Field Matching Techniques for Instrumentation and Sensor Signal Bandwidth and Frequency Response

发布时间:2021-10-09 08:47:27  Number of views:1094order

Overview: The analog signal isolation amplifier (also known as analog isolation transmitter) belongs to the category of analog signal conditioning for the input and output between industrial field sensors and PLC/FCS/DCS, instruments and meters. Analog signal isolation amplifier can effectively protect all levels of control circuits, eliminate or attenuate the impact of environmental noise on the test circuit, inhibit the public ground, frequency converters, solenoid valves and surge pulses on the interference of the equipment, and at the same time on the lower level of the device has a signal voltage limiting, choking function. It is a reliable protection device for transmitters, instruments, frequency converters, solenoid valves, PLC/DCS input/output and their communication interfaces. For some of the harsh environment of the industrial site, the control system is complex, high temperature, vibration, humidity and interference signals coexist, so through the isolation amplifier will be the input and output analog signals for amplification, conversion, telecommunication and complete isolation of the various system circuits is indeed one of today's automation control systems in the anti-jamming of effective measures.

         Band width, also known as bandwidth, refers to the amount of data that can be transmitted at a fixed time, i.e., the ability to pass data through a transmission pipeline. In digital equipment, bandwidth is usually expressed in bps, i.e., the number of bits that can be transmitted per second. In analog equipment, bandwidth is usually expressed in cycles per second or hertz (Hz). The bandwidth of a signal is the range of frequencies occupied by the different frequency components of the signal.

        Frequency response, or frequency response for short, is used in electronics to describe the difference in the ability of an instrument, PLC, etc. to handle signals of different frequencies. Like distortion, it is also a very important parameter.

        The test method of bandwidth index is as follows, a frequency adjustable sine wave analog signal is added to the input, and the maximum frequency range in which the output can stably follow the signal at the input is the bandwidth. Industrial signal isolation amplifier bandwidth indicators of engineering significance? In the application of how we understand & ldquo; bandwidth & rdquo; it? Bandwidth indicators reflect the response speed of the isolation amplifier to changes in the input signal. The larger the bandwidth, the faster the response of the isolation amplifier to signal changes; the smaller the bandwidth, indicating that the isolation amplifier is insensitive to instantaneous changes in the response to the input signal, in some occasions also means that the dry resistance is stronger.

         The working principle of isolation amplifier and isolation transmitter is that the standard signals sent and received by sensors, instruments, PLCs, etc. or special signals such as temperature, displacement, frequency, rotational speed, etc. are modulated by semiconductor devices, and then converted and transmitted through isolation by optical or magnetic sensing devices, and then demodulated and restored to the original signals of the same precision and linearity, or transformed into other signals, and the working power supply is isolated to ensure that the signal input and signal output and auxiliary power supply, i.e. the signals before and after transformation, the power supply and the ground are triple isolated. At the same time, the signal before and after the isolation of the working power supply isolation process to ensure that the signal input, signal output and auxiliary power supply, that is, before and after the transformation of the signal, power supply, ground between the three isolation. Analog signal isolation amplifier and isolation transmitter belongs to the classification of industrial instrumentation and sensors in a device, its main function is the isolation of analog, amplification, conversion and transmission, and therefore there must be a signal bandwidth and frequency response of this basic technical indicators.


 Industrial field signal transmission interference processing reference program (frequency converter anti-EMC interference special isolation amplifier)

Industrial sites have frequency control equipment, high-power electromagnetic starting equipment, GPS high-frequency signal wireless transceivers and other EMC interference sources of the system, the need for different sources of interference and the characteristics of the system control signal to analyze and determine the interference signal processing solutions. 

1, the sensor output analog signal interference

   Adding ISO series analog signal isolation amplifier at the output of the sensor can effectively solve the attenuation and EMC interference during analog signal transmission, and enhance the stability and reliability of the display control system. Analog signal isolation amplifier for inverter anti-EMC interference: ISO EM U-P-O-M series, is installed inside the IC input signal interference suppression filtering circuit and output interference harmonic absorption circuit, to enhance the 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 starter, GPS high-frequency signal wireless transceiver device on site.

2, high-frequency signal radiation space interference

  The control system, equipment were installed metal shielding box (different frequency bands use different metal components) and the shell is reliably grounded, signal communication transmission lines using twisted shielded cable.

3, RS232 / RS485 remote communication line interference

  In the RS232/RS485 communication interface on the installation of DC-DC isolation module power supply, the communication power supply and other power supplies directly isolated from each other. Signal communication transmission lines should also use twisted shielded cable (shielding layer grounded).

4, the system power supply circuit interference

  The site has a high-current thyristor, frequency control equipment, high-power electromagnetic starting device, the power supply system will have an aberrant effect on the power supply parameters. Through the power supply circuit, the interference signal will enter the site of the various control devices. Therefore, the first thing to make sure that the site of each device is well grounded, the power supply of each device should be installed with its matching power filter (low-pass EMI filter or suppressor reactor).


Analog signal isolation amplifier isolation transmitter bandwidth and frequency response industrial field technical indicators selection and application reference:

1, analog signals in the slow frequency of change (<50Hz) occasions (such as measurement of temperature, pressure, displacement, flow, etc.), you can choose a smaller bandwidth, low-frequency ringing isolation amplifiers: ISO EM U (A)-P-O-M series of products (M: indicates a low-frequency ringing). So in the inverter control system, in order to inhibit and isolate EMC interference, often choose: ISO EM U-P-O-M series of isolation amplifier.

2, analog signals in the change of high frequency (> 2KHz) occasions (such as measuring speed, adjusting high-speed electronic switches, switching power supply PWM control, etc.), in order to protect the integrity and reliability of the collected data, is often used to select the high bandwidth, high and low-frequency response isolation amplifiers: ISO EM U (A) - P - O - H series of products (H: that is, the high-frequency response).

3、Most systems outside the high-frequency and low-frequency response environment choose conventional frequency response (2K) products: ISO EM A-P-O or ISO EM U-P-O series.

4, on-site environment with strong magnetic space interference (high-frequency electromagnetic high-current load) occasions can choose optoelectronic isolation amplifier: ISO U (A)-P-O-M series.

Signal Isolator/Isolation Amplifier/Isolation Transmitter IC size and PCB size reference (SIP12 Pin)



Isolation Amplifier Isolation Transmitter IC, Typical Application Wiring Diagram for ISO EM Series (ISO EM A-P-O / ISO EM U-P-O)


Zero, Gain Adjustable Isolation Amplifier IC, Typical Application Wiring Diagram for ISO EM-T Series (ISO EM A-P-O-T / ISO EM U-P-O-T)


Input Isolated Distribution Isolated Transmitter IC: Typical Application Wiring Diagram for ISO EM-S Series (ISO EM A-P-O-S / ISO EM U-P-O-S)


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