In the previous article, we introduced the noise phenomenon of pressure transmitters and how to reduce the noise of the main pressure noise. Many customers have reported whether other types of transmitters also have noise phenomena. Today, we will comprehensively and in detail explain the noises that transmitters may encounter. Only by finding the source of transmitter noise can we find a better noise reduction method to improve the performance and service life of the transmitter. In general, there are mainly the following types of transmitter noise The first type: low-frequency noise Low-frequency noise is mainly caused by the discontinuity of the internal conductive particles. In particular, carbon film resistors have many tiny particles inside their carbonaceous materials, and the particles are discontinuous. When current flows through, the conductivity of the resistor will change, causing the current to change, and produce a flash arc similar to poor contact. In addition, transistors may also produce similar burst noise and flicker noise. The generation mechanism is similar to the discontinuity of the particles in the resistor and is also related to the doping degree of the transistor. The second type: shot noise generated by semiconductor devices Due to the change in the voltage of the barrier region at both ends of the semiconductor PN junction, the amount of charge accumulated in this area changes, thus showing a capacitive effect. When the current passes through, it causes tiny fluctuations, thus generating current noise. The size of the noise generated is proportional to the temperature and the bandwidth △f. The third type: high-frequency thermal noise High-frequency thermal noise is generated by the irregular movement of electrons inside the conductor. The higher the temperature, the more intense the electron movement. The irregular movement of electrons inside the conductor will form many tiny current fluctuations inside it. Because it is disordered movement, its average total current is zero, but when it is connected to the amplifier circuit as a component (or as part of the circuit), the current inside it will be amplified and become a noise source, especially for the circuit working in the high-frequency band. The fourth type: interference of electromagnetic components on circuit boards Many circuit boards have electromagnetic components such as relays and coils. When current passes through, the inductance of the coil and the distributed capacitance of the shell radiate energy to the surroundings, and the energy will interfere with the surrounding circuits. Components such as relays work repeatedly, and when the power is turned on and off, a momentary reverse high voltage will be generated, forming a momentary surge current. This momentary high voltage will have a great impact on the circuit, thereby seriously interfering with the normal operation of the circuit. Fifth: Transistor noise Transistor noise mainly includes thermal noise, shot noise, and flicker noise. Thermal noise is caused by the irregular thermal motion of carriers passing through the body resistance of the three regions in the BJT and the corresponding lead resistance. The emitter current or collector current has irregular fluctuations, which will produce shot noise. The noise caused by the poor surface cleaning of the transistor due to the semiconductor material and manufacturing process level is flicker noise. Sixth: Resistor noise The interference of resistors comes from the inductance and capacitance effects in the resistors and the thermal noise of the resistors themselves. Seventh: Integrated circuit noise There are generally two types of noise interference in integrated circuits: one is radiation and the other is conduction. These noise spikes will have a greater impact on other electronic devices connected to the same AC power grid. For any questions about product consultation, product customization, agency, technical inquiry, quotation, etc., please contact Xingyi: 400-600-4496!