HF scientific AccUView Wastewater UV %Transmission Monitor - Manual (Page 21)

6.0 Instrument Offset
In certain instances, it may be desirable to use an offset factor to calibrate the instrument
rather than performing a physical calibration of the instrument (as described in section
5.1). This procedure is not recommended in lieu of regular instrument calibration but it
can be used in situations where the number of instruments used makes regular calibration
prohibitive. This calibration technique will make the instrument accurate
only at levels
near the measured value of the grab sample and
not in the full range of the instrument.
Note that the
OFFSET icon will be illuminated whenever an offset used. The maximum
offset is ± 1.0 %T If instrument variation is greater than 1 %T a full calibration is
recommended.
The procedures are as follows:
1. Collect a grab sample of the process water that is being monitored by the instrument
and record the reading reported by the AccUView Wastewater.
2. Take the grab sample and measure its value using a laboratory photometer (contact the
HF scientific customer services department for examples of laboratory photometers).
3. Compare the reading reported by the AccUView Wastewater to that obtained in the
laboratory. If the readings are very close, then no offset adjustment or calibration is
required and the procedure may be stopped at this step. However, if the readings are
substantially different (but less that 1 %T) continue on in this procedure to utilize the
offset option to improve the reading of the AccUView Wastewater so that it will agree
with the laboratory reading between calibrations.
4. Select the offset function of the instrument by pressing the
MODE/EXIT button until
the arrow beside
CONFIG is illuminated on the display. Refer to the following screen.
5. Push the
↵
button until
OFST is displayed on the lower row.
6. At this point, the lower row of the display will indicate the operational status of the
offset function ( On or OFF). Change this status by using the t and u
buttons.
Once the desired operational status of the offset function has been set, press the
↵
button to accept it. If the option was turned off, return to
pre-AUTO mode by
pressing
MODE/EXIT. Then press the ↵ button to return to normal operation.
7. If the option was turned
On, the upper row will display the offset required. This will
AccUView Wastewater (1/09) 15
Rev. 2.9