YSI 556 MPS - Manual (Page 52)

Section 6 Calibrate
YSI 556 MPS YSI Incorporated Page 46
Figure 6.12 pH Calibration Screen
¾ Select the 1-point option only if you are adjusting a previous
calibration. If a 2-point or 3-point calibration has been
performed previously, you can adjust the calibration by carrying
out a one point calibration. The procedure for this calibration is
the same as for a 2-point calibration, but the software will
prompt you to select only one pH buffer.
¾ Select the 2-point option to calibrate the pH sensor using only
two calibration standards. Use this option if the media being
monitored is known to be either basic or acidic. For example, if
the pH of a pond is known to vary between 5.5 and 7, a two-
point calibration with pH 7 and pH 4 buffers is sufficient. A
three point calibration with an additional pH 10 buffer will not
increase the accuracy of this measurement since the pH is not
within this higher range.
¾ Select the 3-point option to calibrate the pH sensor using three
calibration solutions. In this procedure, the pH sensor is
calibrated with a pH 7 buffer and two additional buffers. The 3-
point calibration method assures maximum accuracy when the
pH of the media to be monitored cannot be anticipated. The
procedure for this calibration is the same as for a 2-point
calibration, but the software will prompt you to select a third pH
buffer.
4. Use the arrow keys to highlight the 2-point selection.