Operation
Turbimax CUE25 / CUE26
12
Hauser
4.4
Instrument calibration
The instrument was calibrated and tested prior to leaving the factory. Therefore, it is possible to use
it directly out of the box. However, recalibration of the instrument is recommended to help with
familiarization and the operation of the instrument and the calibration procedures. In addition,
recalibration is recommended at least once every three months
2)
.
The instrument requires three standards to be fully calibrated.
4.4.1
Calibration standards
We recommend that the following standards be used during calibration to achieve the full-scale
accuracy stated in this manual:
• 0.02 NTU calibration standard
• 10.0 NTU calibration standard
• 1000 NTU calibration standard
These primary calibration standards are more stable than Formazin and have a minimum shelf life
of 12 months. Prior to recalibration, review the expiration dates to ensure that the standards have
not expired.
If you use Formazin to calibrate the instrument, make sure that a fresh stock suspension of Formazin
is used to achieve the accuracy quoted for the instrument.
!
Note!
The 10.0 NTU standard is only guaranteed to hold its value for 12 months when stored in the plastic
bottle. After pouring it into the glass cuvette, it should be used immediately for calibration and then
be disposed of. If the 10.0 NTU standard is stored in the glass cuvette for extended periods of time,
it should be used as a reference standard only.
4.4.2
Indexing calibration cuvettes
To achieve greatest accuracy and account for normal scratches and aberrations in cuvette glass
when calibrating, we recommend indexing the cuvettes.
Standards and standard kits purchased from Hauser are supplied with indexing rings.
The following steps allow repeatable indexing of calibration standards:
1.
Press and hold the
F
key.
2.
Slowly rotate the standard inside the optical well, one complete revolution (360°) pausing
between the increments to allow the display to update.
3.
While rotating the standard slowly, observe the measured turbidity and locate the postion of
the cuvette having the lowest reading.
4.
With the calibration standard positioned at the location having the lowest turbidity reading,
install the indexing ring over the cap on the standard so that the pointer of the indexing ring
aligns with the arrow on the instrument.
When using the standards in future, always insert the standard so that the pointer of the indexing
ring aligns with the arrow. Slowly rotate the standard back and forth about 5° to find the lowest
point. The standard is then indexed and ready for use.
2)
The EPA recommends that on-line turbidimeters be calibrated with a primary standard at least once every three months if they are to be used for EPA reporting.
