Development of a current to pressure (I/P) converter. System analysis of a current to pressure (I/P) converter through physical modelling and experimental investigation, leading to a design for improved linearity and temperature independence.

Abstract

Current-to-pressure (I/P) converters are pneumatic devices which provide precise control of pressure in various industries – for example these devices are often used in valve positioner systems (typically found in the oil and gas industry) and tensioning systems (typically used in the packaging industry). With an increasing demand for such devices to operate in harsh environments all by delivering acceptable performance means that Current-to-pressure converters need to be carefully designed such that environmental factors have no or minimal effects on its performance. This work presents an investigation of the principles of operation of an existing I/P converter through mathematical modelling. A simulation model has been created and which allows prediction of performance of the I/P converter. This tool has been used to identify areas of poor performances through theoretical analysis and consequently led to optimisation of certain areas of the I/P converter through a design change to deliver improved performances, for instance the average percentage shift in gain at 1mA input signal (over the temperature range of -40°C to 85°C) on the new I/P converter is 2.13% compared to the average gain of 4.24% on the existing I/P converter, which represents an improvement of almost two fold. Experimental tests on prototypes have been carried out and tests results showed that improved linearity and temperature sensitivity can be expected from the new design.