HF scientific 19998 Triple Validation Turbidimeter - 0-100 NTU - Manual (Page 16)

TVT 1 (5/02) 10
Rev. 2.6 (.pdf)
instrument and the calibration procedures. Under normal conditions, re-calibration is
recommended at least once every three months
1 .
During calibration, the instrument performs several system self-diagnostics. As such,
several warning messages may be displayed. If the instrument detects an irregularity
with the instrument (detectors or lamp) a warning message will be displayed on the lower
row of the display on exit from the calibration mode. If this occurs please attempt to
rectify the warning message yourself, or contact the HF scientific, inc technical services
department. In any event, the instrument will continue to monitor the turbidity of the
process water with a decreased accuracy until the error is rectified.
In addition, if the instrument remains in the calibration mode for longer than 5 minutes
with no activity, it will time out and return to the automatic measuring mode.
5.1 Calibration Standards
We recommend that you use the following materials during calibration to achieve the
accuracy stated in this manual:
1. De-ionized water filtered through a 0.02 µm filter
2. 10.0 NTU Formazin primary standard, or 10.0 NTU pour through Calibration
Standard available from HF scientific, inc.
3. 100 NTU Formazin primary standard, or 100 NTU pour through Calibration Standard
available from HF scientific, inc.
It is well known that diluted Formazin is unstable. If you choose to use Formazin to
calibrate the instrument, ensure that you are using a fresh stock suspension of Formazin
to achieve the accuracy quoted for the instrument. A Formazin Stock Solution Kit is
available from HF scientific, inc. (Catalog No. 50040). The HF scientific, inc. calibration
standards (Catalog No. 19996) are more stable than Formazin and have a shelf life of 1
year. Prior to re-calibration, review the expiration date to ensure that the standards have
not expired.
5.2 Calibration Procedures
All TVT’s are shipped with a range of 0-10. A range of 0-100 NTU may be selected by
adding the included shorting strap (See section 7). If you did not request a measurement
range then you have a 0-10 NTU instrument. If you selected a range of 0-100 in section
7, then you should complete steps 7-10 using a 100 NTU standard first and then repeat
the steps with a 10 NTU standard.
1. Select the calibration function of the instrument by pressing the MODE button once. The
“CAL” block will be illuminated on the display with the turbidity value of 10.0 (or 100 for
0-100 NTU range) NTU displayed on the LCD. This is the first standard that should be used
in calibration.
1 The EPA recommends that on-line turbidimeters be calibrated with the primary standard (Formazin) at least once
every three months if they are to be used for EPA reporting.