In order to reduce installation and operational costs, process plants have ofter used RTDs or thermocouples without a transmitter for temperature measurement. This is especially true for high density temperature measurements like distillation columns, reactors and bearings on rotating equipment. However, there are a number of disadvantages to this strategy and high density temperature transmitters offer an economical solution.
The biggest downfall of a direct RTD temperature measurement is you do not have any insight into the quality of the measurement. If an RTD is no longer working or the sensor has drifted, you will not be aware of it. The more critical the process temperature, the greater the impact this will have on your process reliability. Transmitters take the RTD signal and convert it to an analog output and most have HART capabilities. This allows for alerts and calibration of temperature measurement.
However, if there are a number of temperature measurements to be made, like in a distillation column, reactor or rotating equipment, having a temperature instrument for every point can be cost prohibitive. High density temperature transmitters are now commonly used for these applications. They can accept up to four (4) RTD input and then transmit them via the HART values (PV, SV, TV, QV). Many will also accept other types of inputs, so any device with a resistance or millivolt output can be used.
Similar to a standard temperature transmitter a high density temperature transmitter will allow for alerts and calibration. This will allow you to maintain your process temperature, produce product more efficiently and provide greater reliability. High density temperature transmitters are also available with a WirelessHART output making the measurement even most cost affordable. Not a bad idea!
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