Honeywell UDA2182 manual PH/ORP and Conductivity Overview, PH/ORP Calibration

Input Calibration

8.3 pH/ORP and Conductivity Overview

pH/ORP Calibration

Calibration of pH or ORP measuring instruments is necessary because similar electrodes may produce slightly different potentials in the same solution, requiring a corrective adjustment at the measuring instrument. Also, electrode outputs change over a period of time, making periodic recalibration necessary for best performance. Determine recalibration intervals based on operating experience.

Conductivity

Each type of cell has an associated cell constant entered during Configuration Setup. (See Section 6.6) This number is part of the cell model number. However, for greater precision, every Honeywell cell is individually tested at the factory, and a calibration factor unique to that cell is determined. The cal factor for a cell can be found on the plastic tag hanging from the cell lead wires. Instructions for entering this cell cal factor are in Section 6.6. The UDA automatically uploads the Cal Factor from Honeywell cells with EEPROM. This value is displayed in the “Setup” menu.

For some conductivity applications even greater accuracy is required. For those applications it is possible to perform a calibration trim procedure. The Analyzer’s reading can be adjusted while the associated cell is measuring a reference solution of known conductivity, as described in Section 8.7. The same procedure can be used to adjust the Analyzer’s reading while the cell is in the process, if a reference instrument is used to determine the conductivity of the process. In this case the process fluid becomes the “reference solution”.

Calibration trim is recommended for acid concentration applications above 5%. Calibration trim can be reset as described in Section 8.7.

For accurate measurement of total dissolved solids (TDS) a conversion factor is entered for each cell as described in Section 6.6.

ATTENTION

Any time a unit reset is performed; the TDS Value will be reset to 1.0. Calibration trim and cal factor will be reset for cells.

138 UDA2182 Universal Dual Analyzer Product Manual January 2009