Emerson Rosemount 225, Reference Manual, Page: 21 / 32

Figure 3-3: Measuring standard temperature
Be sure air bubbles are not adhering to the sensor. An air bubble trapped in the
toroid opening has a particularly severe effect on the reading.
5. Turn off automatic temperature compensation in the transmitter.
This eliminates error in the cell constant.
6. Adjust the transmitter reading to match the conductivity of the standard.
3.3 Calibrating against a Referee - in-Process
Prerequisites
If possible, adjust the conductivity of the process liquid so that it is near the midpoint of
the operating range. If this is not possible, adjust the conductivity so that it is at least 5000
µS/cm.
Turn off automatic temperature compensation in the transmitter. This eliminates error in
the cell constant.
Procedure
1. Connect the process and referee sensors in a series.
Keep tubing runs between the sensors short and adjust the sample flow to as high a
rate as possible. Short tubing runs and high flow ensure that the temperature of the
liquid does not change as it flows from one sensor to another.
2. Allow the process liquid to flow through both sensors.
Orient the referee sensor so that the air bubbles always have an easy escape path
and cannot get trapped. Tap and hold the flow cell in different positions to allow
bubbles to escape.
Wait for readings to stabilize before starting the calibration.
3. Adjust the process sensor to match the conductivity measured by the referee
instrument.
Reference Manual Calibration
00809-0100-3225 August 2018
Rosemount 225 Sensors 21