HF scientific MicroTPW Field Portable Turbidimeters - Manual (Page 13)

MicroTPI & MicroTPW (5/10)
Rev. 1.9
7
4.0 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. However, re-calibration of the
instrument is recommended to help with familiarization and the operation of the
instrument and the calibration procedures. In addition, re-calibration is recommended at
least once every three months.
The instrument requires three (3) standards to be fully calibrated.
During calibration, the instrument performs several system self-diagnostics. As such,
several warning messages may be displayed. If the instrument detects an irregularity
(detectors or lamp) a warning message will be displayed. If this occurs please attempt to
rectify the problem, or contact the authorized technical services department (see section
6.4). In any event, the instrument will continue to read the turbidity with a decreased
accuracy until the error is rectified.
4.1 Calibration Standards
We recommend the following materials during calibration to achieve the accuracy stated
in this manual:
1. 1000 NTU ProCal Calibration Standard available from HF scientific inc.
2. 10.0 NTU ProCal Calibration Standard available from HF scientific inc.
3. 0.02 NTU ProCal Calibration Standard available from HF scientific inc.
It is well known that diluted Formazin is unstable. If Formazin is used to calibrate the
instrument, ensure that a fresh stock suspension of Formazin is used to achieve the
accuracy quoted for the instrument. A Formazin Stock Solution Kit is available.
ProCal
calibration standards are more stable than Formazin and have a limited shelf life of 1
year. If
ProCal
calibration standards are used to calibrate the instrument, review the
expiration date to ensure that the standards have not expired. ProCal calibration standards
are a US EPA approved alternative standard to Formazin.
4.2 Indexing the Calibration Standards
The United States Environmental Protection Agency (US EPA) recommends that
cuvettes used for instrument calibration or sample measurement be indexed. To comply
with this recommendation, each calibration standard is supplied with an indexing ring
and each instrument has a reference point for quick and repeatable indexing of the
calibration standard. To index a calibration standard perform the following steps:
1. While holding down the
↵
button, slowly rotate the calibration standard one
complete revolution (360°) pausing between increments to allow the display to
update.
2. While rotating the standard, observe the turbidity reading and locate the cuvette
position with the lowest turbidity reading.
3. With the calibration standard positioned at the location having the lowest turbidity
reading, install the Indexing Ring over the black light shield on the standard so that
the pointer of the Ring aligns with the reference arrow on the instrument.