Emerson Exchange 365

Temperature sensors, such as thermocouples and RTDs (resistance-temperature detector), can degrade over time due to harsh process conditions, vibration, and other factors.

• On-scale Errors- when the output of a transmitter is within process alarm limits yet does not accurately indicate actual process information
• Invalid measurement readings that lay outside of alarm limits when actual process variable is within acceptable range
• Abnormally fast process rates of change

These issues are often due to failing sensors (most common), electronic interference, corroded termination points, loose electrical connections, high vibration and runaway reactions. These conditions can lead to unnecessary shutdowns, inefficient energy usage, off-spec product, lower yields and unsafe process conditions. The measurement validation diagnostic can detect these measurement abnormalities and help plant staff take preventive action before they become a major issue, saving time and money associated with process shutdowns and helping processes run more efficiently.

As a temperature sensor starts to degrade, its signal noise will increase resulting in unreliable readings. Measurement Validation works by monitoring the signal noise and using it to calculate a deviation value indicating the magnitude of this noise. This calculated deviation value is then compared to a user selectable limit, which, if exceeded, can alert plant staff of an unreliable measurement point and possible sensor degradation.