EUTECH INSTRUMENTS TURBIDIMETER TN-100 WATERPROOF PORTABLE METER Instrukcja Obsługi Pobierz pdf (Strona 25)

Instruction Manual TN-100/ T-100

9 ADDENDUM 2: GUIDE TO GOOD MEASUREMENT

TECHNIQUE

Turbidity is a very complex analytical measurement which can be affected

by many factors. Some are inherent in the instrument’s design such as

angle of detection, light beam aperture, incident beam wavelength and

colour sensitivity of the photocell.

However, there are other factors such as stray light, air bubbles and care

of vial, which can be prevented through proper care of equipment and

accessories, and in the operating procedure for measurement. Here are

some points you may want to note:

9.1

Maintain sample vials in good condition

Sample vials must be meticulously clean and free from significant

scratches. It should be treated on the outside with a thin coat of silicone

oil. This is to mask minor imperfections and scratches that may contribute

to stray light. Sample vials should be handled only by the top to avoid dirt

accumulation (or deposits) and fingerprints that might interfere with the

light path.

More information is found in Section 5.1 - Vials – Handling, Cleaning and

Care on page 16.

9.2

Match Sample Vials

Best accuracy and repeatability of turbidity measurement are achieved

using a single, indexed vial. However, for more convenience, different

vials can be used for measurement provided their readings with the same

solution are matched. That is, the meter gives identical readings or within

the specified repeatability and accuracy of the meter.

Select a few vials. After the sample vials are cleaned, fill them with ultra-

low turbidity water. Allow the sample vials to stand and for air bubbles to

rise. Polish sample vials with silicone oil and take turbidity measurement at

several points while rotating it in the sample well. Find the position where

turbidity reading is the lowest and index it for each vial. Whenever these

sample vials are used, use the indexed mark to position each vial into the

sample well. Choose those vials that match the readings.

NOTE:

Not all vials can be matched because of some

manufacturing variations.

9.3 Degassing

Air or other trapped gases should be removed before measurement.

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