I. Determining the Intensity of On-Site Environmental Interference
Strong Interference Scenario (RC Filtering Must Be Enabled): The injection molding workshop has more than 3 frequency converters or servo motors; power lines and temperature sensing lines are laid on the same cable tray; there are strong electromagnetic radiation sources nearby, such as high-frequency welding equipment; the measured high-frequency spike pulse amplitude at the input end exceeds 50mV.
Weak Interference Scenario (RC Filtering Can Be Disabled): The workshop layout is neat; power lines and temperature sensing lines are laid separately and independently; there are no strong electromagnetic interference sources nearby; the measured high-frequency spike pulse amplitude at the input end is less than 10mV.
II. Determining the Temperature Sensing Signal Link Status
Temperature Sensing Line Length: If the temperature sensing line length exceeds 5 meters, interference is easily coupled during signal transmission, and RC filtering must be enabled; if the temperature sensing line length is less than 2 meters, the signal link is short, the probability of interference coupling is low, and RC filtering can be disabled.
Signal Anomaly Manifestation: When the temperature controller is unloaded, the temperature reading frequently fluctuates irregularly by more than ±3℃. Enabling RC filtering eliminates this fluctuation; filtering must be retained. If the temperature controller reading is stable without fluctuations, but enabling RC filtering results in a temperature sampling lag exceeding 2 seconds, filtering can be directly disabled.
III. System Hardware Performance Indicator Judgment
CMRR Measured Value: If the measured common-mode rejection ratio of the hot runner temperature control system is below 60dB, its common-mode interference immunity is insufficient; RC filtering must be enabled to supplement interference immunity. If the measured CMRR is above 80dB, the hardware itself has sufficient interference immunity; RC filtering can be disabled.
Ground Loop Status: If the system exhibits significant ground loop interference, with the ground potential difference between the two ends of the temperature sensing line exceeding 0.5V, enabling RC filtering can effectively suppress conducted interference; filtering must be retained. If the grounding performance is good, with the potential difference between the two ends below 0.1V, and there is no ground loop interference, RC filtering can be disabled.
IV. Reverse Judgment Based on Product Process Requirements
Ordinary Structural Component Molding: For components without extreme requirements for temperature response speed, enabling RC filtering can improve system stability; retaining it is recommended.
High-speed precision/optical grade transparent part molding: Temperature measurement response speed is required to be ≤2 seconds. The signal delay introduced by RC filtering will cause temperature overshoot and reduced temperature control accuracy. Therefore, RC filtering must be disabled.
