User`s guide

Appendix E – Measuring pH with UMC800 Controller and Durafet II Cap Adapter
Zero and Slope Standardization Operations
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Zero and Slope Standardization Operations
The standardization process requires the Track and Hold blocks to be activated for a short period while the
electrode is placed in a buffer solution of known pH. This is a two step operation where the zero and
temperature track and holds are activated for the zero buffer, then the slope track and hold is activated for
the slope buffer. To accomplish this, the block configuration in Figure 77 is used.
This configuration allows a digital variable to be turned ON for a specified time period (3 seconds), and
then uses a write variable block to reset the digital variable to OFF. Two of these sequences are used, one
for the zero standardization time, the other for the slope standardization time. ON/OFF labels for the
ZERO variable = Z CAL for ON and READY for OFF. The ON/OFF labels for the SLOPE variable = S
CAL for ON and READY for OFF.
Figure 77 Zero and slope standardization functions