I. Core Functions
Suppressing High-Frequency Interference: Filters out high-frequency electromagnetic pulses and spike noise coupled to the input, preventing abnormal temperature reading fluctuations and false heating triggering.
Smoothing Signal Waveforms: Filters and shapes the weak temperature measurement signal transmitted by thermocouples, reducing signal ripple and improving temperature sampling accuracy.
Protecting the Input Port: Absorbs instantaneous overvoltage at the input, preventing high-voltage spikes from impacting the internal sampling circuit of the thermostat and extending hardware lifespan.
II. Selection Criteria
Conditions for Retaining RC Filtering: The presence of strong electromagnetic interference sources such as frequency converters and servo motors in the field; temperature sensing cable length exceeding 5 meters; frequent temperature controller reading fluctuations exceeding ±3℃; and a measured system CMRR (Common Mode Rejection Ratio) below 60dB.
Criteria for canceling RC filtering: The temperature sensing cable is less than 2 meters long, there is no significant electromagnetic interference on site, and the temperature signal response lag exceeds 2 seconds, leading to severe temperature sampling lag and overshoot during the heating process.
III. Advantages and Disadvantages
Advantages: Extremely low hardware implementation cost, no need to modify software logic, can directly filter out more than 90% of high-frequency conducted interference, significantly reducing signal link noise levels.
Disadvantages: Introduces signal transmission delay, reduces temperature measurement response speed, and improper filter parameter settings can lead to temperature sampling lag, causing overshoot and decreased temperature control accuracy.
IV. Typical Application Scenarios
Required Scenarios: Cluster layout of multiple large injection molding machines in injection molding workshops, power lines and temperature sensing cables laid on the same cable tray, and severe grounding loop interference in the hot runner system.
Recommended Scenarios for Disabling: High-speed precision injection molding, optical-grade transparent part molding, and high-precision temperature control scenarios requiring a temperature measurement response speed of ≤2 seconds.
Flexible scenario adjustment: In ordinary small and medium-sized injection molding workshops, the balance between anti-interference capability and temperature measurement response speed can be found by adjusting the RC time constant, so as to take into account both stability and control accuracy.
