A traditional analog transmitter is fairly simple and straightforward. Typically, there are two types of possible adjustments: zero and span. Configuring, testing and calibration are all accomplished by changing these two adjustments to set the correct relationship between the input pressure and the 4-20 mA output.
HART transmitters are considerably more complex. Like the older analog transmitters, HART transmitters have the same pressure input and 4-20 mA output, but in addition to the analog current loop output, there are a number of digital variables and settings contained in the device. Accessing these digital parameters requires the use of a HART configurator or communicator, and is critical to maintaining these devices. In fact, with many HART devices there is no way to maintain them without being able to gain access to the digital parameters.
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