Aquametrix AM-TBR Turbidimeter User Manual - Manual (Page 18)

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5. 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 .
Relay contacts will change to the alarm 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 fifteen (15) minute period
of inactivity.
5.1. Calibration Standards
If the AM-TBR 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 button to bypass the 1000 NTU and proceed to
Section 5.2, step 5.
We recommend that the following materials be used during calibration to achieve the full-scale
accuracy stated in this manual:
1. 0.02 NTU TBR-Cal Calibration Standard available from Water Analytics
2. 10.0 NTU TBR-Cal Calibration Standard available from Water Analytics
3. 1000 NTU TBR-Cal Calibration Standard available from Water Analytics
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 Water Analytics (Catalog No.
50040). The Water Analytics TBR-Cal, primary calibration standards (refer to section ) 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 range of Models 20055 & 20056 is .02 to 100 NTU. For calibrating these models
replace the 1000 NTU standard with a 100 NTU standard.
5.2. Calibration Procedures
1. Select the calibration function of the instrument by pressing the MODE/EXIT button once.
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.