Auto Cal Value

What happens when “Auto Cal” is performed after manual two point calibration

Recommendation

pH

4.01 pH

Up to 2 point calibration is possible with the U-20.

When performed manual calibration with pH4 (span) and pH7 (zero), performing “Auto Cal” will simply “update” pH4 calibration.

When performed manual calibration with pH9 (span) and pH7 (zero), “Auto Cal” will delete pH9 calibration and over write with pH4.

In both cases, manual calibration for pH7 remains.

When you know the sample is at Alkaline side, do not perform Auto Cal after your pH7+pH9 manual calibration.

Conductivity

0.449 S/m

The mid-range span value of manual conductivity calibration is 0.667 S/m. Auto-cal will over write this mid-range span value with 0.449 S/m. It will also automatically calculate the deviation against the previous calibration from the mid-range and adjust the span calibration of lowest (71.8 mS/m) and highest (5.87 S/m) ranges.

Manual calibration for zero will remain.

Although “Auto Cal” will reflect its calibration with mid-range value to lowest and highest range, user have to understand that a better accuracy is obtained when calibration is performed with the actual standard solution than “calculated” value.

Turbidity

0 NTU

It will over write the zero calibration from the manual calibration. Span calibration will remain.

For both manual and “Auto-Cal2, make sure the container for the standards is clean and have no contamination. When the standard is contaminated, it will affect the lower turbidity value.

DO

8.52 mg/L

It will over write the span calibration from the manual calibration, from 8.11 to 8.52. Zero calibration remains.

Depth

0 m

It will over write the 0m.