HF scientific 19998 Triple Validation Turbidimeter - 0-100 NTU - Manual (Page 20)

TVT 1 (5/02) 14
Rev. 2.6 (.pdf)
record the turbidity reported by the instrument.
2. Take the grab sample and measure its turbidity using your laboratory turbidimeter
(contact the HF scientific, inc. customer services department for examples of laboratory
turbidimeters).
3. Compare the turbidity reported by the instrument to that obtained in your laboratory. If
the readings are very close, then no offset adjustment or calibration is required and you
may stop the procedure at this step. However, if the readings are substantially different,
you may continue on in this procedure to utilize the offset option to improve the turbidity
reading of the instrument so that it will agree with your laboratory reading between
calibrations.
4. Select the calibration-offset function of the instrument by pressing the MODE button
until the “OFFSET” and “CAL” blocks are illuminated on the display.
5. At this point, the lower row of the display will indicate the operational status of the offset
function (on or off). You may change this status by using the
t and u buttons. Once
you have set the desired operational status of the offset function press the
↵
button to
accept it. If you turned the option off, you will return to the SETUP mode. Press MODE
to return to the automatic measurement mode.
6. If you turned the option on, you will be prompted to enter the laboratory measurement of
the grab sample (LAB).
Select the turbidity level for your grab sample using the
t
and
u
buttons. Once
you have set the desired level, press the
↵
button to accept it.
7. Next, you will be prompted to enter the on-line measurement of the grab sample (OLR).