TRANSMITTER WITH AN IMPROVED SPAN ADJUSTMENT.

摘要

A TRANSMITTER (200) SENSES A PROCESS VARIABLE AND PROVIDES A TWO-WIRE OUTPUT ADJUSTED BY A SPAN ADJUSTMENT. A SPAN-CONTROLLING CIRCUIT IS COUPLED BETWEEN THE SENSOR AND THE OUTPUT CIRCUIT AND RECEIVES A SPAN ADJUSTMENT. THE SPAN-CONTROLLING CIRCUIT INCLUDES AN AMPLIFIER COUPLED TO A POTENTIOMETER. THE WIPER OF THE POTENTIOMETER IS CONNECTED TO THE AMPLIFIER OUTPUT (228) SO THAT ONE PORTION OF THE POTENTIOMETER RESISTANCE PROVIDES FEEDBACK FROM THE AMPLIFIER OUTPUT (228) TO THE AMPLIFIER INPUT(222). A SECOND PORTION OF THE POTENTIOMETER RESISTANCE IS COUPLED BETWEEN THE AMPLIFIER OUTPUT (228) AND THE OUTPUT CIRCUIT.(FIG. 4)