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High voltage transients, such as lightning and electrostatic discharge, can be interpreted as false open sensor conditions, resulting in open sensor alarms that can disrupt process control. Referencing the Operator Trend Views above, the transmitter interprets the lightning strike as a short series of open senor events and, as shown in the view on the left, goes into an alarm state.
The Rosemount 3144P features Open Sensor Holdoff, which gives the 3144P time to determine if an Open Sensor event has actually occurred, or if there has been a false Open Sensor condition due to a high voltage transient. During this time, it reports a good sensor reading, as shown in the right graph in the image above.
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A temperature sensor subjected to a high vibration or noisy environment can report these influences as false temperature spikes, as shown in the Operator Trend View on the left in the image above.
The Rosemount 3144P features the capability Intermittent Sensor Detection, which recognizes these intermittent temperature readings as incorrect and rejects them from the measurement. Instead, the 3144P reports the last known temperature, as shown in the Operator Trend View on the right side of the image above. By filtering out these incorrect temperature spikes, Intermittent Sensor Detection helps avoid disruptions in process control.
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Because of the low amplitude of their signal, temperature sensors can easily pick up noise from a 50 or 60Hz AC voltage source (e.g. a pump, a variable frequency drive, or power lines).
AC voltage interferences are interpreted in the transmitter as a part of the temperature measurement, causing an incorrect reported temperature.
The Line Voltage Filter can be customized at 50 or 60 Hz, depending on the frequency of the supply voltage, allowing the transmitter to recognize the influence of an AC voltage interference and filter out this noise– resulting in a more accurate reading.
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On temperature installations utilizing an RTD sensor type, corroding terminations or damaged sensor wiring can create small voltages called “thermal EMFs.” These small voltages are transmitted down the sensor wiring and can cause a shift in the temperature readings reported by the RTD.
The Rosemount 3144P features Emerson's patent-protected EMF Compensation. EMF Compensation monitors RTD sensor loops and filters out small voltages, allowing the transmitter to provide sensor measurements that are unaffected by thermal EMFs, resulting in a more reliable temperature measurement.
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A quality calibration holds the key to an accurate interpretation of measurement values. If an unwanted trim is performed (for example, if an as-found as-left evaluation request was misinterpreted), an incorrect calibration will affect the reliability of the measurement. The Rosemount 3144P is designed with a Recall Factory Trim feature, which is able to revert the transmitter calibration back to the sensor information originally stored in the device.
Recall Factory Trim prevents the transmitter from losing all calibration information, enabling the ultimate "undo" of any accidental calibration and protecting transmitter integrity.
