For example, HART protocol-based multivariable mass flow transmitters sense three process variables (pressure, temperature, and differential pressure). Using these variables, they perform an internal calculation to derive mass flow. The mass flow information is transmitted as a standard 4…20 mA signal to the control system. Unfortunately, unless you have a HART-based control system, there is no way to continuously monitor the additional non-primary variables that are used to make the calculation.
Still, monitoring these variables may be desirable if one or more of the variables is especially important to the quality or safety of the process. In such a scenario, the HART Loop Converter extracts useful information from the multivariable transmitters that was previously not available.