The newest application of isolation amplifier: field analog signal bandwidth and isolation transmitter frequency response matching technology
Post date:2018-09-13 16:49:13    View: times    
In the case of slowly changing frequency (< 50Hz) (measuring temperature / displacement / flow, etc.), low frequency response isolation amplifier with small bandwidth can be selected: ISO EM U-P-O-M (M for low frequency response) series products. In the case of high frequency variation (> 2KHz), high and low frequency response isolation amplifier can be selected: ISO EM U-P-O-H (H meter). In addition to high frequency response and low frequency response environment, most industrial sites choose conventional frequency response products: ISO EM A-P-O. Optoelectronic isolation amplifier: ISO U(A)-P-O series should be selected when there is space interference (high frequency/high voltage and high current load) in the field environment.
Summary: The analog signal isolation amplifier (also called analog isolation transmitter) between industrial field sensors and PLC / FCS / DCS, instruments and meters belongs to the category of analog signal conditioning. Analog signal isolation amplifier can effectively protect all levels of control circuit, eliminate or weaken the impact of environmental noise on the test circuit, restrain the interference of common ground, inverter, solenoid valve and surge pulse to the equipment, at the same time, it has the function of signal voltage limiting and choking to the subordinate equipment. It is a reliable protective device for transmitter, instrument, frequency converter, solenoid valve, PLC / DCS input and output and its communication interface. For some industrial sites with harsh environment, the control system is intricate, high temperature, vibration, humidity and interference signals coexist, so amplifying, transforming, remote transmitting the input and output analog signals by isolation amplifier and completely isolating the system circuits are indeed effective measures for anti-interference in today's automatic control system. One of.
Bandwidth, also known as band width, refers to the amount of data that can be transmitted at a fixed time, that is, the ability to transmit data in a transmission pipeline. In digital devices, bandwidth is usually expressed in BPs, that is, the number of bits per second. In analog devices, the bandwidth is usually expressed in the transmission cycle per second or Hertz (Hz). The bandwidth of a signal refers to the frequency range occupied by various frequency components contained in the signal.
Frequency response, referred to as frequency response, is used electronically to describe the difference in the processing ability of an instrument, PLC and other equipment for different frequency signals. Like distortion, this is also a very important parameter index.
The test method of bandwidth index is as follows. A sine wave analog signal with adjustable frequency is added to the input, and the maximum frequency range in which the output can stably follow the input signal is bandwidth. What is the engineering significance of the bandwidth index of the industrial signal isolation amplifier? How do we understand "bandwidth" in applications? The bandwidth index reflects the response speed of the isolation amplifier to changes in the input signal. The larger the bandwidth, the faster the isolation amplifier responds to the change of the signal; the smaller the bandwidth, indicating that the isolation amplifier is insensitive to the instantaneous change of the input signal, which in some cases means that the isolation amplifier has stronger anti-dry ability.
The working principle of isolation amplifier and isolation transmitter is firstly to modulate the standard signal or special signal such as temperature, displacement, frequency, rotational speed transmitted and received by sensors, instruments and PLC through semiconductor devices, and then to isolate and convert the signal into precision by optical or magnetic sensors. The original signal with the same linearity can be transformed into other signals, and the working power supply of the signal before and after the isolation can be isolated to ensure the signal input, the signal output and the auxiliary power supply, that is, the signal before and after the transformation, the power supply and the ground are separated. Analog signal isolation amplifier and isolation transmitter belong to one of the devices in the classification of industrial instruments and sensors. Their main functions are isolation, amplification, conversion and transmission of analog signals. Therefore, there must be a basic technical index of signal bandwidth and frequency response.
Industrial site signal transmission interference processing reference scheme (frequency converter anti EMC interference isolation amplifier):
There are many EMC interference sources in industrial field, such as frequency conversion control equipment, high-power electromagnetic starting equipment, GPS high-frequency signal wireless transceiver and so on.
1. Interference from analog output of sensor output.
Adding ISO series analog signal isolation amplifier to the output of the sensor can effectively solve the attenuation and EMC interference in the process of analog signal transmission, and enhance the stability and reliability of the display control system. Analog signal isolation amplifier for frequency converter anti-EMC interference: ISO EM U-P-O-M series, is to install input signal interference suppression filter circuit and output interference harmonic absorption circuit in IC to enhance anti-EMC electromagnetic interference and high-frequency signal spatial interference function. It is especially suitable for the occasions where there are frequency conversion control equipment, high-power electromagnetic starting, GPS high-frequency signal wireless transceiver.
2. The spatial interference of high frequency signal radiation.
The control systems and equipments are equipped with metal shielding boxes (the metal components used in different frequency bands are different) and the enclosures are grounded reliably. Twisted pair shielding cables are used for signal transmission lines.
3, RS232/RS485's remote communication line interference.
A DC-DC isolation module power supply is installed on the RS232/RS485 communication interface to isolate the communication power supply directly from other power supply. The transmission line of signal communication also adopts double shielded cable (shielding grounding).
4. Interference in the power supply circuit of the system
Large current thyristor, frequency conversion control equipment and high power electromagnetic starting device will have distortion effect on power supply parameters of power system. through
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