Hanna Instruments HI 93414 - Manual (Page 15)

15
CUVETTE OILING (TURBIDITY only)
Warning: For colorimetric measurements the cuvette should be completely free of any trace of oil.
Do not use the oiling procedure for colorimetric measurements.
To hide minor imperfections and scratches, the cuvettes should be oiled outside with the supplied
silicone oil. This is very important, especially for low turbidity samples (< 1 NTU), otherwise
scratches can contribute and alter turbidity readings.
The silicone oil has the same refractive index as the glass and will not alter the turbidity readings.
It is important to apply only a thin layer of silicone oil.
Warning: Do not apply silicone oil in excess because it may retain dirt or contaminate the cuvette
holder of the instrument, altering the turbidity readings.
It is very important to apply the silicone oil on a clean, dry cuvette. Apply a few drops of oil and wipe
the cuvette thoroughly with a lint-free cloth. Wipe off the excess oil till you obtain a thin, uniform
layer. If the procedure is correctly followed, the cuvette should appear nearly dry with no visible oil.
Note: The supplied cloth for oiling should be stored together with the silicone oil bottle and
cuvettes, taking care to avoid contamination with dirt. After a few oiling procedures, the cloth
will contain enough oil to wipe the bottle with it without adding more oil. From time to time
add some drops of oil on the cuvette to provide the necessary oil quantity in the cloth.
INDEXING A CUVETTE
It is very important for low turbidity readings to always insert the cuvette into the instrument in
the same position.
All cuvettes are factory indexed. This index can be used to put the cuvette with the factory mark on
the cuvette aligned with the sign on the instrument top.
To further reduce the effect of glass imperfections, the cuvette can be indexed and use this new index
as the position mark.
For indexing one cuvette or matching multiple cuvettes, the continuous reading mode is suggested.
In this mode, if
READ/TIMER is kept pressed, multiple successive readings are taken without
turning off the lamp. After first reading is displayed, it is possible to open the cuvette lid and rotate
the cuvette without generating an error condition. The turbidity is immediately displayed, reducing
considerably the measurement time. The lamp of the instrument will turn off only when
READ/
TIMER is released.
Note: The instrument can not perform continuous readings if the average mode is on.