8
equilibrate, and press CALIBRATE (screen
14). A successful calibration will bring up
screen 15. Repeat the procedure for the
rest of your calibration standards.
NOTE: The calibration standards must be
sequential.
In other words, the index of water is <std#1
<std#2<std#3<std#4. TheAR6 will not sort
the standards if you scramble their order,
and the accuracy of your readings will
diminish.
5.1 Preparing the Prism Surface for Samples
Because a refractometer is an optical instrument, it is
critical to thoroughly clean the sample measurement area.
Any residue could result in erroneous
readings or error messages.
Clean the prism surface and sample well
with diluted soapy water or alcohol followed
by a distilled water rinse before applying a
sample. Wipe clean with a soft cloth.
5.2 Applying the Sample, Taking
Readings, and Shadowline Dis-
play
Place the sample on the prism surface using a pipet or
applicator. Make sure the entire prism surface is covered
(Figure 4). Optimum readings are obtained
if enough sample is placed in the well to
cover a millimeter or two of the walls of the
sample well.
Close the cover and press the READ key. The
REICHERT AR6 will display the reading in
the selected mode.
If you change modes before taking a new reading, the
instrument will use data from the current reading to
produce a new display in the newly selected mode.
For example, if you want a reading in nD, fol-lowed by %
Solids using one measurement of the sample, operate
the REICHERT AR6 in the nD mode. Then
press the MODE key until % Solids or %
Solids-TC registers on the display. A %
Solids reading will automatically be
displayed. If the READ key is pressed, the
AR6 will take an entirely new measure-
ment.
In addition, the instrument now has the ability to
graphically display the shadowline via the Linear Scanned
Array output. This allows the user to “see what the
refractometer sees”. This feature may be operated after
any reading by pressing the “CALIBRATE” and “MODE”
keys simultaneously. The refractometer will then generate
and display a graph of the Linear Scanned Array Output.
See example below.
Two lines will appear. The rainbow shaped
line is the Reference Scan. The line which
begins near the bottom of the screen and
moves upward to intersect the Reference
Scan is the Sample Reference Scan. Also
shown will be the “CCN”. This is the
Crossing Cell Number which is the exact
cell on the array which the edge of the
shadowline falls on. At this point, a box will
be displayed. This box may be repositioned
anywhere on the screen. Pressing “SET
UP” will zoom in on this boxed area.
Pressing “SET UP” again will return to the
full graph view. The X and Y values are also
displayed. These are simply the location of
the box on the screen. The line for the
reference scan may be toggled on and off
by pressing “READ” and “INITIATE”
simultaneously in the full graph display. To
exit the shadowline display, press “CALI-
BRATE” and “MODE” simultaneously.
6.0 DIAGNOSTICS
The following screens describe potential errors that can
occur when operating the AR60O:
“High Sample” screen - The sample has a refractive
index exceeding the 1.52000 operating range limit (see
Screen 16).
“Low Sample” screen - The sample has a
refractive index below the 1.32000
operating range limit (see Screen 18).
“Water Calibration” screen - This screen will be displayed
when the READ key is pressed before a water
calibration. Clean the prism, calibrate with water and
reread the sample (see Screen 19).
“Lamp is not Aligned” screen - This screen may appear if
a sample has been left on the prism. Thoroughly clean
and dry the prism surface. If the message persists, the
lamp may need re-alignment. Note the direction to move
the lamp and re-center the lamp. Alignment is done with
the instrument running. Use a metal screwdriver to move
the lamp due to it’s high temperature. Exercise care to
avoid breaking the lamp. Wear eye protection in case the
lamp shatters. Follow the on screen instruction to initiate
and recalibrate the AR6 (see Screen 20).
“Replace Lamp” screen - The lamp is burned out Replace
the lamp following instructions in section
11.0 LAMP REPLACEMENT (see screen
21).
“Could Not Take Proper Reading” screen - This screen
will be displayed if the lamp intensity has changed since
the initialization procedure. This can be caused by normal
aging of the lamp or large line voltage fluctuations. Check
to be sure the lamp is illuminated, turn the AR60O off
and back on, follow the on screen instruction to initiate
and calibrate instrument (see Screen 22). If the condition
persists change the lamp. If it continues
with a new lamp a line voltage conditioner
may be required. Alternately, the AR60O
could be plugged into a separate line
source, preferably a source without
electrical appliances which have large
current draws (e.g.: motors, compressors,
heaters, etc.).
7.0 CHANNELS
Channel one (1) on the REICHERT AR6 is
pre-programmed at the factory with the %
Sucrose or «Brix» scale per the
International Commission for Uniform
Methods of Sugar Analysis (ICUMSA).
Up to 14 additional custom channels may be
programmed using your own refractive index/
temperature/% Solids data. Access to the channels is
from the SET UP screen. Custom channels may also
include definitions for units of measure such as specific
gravity, % protein, g/ml, etc. The unit of measure labels
are completely definable and up to 20 characters can be
used. Results may be displayed in as many decimal
places as desired.
To learn more about custom channel progamming,
request «Custom Channel Generation for the Automatic
Refractometer Line» from a Reichert representative. Be
sure to inform the representative that you are using
software version 12.6.
8.0 AUTOMATIC TEMPERATURE
COMPENSATION
Automatic Temperature Compensation corrects readings
taken over a range of temperatures (e.g.:
10°C – 40°C in channel 1) to a reference
temperature reading (usually 20°C). This
can be used in lieu of controlling the
temperature of the prism and sample with
an external water bath. Temperature
correction or control is necessary because
refractive index varies inversely with
temperature. A typical temperature
coefficient for an aqueous solution is -
0.00021°C. For an organic liquid it is
typically -0.0004/°C.
However, it is always necessary to allow your sample
temperature to equilibrate so that the AR6
can properly correct for temperature.
The automatic temperature compensation modes in
channel 1 are based on the temperature coefficients
(n
D
1°C) of sucrose per the ICUMSA scales. When taking
readings in the nD–TC (refractive index – Temperature
Compensated) mode these coefficients
may not be valid depending on the solution.
