horiba TW-150 Instruction Manual page 48

4 CALIBRATION
Tips for improving calibration accuracy
Adjust the temperature of the calibrating solution to that of the sample water.

Perform span calibration close to the upper limit of the measurement range.

Use span calibration solution whose value stays within the range.
When starting the system or after replacing the sensors, test run the device for more than

two hours before starting calibration.
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