Aquametrix AM-TBR Turbidimeter User Manual - Manual (Page 22)

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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 AM-TBR
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 AM-TBR displaying 0.12 NTU.
8. Select the desired offset level using the and buttons. Once the desired level has
been set, press the ↵ button to accept it.
9. This completes the offset configuration.
10. 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, Water Analytics recommends indexing the cuvettes.
Standards and standard kits purchased from Water Analytics 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 button. Now
push and release the ↵ then release the button. Factory calibration and factory configuration
have now been restored.
Note: Restoring the factory settings allows the use of the AM-TBR with reduced accuracy. The
original problem still exists and must be determined and corrected before accurate operation of
the AM-TBR will be resumed.