Integrated RK803 sensor for transmitting vibration signals of rolling bearings

transmitterconcept

atindustryIn process control, the measurement transmission unit, actuator, and regulator make up the entire systemcontrol systemThe three major components. The measurement and transmission unit is the transmitter, sometimes the transmitter is actually equivalent tosensorAnd actuators are like valves, regulators arecontrollerIt is the brain of the entire control system.

Sensors and transmitters together constitute automatic control monitoringsignalSource. A transmitter is a device that converts the output signal of a sensor into a signal that can be recognized by a controller, or converts the non electric input of the sensor into an electrical signal and amplifies it simultaneously, converting it into a standard signal source (such as 4-20mA DC)power supply）Can be used for remote measurement and control. Therefore, the transmitter is not only a conversion medium, but also a medium.

The process in automatic control is: signal source -->sensor -->transmitter -->arithmetic controller -->actuator -->control output.

In industrial sites, sometimes transmitters and sensors are interchangeable because the output signals of most modern sensors are already signals that can be received by a universal controller, and this signal can be directly recognized by the controller without being converted by the transmitter. Similar to sensors, transmitters are generally divided into temperature/humidity transmitters, pressure transmitters, differential pressure transmitters, and liquid level transmitters,currentTransmitter, power transmitter, flow transmitter, weight transmitter, etc.

Principle of transmitter

'Change'——Transformation refers to the process of converting various physical quantities from sensors into electrical signals. For example, using thermocouples to convert temperature into electrical potential; Using a current transformer to convert high current into low current. for another examplehumidity sensorisChange according to changes in humiditycapacitorofcapacitanceMeasure the quantity to calculate the relative humidity in the air.Due to the ease of processing electrical signals, modern transmitters convert various physical signals into electrical signals.

'Sending' - refers to the process of transmitting various electrical signals that have already been transformed, in order to facilitate the reception and transmission of other instruments or control devices, and then passing them through againelectronic circuitUnify the electrical signals from the sensors (e.g. 4-20mA, 0-5V). The method is through multiple meansoperational amplifierTo achieve. For example, the GS512 ducted temperature and humidity transmitter from Haigu can convert and transmit standard 4-20mA signals from the temperature and humidity module.

Signal transmission andpower supplyClassification of wire systems

Second line system:In the heatresistanceThe method of connecting a wire to each end of the wire to extract a resistance signal is called two-wire system: this wiring method is simple, but due to the inevitable existence of wire resistance r when connecting wires, the size of r is related to the material and length of the wire, so this wiring method is only suitable for situations with low measurement accuracy;

three-wire system：The method of connecting a lead at one end of the root of a thermal resistor and two leads at the other end is called the three wire system. This method is usually used in conjunction with an electric bridge to effectively eliminate the influence of lead resistance and is commonly used in industrial process control.The thermal resistor adopts a three wire connection method. The use of a three wire system is to eliminate measurement errors caused by the resistance of connecting wires. This is because the circuit for measuring thermal resistance is usually an unbalanced bridge. As a bridge arm resistor of the electric bridge, the thermal resistor's connecting wire (from the thermal resistor to the central control room) also becomes a part of the bridge arm resistor. This part of the resistor is unknown and varies with the ambient temperature, causing measurement errors. Adopting a three wire system, one wire is connected to the power terminal of the bridge, and the other two wires are respectively connected to the bridge arm where the thermal resistance is located and the adjacent bridge arm, thus eliminating measurement errors caused by the resistance of the wire line；

Four wire system: The method of connecting two wires at each end of the root of a thermistor is called a four wire system, in which two leads provide a constant current I to the thermistor, convert R into a voltage signal U, and then lead U to the secondary instrument through the other two leads. It can be seen that this lead method can eliminate the influence of lead resistance and is mainly used forhigh precisionthe temperaturedetection.

Primary and secondary instruments

The explanation of secondary instruments is to accept the use of transmitterstransformerThe electrical or gas signals sent by sensors (including thermocouples, thermistors) indicate the process technology being detectedparameterInstruments for measuring values. Taking physical objects as examples, such as digital displays, temperature controllers, etc. A primary meter belongs to signal acquisition and conversion (various transmitters, temperature components, signal acquisition devices), and a secondary meter is used for display alarm adjustment (panel mounted display alarm instruments, input of distributed control systems, input of distributed control systems).

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