HF scientific Micro100 Laboratory Turbidimeter - Manual (Page 12)

Micro 100 (5/10) Page 6
Rev. 3.3
If the Micro 100 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
ubutton to bypass the 1000 NTU and proceed to Section 5.2
Calibration Procedures, step 4.
We recommend that the following materials be used during calibration to achieve the full-scale accuracy
stated in this manual:
1. 0.02
NTU ProCal Calibration Standard available from HF scientific.
2. 10.0 NTU ProCal Calibration Standard available from HF scientific.
3. 1000 NTU ProCal Calibration Standard available from HF scientific.
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 from HF scientific (Catalog No. 50040). The
HF scientific
ProCal , 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.
NOTE: The MICRO 100 must be re-calibrated after lamp replacement.
5.1
Indexing the Calibration Standard(s)
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
HF scientific calibration standard is supplied with an indexing ring for quick and repeatable indexing of
the calibration standards.
To index a calibration standard perform the following steps:
1. Slowly rotate the calibration standard one complete revolution (360°).
2. While rotating the standard, observe the Micro 100 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 faces
forward, toward the operator.
When using the standards in the future, always insert the standard so that the pointer of the indexing ring
faces forward. Slowly rotate the standard, back and forth about 5° to find the lowest point. The standard
is now indexed and read for use.
5.2 Calibration
Procedure
Even though it is possible to calibrate the MICRO 100 using any sequence of the prescribed calibration
standards, to achieve the stated accuracy you must use the procedure below to calibrate the instrument.
1. Press the
key. Once this key is pushed the “Ident” block and the “Cal” block will
illuminate on the display.