Extech RF40 User guide

User's Guide

Battery/Coolant Refractometer with ATC

Model RF40-C

Introduction

Congratulations on the purchase of your RF40-C Battery/Coolant
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.

Description

1. Eyepiece

2. Mirror tube

3. Adjustment Screw

4. Cover plate

5. Prism

Field of View

Operation

The instrument measures the refractive index of the sample.

1. Zero Adjustment

Place one or two drops of distilled water on the prism. Close the cover
plate and rotate the adjusting screw so that the light/dark boundary lines
up with the “waterline”. Once the zero adjustment has been completed,
clean the prism with soft cloth

2. Sample Preparation and Reading

To take a sample reading, simply
place a few drops of a sample liquid
on the measurement prism at the
end of the instrument. Lower the
cover plate onto the sample and
prism. Open the prism cover and
place 2 or 3 drops on the prism.
Close the cover so the liquid spreads
across the entire surface of the prism
without air bubbles or dry spots.
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 freezing point of the liquid or the state of the battery liquid
is determined by the intersection of the boundary of the light and dark
fields (known as the shadowline) on the printed scale. 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 shadowline. 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 one of the single most important factors influencing
accurate refractometer readings and is one of the largest sources of
error in measurement. Temperature compensation relieves the user of
the responsibility to measure temperature and apply a correction factor
when taking readings. This refractometer makes this correction
automatically. When ambient temperature varies from 20°C (68°F),
readings are automatically adjusted to compensate for temperature
variance between 10°C to 30°C (50°F to 86°F).

Specifications

Range -51 to 0°C (-60 to 32°F) for propylene and
ethylene glycol freeze point

1.10 to 1.40 specific gravity of battery acid
Resolution 1°C/2°F glycol freeze point

0.01 specific gravity of battery acid
Dimensions 6.5x1.5x1.5" (165x38x38mm)
Weight 7.0 oz. (200g)

All rights reserved including the right of reproduction in whole or in part in any form.

Copyright © 2006 Extech Instruments Corporation.

Version 1.0 March 2006

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