MVME5500-0161 The design scheme of anti-interference in the interface circuit of pressure sensor is made
Every pressure sensor interface circuit has a small signal processing problem, because the output of the sensor is generally a small signal, the maximum amplification to the required signal (such as 0 ~ 5V), and can achieve the required technical indicators, you must pay attention to some problems not expressed on the circuit diagram, that is, anti-interference problems. A discussion is necessary before further discussion of the selection of circuit elements, circuits and system applications.
Interference can be roughly divided into three aspects:
1, local generation (that is, unwanted thermocouples).
2, the coupling inside the subsystem (that is, the path problem of the ground wire).
3, MVME5500-0161 external generation (that is, power frequency interference).
In low-level measurements, strict attention must be paid to the materials used in the signal path. Solder, wires, and terminals encountered in simple circuits can generate actual thermoelectric potential. Since they often appear in pairs, it is a very effective measure to keep these pairs of thermocouples at the same temperature as far as possible, for this purpose, heat shielding, heat sink, arrangement along the isotherm or separation of high-power circuits and low-power circuits is generally used, and the purpose is to reduce the thermal gradient to the smallest. The contact of two different manufacturers of standard wires may produce a temperature drift of 0.2/1V / ° C, MVME5500-0161 which is equivalent to the temperature drift of a high-precision low-drift pipe, and twice the temperature drift of a chopping amplifier. Elimination of external and local interference AC signals can be coupled to low electronic analog circuits by distributed capacitors and inductors, and DC high voltage through leakage conductance can be coupled to high impedance inputs, which can introduce interference that can be eliminated by proper layout of components, shielding and protection.
The proper layout of components involves maintaining the greatest possible distance between high and low energy and between digital and analog circuits, while the wiring between ground lines requires the shortest possible distance.
MVME5500-0161 The shielding includes electrostatic and electromagnetic shielding. The interference field generated by the power transformer is well-known, and it is not easy to explain the source of interference, you can use a shielded transformer or put the power supply away from the highly sensitive circuit. However, the same circuit needs to be tapped close to the center of the transformer to achieve high quality grounding, but also may be subject to strong magnetic field interference, if necessary, to determine the reasonable layout by testing methods.
The electrostatic and electromagnetic interference of 50HZ power supply can be controlled by minimizing the loop area, or using twisted pair and limiting the frequency band in the low frequency circuit.
In short, MVME5500-0161 the anti-interference problem of the interface circuit is one of the important measures to get a high-quality signal, the lower the output signal of the sensor, the selection of the amplifier components of the interface circuit, and the more stringent the anti-interference measures are required, but the larger the signal of the sensor will affect the nonlinear characteristics of the sensor output, which is contradictory. In practical application, it should be considered that under the condition of linearity, the output sensitivity of the sensor should be improved as much as possible, including improving the bridge pressure and other measures, under normal circumstances, the output sensitivity of the sensor can reach 1 ~ 3mV/V, and it is not hoped to reduce the sensitivity of the sensor in exchange for the improvement of other technical indicators of the interface.