Positioner

Abstract

The present invention provides a voltage inputting-type positioner of an inexpensive structure wherein, through a simple change relative to the common electric current inputting-type positioner, there will be no excessively large electric current even if connected to the voltage supply side without connecting a load resistance, so that communication will also be possible without impediment. A voltage / current converting circuit (1-5) is provided in a stage prior to a communication circuit (1-2). An over-current preventing circuit (CB) is incorporated into the voltage / current converting circuit (1-5). The voltage / current converting circuit (1-5) converts a DC voltage signal (V) into a DC electric current signal (V), and converts an AC voltage signal (Vf) into an AC electric current signal. Moreover, the voltage / current converting circuit (1-5) keeps the excessively large electric current that would flow into the internal circuitry thereof to no more than a predetermined electric current value (for example, no more than 30 mA) when the positioner (1C) is connected in error to the voltage source side without a load resistance (6) connected.

Description

technical field [0001] The invention relates to a positioner. The positioner receives a DC signal from an upper side system through a pair of wires. On the one hand, it generates its own working power from the DC signal; on the other hand, it controls the opening of the regulating valve according to the value of the DC signal. . Background technique [0002] Conventionally, this type of positioner is designed to operate by a 4 to 20 mA current (direct current signal) sent from the host system via a pair of wires. For example, if the control valve is a proportional valve, the opening of the proportional valve is 0% when a current of 4mA is supplied from the upper system, and the opening of the proportional valve is 100% when a current of 20mA is supplied. [0003] In this case, since the supply current from the host system varies within the range of 4mA (lower limit current value) to 20mA (upper limit current value), the internal circuit of the positioner is And can always ...

AI Technical Summary

Problems solved by technology

[0012] In this case, the manufacturer of the supply positioner must prepare a current input type positioner and a voltage input type positioner in order to ensure the communication function with the upper side system, and to support the on / off valve, or to support the field bus method. Two types of positioners, thus creating a burden on manufacturing

In addition, since it is necessary to prepare a voltage input type positioner which is different from a general current input type positioner, it causes a high price.

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