PY909 absorbed the advantage of similar product aboard of the 90s,but it also has special characters, especially suitable for melt pressure measurement and control, and other grid fluctuation place, it has a beautiful exterior, compete function and excellent anti-jamming performance that makes system stable and reliable. It uses two rows of 4 bit digital tube to display actually pressure value and set value. Output windows single row barcode display power, top and low limit alarm can drive relays output voltage pulse, two-way SCR drives trigger permanent voltage(or current) output, auto panel debugging program, one button to calibration; the regulator chooses three immunity measures to make regulator stable working: first, adopting electric-light isolated circuit to separate input and micro processor, output separates with microprocessor, power source isolates with input, microprocessor, output; second, using immunity measure to make  sure software can work stably; third, using hardware to monitoring system to ensure system resume after interference. It is indicated that this design makes the system highly independent. Output power is synchronous PID, combined with fuzzy control, which makes manually control and auto control switch without interference. This series regulator is widely used in measuring and controlling the melt of pressure of petroleum, fiber, plastic and other industries.