ZPD-1000 series electric valve positioners produced by Changshu Changyi Instrument Co., Ltd. are the main supporting instruments of pneumatic actuators in industrial automation. They can be used to improve the linearity of valve position, overcome the friction of valve stem and eliminate the influence of unbalanced force of regulating valve. Therefore, the valve position is proportional to the current signal of 0-10mA(DC) or 4-20mA(DC) from the regulation instrument, which realizes the correct position. This series of products can be equipped with pneumatic diaphragm actuators, pneumatic piston actuators, direct acting regulators and angle regulators. In addition, this product has the dual functions of electric converter and pneumatic valve positioner. Therefore, it is widely used in petroleum, chemical, metallurgical, power, light textile, paper making and other industrial automation, and is an indispensable product in industrial automation instruments.