YSI 6000UPG - Manual (Page 62)

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as instructed, press any key to return to the Calibrate menu. This procedure should only be used to
update a previous 2-point or 3-point calibration.
Select the 2-point option to calibrate the turbidity probe using only two calibration standards. One
of the standards must be clear water (0 NTU) and the other should be in the range of known
turbibity for the water to be monitored. For example, if the water to be evaluated is known to be
low in turbidity, an appropriate choice of standards might be 0 and 10 NTU. If the water to be
evaluated is known to be very cloudy, an appropriate choice of standards might be 0 and 100 NTU.
To begin the calibration, immerse the sonde in the 0 NTU standard, as instructed, and press Enter.
It is mandatory that the 0 NTU standard be calibrated first. The screen will display real-time
readings which will allow you to determine when the readings have stabilized. Pressing Enter will
confirm the first calibration. Following the instructions on the screen, place the sonde in the second
turbidity standard, input the correct turbidity value in NTU, press Enter, and view the stabilization
of the values on the screen in real-time. After the readings have stabilized, press Enter to confirm
the calibration. Then, as instructed, press any key to return to the Calibrate menu.
Select the 3-point option for maximum accuracy over the entire range of 0 to 1000 NTU. As for
the 2-point procedure, one of the standards must by 0 NTU. Because of the linearity characteristics
of the sensors, we recommend that the other two standards have turbidity values of 10 and 100
NTU. However, the user can select any values which are deemed appropriate. The procedure for
this calibration is the same as for a 2-point calibration, but the software will prompt you to place the
sonde in the additional solution to complete the 3-point procedure.
For all turbidity calibration procedures, be certain be certain that the standard and sensor are
thermally equilibrated prior to proceeding with the calibration. Remember that all multipoint
turbidity calibrations must be done in order from 0 NTU and up. In this example, do 0 NTU, then
10 NTU, and finally 100 NTU.