A voltage transmitter typically consists of the following components:
1. Sensor: Used to sense and measure monitored physical quantities, such as temperature, pressure, and liquid level. Sensors convert these physical quantities into electrical signals for output.
2. Signal conditioning circuit: Receives the electrical signal generated by the sensor and processes it by amplification, filtering, linearization, etc., to ensure that the output electrical signal is accurate, stable, and meets specific standards and requirements.
3. Output circuit: Converts the processed electrical signal into a standard voltage output, typically a 4-20mA current output, but other types of voltage output are also possible.
4. Power supply: Used to provide the power required for the voltage transmitter, usually using DC or AC power.
When selecting a voltage transmitter, the following key factors need to be considered:
5. The physical quantity to be measured: Determine the physical quantity to be measured, such as temperature, pressure, flow rate, etc.
6. Measurement range: Determine the required measurement range, including minimum and maximum measurement values, to ensure that the selected voltage transmitter can meet the required measurement range.
7. Environmental conditions: Consider factors such as temperature, humidity, and vibration of the working environment to select a voltage transmitter that can adapt to these conditions.
8. Output type: Determine the required output type. Usually, voltage output and current output are available. Select the appropriate output type according to the system requirements.
9. Accuracy and stability: The accuracy and stability requirements of the voltage transmitter are considered to ensure the accuracy and reliability of the measurement results.
10. Power Supply: Determine the applicable power supply type and voltage range to ensure that the selected voltage transmitter can function properly.
11. Installation and wiring method: Select a voltage transmitter that meets the specific installation requirements and wiring method.
Taking all the above factors into consideration, a suitable voltage transmitter can be selected to meet specific measurement and control needs. During the selection process, it is advisable to consult the manufacturer or professional technicians to ensure that the most suitable voltage transmitter is chosen.
Part 1: Working Principle of Voltage Transmitters
A voltage transmitter is a device that converts a measured physical quantity into a voltage signal output. Its working principle is based on a combination of a resistor bridge circuit and an amplifier circuit.
1. Resistor bridge circuit
A common resistor bridge circuit used in voltage transmitters consists of four resistors. Three of these resistors are known resistors, called reference resistors, and the fourth resistor is the resistor to be measured. By applying an input voltage to the bridge and applying the bridge balance condition, the value of the resistor to be measured can be calculated.
2. Amplifier circuit
A voltage transmitter amplifies the minute voltage signal calculated by a resistor bridge circuit to improve the signal's sensitivity and stability. The amplification circuit typically includes differential amplifiers, filters, and linear amplifiers.
3. Output voltage signal
The amplified voltage signal will be used as an output signal and sent to the control system or recording equipment. Common output signal types are 0-10V or 4-20mA.
Part Two: Selection Methods for Voltage Transmitters
Choosing the right voltage transmitter is crucial for ensuring measurement accuracy and system reliability. Here are some selection guidelines:
4. Measurement range and accuracy:
Determine the required measurement range based on actual needs, and ensure that the voltage transmitter's measurement range covers this range. At the same time, pay attention to the accuracy of the voltage transmitter and select an accuracy class that meets the requirements.
5. Physical properties:
Consider the characteristics of the physical quantity being measured, such as temperature, pressure, and flow rate. When selecting a voltage transmitter, ensure that it is suitable for the operating conditions of the physical quantity being measured.
6. Output signal type:
Determine the required output signal type; common types are 0-10V or 4-20mA signals. Select the appropriate output signal type based on the requirements of the control system.
7. Environmental factors:
Consider the environmental factors in which the voltage transmitter operates, such as temperature, humidity, and vibration. Ensure that the selected voltage transmitter has the ability to adapt to these environmental requirements.
8. Installation and connection methods:
Select the appropriate voltage transmitter mounting method based on the actual installation conditions, such as flange mounting, DIN rail mounting, or plate mounting. At the same time, ensure that the connection method is compatible with the control system.
9. Reliability and quality assurance:
Choose a voltage transmitter brand with reliability and good quality assurance, and obtain product manuals and technical support in a timely manner to ensure convenient subsequent maintenance and troubleshooting.
10. Cost-effectiveness:
Taking into account factors such as price, performance, and reliability of voltage transmitters, select products with higher cost-effectiveness.
Part Three: Application Examples of Voltage Transmitters
Voltage transmitters are widely used in various industrial fields. Here are some application examples:
11. Pressure Measurement
Voltage transmitters are used to measure pressure in pipes, containers, or equipment. The voltage signal, after appropriate amplification and processing, can be used in control systems to monitor and control pressure.
12. Temperature Measurement
By connecting a temperature sensor, a voltage transmitter can measure and control temperature. For example, during heat treatment, a voltage transmitter can transmit temperature signals to a control system, enabling precise temperature control.
13. Flow measurement
By combining a differential pressure sensor and a voltage transmitter, the flow rate of liquids or gases can be measured. Accurate flow rate values can be obtained by analyzing the output signal of the voltage transmitter.
14. Liquid Level Measurement
Voltage transmitters can be used in level sensors to measure the level of liquids or solids. By transmitting the voltage signal to the control system, the level can be monitored and controlled.
A voltage transmitter is an important industrial measuring instrument. Its working principle is based on a combination of a resistance bridge circuit and an amplifier circuit. By converting the measured physical quantity into a voltage signal output, it enables the measurement and control of various physical quantities. When selecting a voltage transmitter, factors such as measurement range, accuracy, physical characteristics, environmental factors, output signal type, installation method, quality assurance, and cost-effectiveness need to be considered. Correct selection and application of voltage transmitters can improve system reliability and measurement accuracy, thereby meeting the needs of industrial automatic control systems.
