HF scientific MicroTOL Online Turbidimeter old series- 0-1000 NTU - Manual (Page 18)

MICRO TOL (12/04)
Rev. 2.7 12
5.0 Instrument Calibration
The instrument was calibrated and tested prior to leaving the factory. Therefore, it is
possible to use the instrument directly out of the box. Under normal conditions, re-
calibration is recommended at least once every three months
1 . If calibration is not
performed, the instrument will continue to monitor the turbidity of the process water with
a decreased accuracy.
Relay contacts are held at the last valid condition and will not change state while the
instrument is in the calibration and/or in the configuration mode. While in the calibration
mode, the instrument has a time-out feature that automatically returns the system
operation to the AUTO mode after a thirty (30) minute period of inactivity.
5.1 Calibration Standards
If the Micro TOL will be used over the entire range of .02 to 1000 NTU a complete
calibration as described below will be required. If instrument accuracy is only required
below 10 NTU, such as potable water, a calibration may be performed using only a 10
NTU and a 0.02 NTU standard. To calibrate starting at the 10 NTU, press the
tbutton
to bypass the 1000 NTU and proceed to Section 5.2 Calibration Procedures, step 5 . Note
that using the
t and u
buttons you can rotate through the requested standards and get to
the END prompt. Pressing the
↵
button at the END prompt will have the same affect as
pressing the MODE/EXIT button; no calibration change will have been made.
We recommend that you use the following materials during calibration to achieve the
full-scale accuracy stated in this manual:
1. 0.02 NTU Calibration Standard available from HF scientific inc.
2. 10.0 NTU Calibration Standard available from HF scientific, inc.
3. 1000 NTU 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.
,
primary calibration standards (refer to section 10.0 Accessories and Replacement Parts
List) are more stable than Formazin and have a minimum shelf life of 12 months. Prior to
recalibration, review the expiration dates, to ensure that the standards have not expired.
5.2 Calibration Procedures
1. Select the calibration function of the instrument by pressing the MODE/EXIT button
once. The arrow beside CAL will be illuminated on the display. The lower display
shows alternating 1000 (the value of the standard that is requested) and
↵. The upper
display shows the real-time reading to allow the standard to be indexed. Refer to
section 6.1 for information on indexing cuvettes.
1 The EPA recommends that on-line turbidimeters be calibrated with a primary standard at least once every three
months if they are to be used for EPA reporting.