Four anti-interference technical measures for transducers(3)
4. Filtering technology
Filtering technology is to use a corresponding form of filter to filter out various interference signals, so that the interference signals during signal transmission will not enter the detection system. It is one of the most effective measures to suppress interference. Filtering technology is a widely adopted measure to suppress interference that is coupled to the circuit via wires. The filter of the corresponding frequency band is inserted into the signal transmission channel, and the interference signal is filtered out or attenuated as much as possible to achieve the purpose of improving the signal-to-noise ratio and suppressing interference.
Various filters are one of the effective measures to suppress differential mode interference. The filters commonly used in automatic detection systems are:
a. RC filter, when the signal source is a thermocouple, strain gauge and other sensors whose signal changes slowly, the use of a small, low-cost passive RC low-pass filter will have a better suppression effect on series mode interference.
b. AC power filter, the power network absorbs various high and low frequency noises, for which LC filters are commonly used to suppress the noise mixed into the power supply.
After inserting the AC power filter between the power supply and the load, the electromagnetic interference in the range of several thousand hertz to several tens of megahertz can be attenuated by more than several dozen times. The power supply of electrical equipment such as computers, sensors, and secondary instruments that work in an interference environment should preferably be connected in series with an AC power filter. The main considerations when selecting an AC power filter: First, the rated current of the filter must be greater than the working current of the electrical equipment; Second, within the foreseeable frequency range, the attenuation coefficient of interference must meet the requirements. When in use, you can choose a power filter that contains a first-level LC or two-level or even three-level LC according to your needs. It must be well grounded during use.
c. DC power supply filter, DC power supply is often shared by several circuits, in order to avoid mutual interference between several circuits through the internal resistance of the power supply, RC or LC decoupling filter should be added to the DC power supply of each circuit Device.
Corresponding measures can also be adopted for other disturbances such as thermal interference, temperature interference, light interference, etc., and thermal shielding can be used for thermal interference; temperature compensation can be used to compensate for temperature interference in order to adapt to temperature changes at the work site . In addition, in the design process, when selecting electrical components and sensors, devices with stable performance parameters, high reliability, and adaptability to specific work site conditions must be selected to ensure reliable and safe work after the system is composed.
In short, interference is a more complex technical problem. It should be fully considered in the design process for different technical requirements, different working environments, types of interference sources, interference channels, and other specific situations. Anti-interference measures make the system work reliably and normally. (Copyright switch fuse group copyright) For example, shielding technology is used in the actual design of truck scales and railroad scales. Multi-core cable with shielding layer is used for signal transmission; shielding technology is used in the system zero adjustment device. Through the use of corresponding measures, the system operates reliably and weighs accurately. Anti-interference measures such as shielding technology and grounding technology are also used in the automatic batching system using belt weighing in the cement production process to ensure the system's batching is accurate. In the heat treatment process control, thermocouple sensors or thermal radiation temperature sensors are used as measuring elements. In order to ensure the normal operation of the system, considering the influence of high temperature working environment, heat shielding technology, temperature compensation technology, Photoelectric coupling technology, etc., makes the temperature control more accurate, and the heat treatment process of the parts also meets the technical requirements.
