ORP measurement is often used in an addition to pH measurement to get the best performance from your water treatment system.

For process control, it’s important to make the measured ORP agree with the ORP of a standard solution. During ORP standardization, the measured ORP is made equal to the ORP of a standard solution at a single point.  Even though it’s often referred to as “calibration”, it’s actually a”standardization”.

ORP is the measurement of the strength of the reaction taking place.  Since ORP is the measurement of the solution’s total millivolt potential, it’s non-specific. It’s like a voltmeter for measuring liquids.  The zero point is known. There’s no control variable to vary, as in the case of pH or Conductivity. We use a solution of chemicals that give a known potential that we can measure in mV.  We adjust the analyzer until the reading is what we know it ought to be.  This is called a “standardization.”

This procedure should be performed with each sensor connected to the analyzer to ensure accurate, repeatable readings.

New sensors must be standardized before use. Regular standardization is also necessary.

Analyzers with auto-recognition features enable the appropriate calibration screens to allow calibration for any single sensor configuration or dual sensor configuration of the analyzer. Remember, though: in many process conditions, auto-calibration may not work.

We manually standardize ORP analyzers, using a 1-point method. This means that the sensor will first be rinsed off, dried, placed in an mV solution, programmed, completing the standardization. The sensor is rinsed off and re-inserted into the process.

To calibrate the ORP loop with a connected ORP sensor, access the Calibration screen.

Choose an ORP buffer that is closest to the process you will be operating.  Once the sensor is placed in a buffer, allow time for the reading to stabilize. The temperature of the sensor is adjusting to the temperature of the buffer…

Most ORP analyzers follow the same methods for calibration. Choose Manual Calibrate or Select Manual Buffer entry, and follow the step-by-step procedures displayed on the analyzer screens…

Once the analyzer successfully completes the “calibration”, the values are reported at 25 °C for lab comparison purposes.