May 20, 2013
To get the highest accuracy with a pressure transducer you need an output signal which has a high resolution and can not be easily corrupted. Unlike analogue output signals, digital signals do not suffer from interference or signal loss. With digital output signals either the complete signal gets through as originally transmitted or nothing gets through at all.
To get a high resolution output signal a powerful analogue to digital converter is needed. The converter needs to have at least a 16bit resolution to give precision levels better than 0.01% full scale. There is no need to convert a digital signal to analogue between the pressure transmitter and logging instrumentation. This is because it can be easily interfaced using a digital connection to either a data acquisition card or computer.
One more benefit for using digital output signals is that the microprocessor located inside the pressure transducer can be used to digitally characterise the pressure transmitter across lots of temperature and pressure points. This helps to eliminate nearly all linearity errors.
The accuracy of a digital pressure transducer will always be limited to the repeatability and hysteresis of the sensor technology being used. Repeatability and hysteresis factors are unpredictable and are very difficult to characterise. Digital outputs have the potential to give the most accurate signal but it must be used along with stable sensing technology. This technology needs to have naturally low hysteresis and repeatability to be truly accurate over its entire operational life.
The most common interface for general applications is RS485. Manufacturers often supply desktop software for communicating with the pressure transmitter via a specific converter box.
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