HF scientific MicroTOL Online Turbidimeter - Manual (Page 21)

MICRO TOL (5/10) 15
Rev. 4.8
7. If the option was turned On, the upper row will display the offset required. This will
add or subtract the value of the offset to the measured NTU value. As an example if
the Micro TOL measures the process at 0.16 NTU but the laboratory instrument read
the sample at 0.12 NTU, adding an offset of –0.04 would result in the Micro TOL
displaying 0.12 NTU.
Select the desired offset level using the
t and u
buttons. Once the desired level has
been set, press the
↵ button to accept it.
8. This completes the offset configuration.
9. At this point, the instrument will continue through the configuration (CONFIG) mode
of the instrument or press MODE/EXIT to return to the AUTO mode.
6.1 Indexing Calibration Cuvettes
To achieve the greatest accuracy, and account for normal scratches and aberrations in
cuvette glass when calibrating, HF scientific recommends indexing the cuvettes.
Standards and standard kits purchased from HF scientific are supplied with indexing rings.
The following steps allow repeatable indexing of calibration standards:
1. With the instrument in AUTO mode insert the standard.
2. Slowly rotate the standard, inside the optical well, one complete revolution (360º).
While rotating the standard slowly, observe the measured turbidity and locate the
position of the cuvette having the lowest reading.
3. 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 faces directly forward.
When using the standards in future, always insert the standard so that the pointer of the
indexing ring faces forward. Slowly rotate the standard back and forth about 5
° to find the
lowest point. The standard is now indexed and ready for use.
6.2 Restoring Factory Settings
If the instrument is unable to perform a calibration due to a low lamp output or a
calibration using the wrong standards, the instrument will display CAL on the lower row
of the display and Err on the upper row. The operator has two choices to correct this
problem. If the operator can determine whether a poor calibration or a low lamp caused
the problem, he/she can remedy the problem and recalibrate. If all else fails, the operator
may restore the factory calibration and configuration settings by performing the following
operation. Push and hold the
tbutton. Now push and release the ↵ then release
the
tbutton. Factory calibration and factory configuration have now been restored.
Note: Restoring the factory settings allows the use of the Micro TOL with reduced accuracy.
The original problem still exists and must be determined and corrected before
accurate operation of the Micro TOL will be resumed.