User's Guide
Portable Salinity Refractometer with ATC
Model RF20
Introduction
Congratulations on your purchase of the Extech RF20 Handheld Salinity Refractometer
with Automatic Temperature Compensation. This precision optical instrument should be
handled gently; avoid touching the optical surface. Careful use of this instrument will
provide years of reliable service.
Test Equipment Depot, 99 Washington Street, Melrose, MA 02176
781.665.1400 | 800.517.8431 | Fax: 781.665.0780
99 Washington Street
Melrose, MA 02176
Phone 781-665-1400
Toll Free 1-800-517-8431
Visit us at www.TestEquipmentDepot.com
Back to the Extech RF20 Product Info Page
Specifications
Scale Range Resolution
Parts Per Thousand 0 to 100 0/00 1
Specific Gravity 1.000 to 1.070 d20/
Dimensions 7.6 x 1.5 x 1.5" (194 x 38 x 38mm)
Weight Approx. 8.0 oz. (227g)
0.001 d
20
0
/00
20
/
Description
1. Prism
2. Cover Plate
3. Adjustment Screw
4. Mirror Tube
5. Eyepiece
1 2 3 4 5
20
2
RF20 Version 1.1 September 2003
Operation
The instrument measures the refractive index of the sample and displays the result in parts
per thousand (
1. Zero Adjustment
Put distilled water on the prism; enough to cover the entire prism. Close the cover plate
and rotate the adjusting screw so that the light/dark boundary line (known as the
shadow-line) evens up with the zero line. After the zero adjustment, clean the prism with
soft cloth.
2. Sample Preparation and Reading
To take a reading, place a few drops of a sample liquid on the measurement prism.
Ensure that enough solution is added to the prism in order to cover the entire prism.
Close the prism so that the liquid spreads across the entire surface of the prism without
air bubbles or dry spots (see diagrams below). Allow the sample to remain on the prism
for approximately 30 seconds.
While holding the instrument under a light
source, look through the eyepiece. The
salinity concentration is determined by the
intersection of the boundary of the light
and dark fields (known as the shadowline) on the printed scale. The left side of
the scale indicates the specific gravity and
the right side parts per thousand. If the
scale appears out of focus, the eyepiece
may be adjusted by rotating the knurled
portion. The instrument also features an
eye guard to prevent stray light from
entering the eyepiece and causing
reflections.
It may be necessary to adjust the position of the light source to maximize the contrast of
the shadow-line. Under normal conditions, optimal contrast is obtained by holding the
instrument underneath and perpendicular to a light source.
Once a reading has been taken, wipe dry with a clean cloth (do not wash or rinse) and
place the instrument in the supplied plastic case. Store the instrument in a safe, dry
environment.
Temperature is the single most important factor influencing refractometer readings and
is one of the largest sources of measurement error. However, this device incorporates
automatic temperature compensation and the concern for temperature fluctuations in
sample liquids is alleviated. When ambient temperature varies from 68°F (20°C),
readings are automatically adjusted to compensate for temperature variance between
50°F to 86°F (10°C to 30°C).
0
/00 ) and specific gravity (d 20/20).
Bad Bad Good
Test Equipment Depot, 99 Washington Street, Melrose, MA 02176
781.665.1400 | 800.517.8431 | Fax: 781.665.0780
3
RF20 Version 1.1 September 2003
Loading...