
For removing the tie band from
the tube, cut it.
For fastening the tube with a tie
band again, use a new tie band.
Tie bands can be ordered through
your ATAG O Distributor (refer to
page 43).

6. Power-on
1. Things to be checked before turning on the power.
The brightness of the illuminator lamps
in the refraction field and the scale field
can be adjusted using the brightness
adjustment switch on the upper surface
of the digital thermometer (refer to
page12).
17
Be sure to use the power cable accompanying the main unit.
Do not plug the power cable into any electrical outlet other than AC100 to 240V.
Do not use a power cable that is cut, damaged or processed.
ۍ
ۍ
ۍ
Make sure the power cable is plugged
into the digital thermometer.
a)
Make sure the illuminator lamp cable is
connected properly into the main unit of
the refractometer and the digital
thermometer.
b)
Plug the AC power cable into an indoor AC100 to 240V power outlet. At this time, be sure
to connect the ground pin.
ۍ
When using a circulating constant
temperature bath, make sure it is
connected.
c)
2. Power on
Plug the power cable of the digital
thermometer in an AC100 to 240V
electrical outlet and ensure that the
ground pin is connected as well.
a)
Tu r n on the power switch of the digital
thermometer. The current temperature of
the Abbe refractometer's prism will be
displayed on the digital thermometer.
b)
The sample illuminator lamp and the scale
field illuminator lamp of the Abbe
refractometer will light up.
c)
Contact the dealer or our distributor when the refractometer fails to function properly during
measurement or check up. In such a case, turn off the power switch immediately, and then
unplug the power cable.
CAUTION
WARNING

18
7. Calibration (Scale adjustment)
CAUTION
Calibration with test piece
When measuring solid sample in main, calibrate the scale in this method.
There are two different methods for calibrating the refractometer scale as
mentioned below.
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Don't wet the refractometer except the prism surface with water or sample liquid
unreasonably. If the refractometer gets wet excessively, it may cause malfunction
and breakdown of the refractometer.
Don't tap or pick at the prism surface with a metal spoon, tweezers, etc. because
the prism surface is made of optical glass.
If the prism surface is scratched, the refractometer may fall in measurement.
Method 
Calibration with distilled water
When measuring liquid sample in main, calibrate the scale in this method.
Tu r n the prism open/shut handle to open
the secondary prism (Fig.7-1). After wiping
down the main and secondary prism
surface, drip a small amount of distilled
water on it (Fig. 7-2). Gently close the
secondary prism .
a)
(1) Calibration with distilled water
Connect the refractometer with the
circulating constant temperature bath, and
set the measurement temperature
(temperature indication of the digital
thermometer) to 20Υ.
While observing through the eyepiece,
turn the measurement knob to get the
Refractive Index scale to indicate
approximately 1.3330 and the Brix
percent scale to indicate approximately
0.0% (the upper scale is for reading
Refractive Index while the lower scale is
for Brix percent). When the temperature is
other than 20Υ, the scale must read the
Refractive Index at the actual temperature
and Brix 0.0%.
b)
Fig. 7-1
Fig. 7-2

19
7. Calibration (Scale adjustment)
Seeing the field of refraction view, the
colored boundary line is observed near
the intersection of the cross hairs. Turn
the color compensator knob to
achromatize the boundary line, and stop
turning when the boundary line becomes
neither reddish nor bluish. Since reddish
edge appears just above the boundary
line while bluish edge appears just below
it, the midpoint where neither reddish
edge nor bluish edge appears indicates
that the color is completely compensated.
c) Tu r n the measurement knob again so
that the scale reads 1.3330 (When the
temperature is other than 20Υ, the scale
must read the Refractive Index at the
actual temperature) and Brix0.0%. Adjust
the calibration screw located in the center
of the calibration section with the special
screwdriver supplied as an accessory so
that the boundary line appearing in the
field of refraction meets the intersection
of the cross hairs (Fig. 7-6).
d)
Note:When the measurement temperature is other than 20Υ, adjust the scale indication
to correspond to the Refractive Index at the actual measurement temperature
referring to the following table.
Relation between temperature and Refractive Index (nD)
Te m perature Te m peratureRefractive Index Refractive Index
Υ Υ
nD nD
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
1.33369
1.33364
1.33358
1.33352
1.33346
1.33339
1.33331
1.33324
1.33316
1.33307
1.33299
1.33290
1.33280
1.33271
1.33261
1.33250
1.33240
1.33229
1.33217
1.33206
1.33194
1.33182
1.33170
1.33157
1.33144
1.33131
1.33117
1.33104
1.33090
1.33075
1.33061