Xylem TB500 ONLINE TURBIDITY ANALYZERS - Manual (Page 15)

TB500 (2/07)
Rev. 1.0 11
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
.
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 fifteen (15) minute period of inactivity.
5.1 Calibration Standards
If the TB500 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 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 Calibration Standard available from Global Water
2. 10.0 NTU Calibration Standard available from Global Water
3. 1000 NTU Calibration Standard available from Global Water.
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
Global Water (Model # TB500-FOR). The primary calibration standards offered from
Global Water (refer to section 11.0 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.
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.