In modern industrial automation and process control, sensors and transmitters are two indispensable components. They play a crucial role in monitoring and controlling various industrial parameters. Although they can be used interchangeably in some applications, they differ significantly in design, function, and application.
Transmitters and sensors play different roles in measurement and control systems, each with its own unique functions and applications. To understand these two types of devices, we can start by distinguishing them based on their definitions and functions.
As the name suggests, the core function of a sensor is sensing and transmission. It first senses the measured variable, such as temperature, pressure, liquid level, or flow rate, and then converts these sensed variables into non-standard electrical signals or other forms of output signals through a conversion element. Therefore, the key to a sensor's composition lies in the coordinated operation of its sensing and conversion elements.
Transmitters, on the other hand, focus more on signal transformation and transmission. Their working principle involves receiving non-standard electrical signals or other signals transmitted from sensors, processing them, and then outputting standard electrical signals, such as 4-20mA or 1-5V, for subsequent display, adjustment, and other operations.
From a functional perspective, sensors are crucial for acquiring information in both natural and industrial fields, playing an indispensable role in modern industrial production, especially in automated processes. Transmitters, on the other hand, are primarily responsible for detecting process parameters and transmitting these measurements as specific signals to support display, regulation, and other operations. In automatic detection and control systems, transmitters also transform various process parameters, such as temperature and pressure, into standardized signals before transmitting them to controllers and indicating recorders for processing.
1. Definition and Function
Sensor:
A sensor is a device that detects and responds to certain types of input from the external environment. These inputs can be in the form of light, heat, motion, humidity, pressure, etc. The main function of a sensor is to convert non-electrical signals (such as temperature, pressure, light intensity, etc.) into electrical signals so that subsequent electronic equipment can process these signals.
Transmitter:
A transmitter is a device that converts the output signal of a sensor into a standard signal (such as 4-20mA, 0-10V, etc.). A transmitter typically contains one or more sensors and has functions such as signal amplification, conversion, isolation, and linearization. The main purpose of a transmitter is to convert the sensor signal into a standardized signal suitable for long-distance transmission and control.
2. Signal Processing
sensor:
Sensors are typically only responsible for the initial detection and conversion of signals. They may not have sophisticated signal processing capabilities, and the output signal may require further amplification or conversion before it can be used for control or monitoring.
Transmitter:
Transmitters, on the other hand, include signal processing capabilities. They can amplify, linearize, and filter the sensor's output signal to ensure accuracy, stability, and suitability for use in industrial environments.
3. Output signal type
sensor:
Sensors can output various types of signals, including analog and digital signals, depending on the sensor's type and design. For example, a temperature sensor might output a voltage signal that is proportional to the temperature.
Transmitter:
The output signal of a transmitter is usually a standardized analog signal, such as 4-20mA or 0-10V. These signals are suitable for use in industrial automation systems because they have good anti-interference capabilities and long-distance transmission capabilities.
4. Installation and Use
sensor:
Sensors typically need to be installed directly near the physical quantity being monitored to ensure signal accuracy. Their installation location and method have a significant impact on the measurement results.
Transmitter:
Transmitters can be integrated with sensors or used as standalone devices. They are typically mounted in control cabinets or instrument panels for easy operation and maintenance.
5. Application Scenarios
sensor:
Sensors have a wide range of applications, from simple home automation to complex industrial process control. They can be used to monitor various physical quantities such as temperature, humidity, pressure, flow rate, and speed.
Transmitter:
Transmitters are primarily used in scenarios requiring the conversion of sensor signals into standardized signals, particularly in industrial automation and process control. They ensure signal consistency and reliability, facilitating system integration and remote monitoring.
6. Accuracy and stability
sensor:
The accuracy and stability of a sensor depend on its design and manufacturing quality. High-quality sensors can provide very accurate measurement results, but they may be sensitive to environmental conditions such as temperature and humidity.
Transmitter:
Transmitters improve signal accuracy and stability through built-in signal processing functions. They typically include features such as temperature compensation, linearization, and filtering to ensure the accuracy of the output signal.
7. Maintenance and Calibration
sensor:
Sensors may require regular maintenance and calibration to ensure the accuracy of their measurements. This may include cleaning, replacing parts, or recalibrating.
Transmitter:
Transmitters are typically designed to be easy to maintain and calibrate. They may include self-calibration capabilities or provide a simple calibration interface for users to perform regular calibrations.
8. Cost and Complexity
sensor:
The cost and complexity of sensors can range from very simple and inexpensive devices to highly complex and expensive systems. The choice of sensor should be based on application requirements and budget.
Transmitter:
Transmitters are typically more expensive and complex than standalone sensors because they incorporate additional signal processing and conversion capabilities. However, they offer higher signal quality and ease of system integration.
Transmitter
The name of the transmitter contains the words "transform" and "transmit." "Transform" refers to changing the signal, and "transmit" refers to transmitting it. In reality, transformation precedes transmission; therefore, transmission is the goal, and transformation is the foundation. The transformation section converts the non-standard electrical signals or other forms of signals transmitted from the sensor into standard electrical signals, such as 4-20mA or 1-5V, and then transmits the standard signals to the secondary instrument.
Distinguishing between sensors and transmitters based on their functions
Sensors are the main means and methods for acquiring information in the natural and production fields; sensor technology plays an important role in economic development and social progress; in modern industrial production, especially in automated production, various sensors are used to monitor and control various parameters in the production process, so that the equipment works in a normal or optimal state and the products achieve the best quality.
The function of a transmitter is to detect process parameters and transmit the measured values in a specific signal form for display and regulation. In automatic detection and control systems, its role is to transform various process parameters, such as temperature, pressure, flow rate, liquid level, and composition, into a unified standard signal, which is then transmitted to the controller and indicating recorder for adjustment, indication, and recording.
Distinguishing by the composition of sensors and transmitters
A sensor generally consists of four parts: a sensing element, a conversion element, a conversion circuit, and an auxiliary power supply. The sensing element directly senses the measured quantity and outputs a physical quantity signal that has a definite relationship with the measured quantity; the conversion element converts the physical quantity signal output by the sensing element into an electrical signal; the conversion circuit is responsible for amplifying and modulating the electrical signal output by the conversion element; the conversion element and the conversion circuit require an auxiliary power supply.
The transmitter mainly consists of a measuring section, an amplifier, and a feedback section. The measuring section detects the measured variable x and converts it into an input signal Zi that can be accepted by the amplifier. The feedback section converts the transmitter's output signal y into a feedback signal Zf, which is then sent back to the input. Zi is algebraically compared with the zero-adjustment signal Zo and the feedback signal Zf, and the difference ε is amplified by the amplifier and converted into a standard output signal y.
Distinguish by the signals acquired by sensors and transmitters
The sensor outputs a non-standard electrical signal or other forms of signal, which is a weak, non-standard signal.
The transmitter outputs a standard electrical signal, which is strong. For long distances, it transmits a standard current signal, while for short distances, it can transmit a standard voltage signal.
Distinguish by the output of the sensor and transmitter
The transmitter outputs standard electrical signals, such as 0-5V voltage and 4-20mA current.
The output of a sensor is not so standard; for example, it may be a very weak electrical signal. A transmitter necessarily contains a sensor, so it is essentially a sensor plus a power conversion device.
Distinguishing them by their wiring system and power supply.
Sensors come in two-wire, three-wire, and four-wire types; some require an external power supply, while others do not.
Transmitters are generally two-wire systems, with the power supply and signal connected to the same wire. Transmitters are used to convert the energy of a system into the same or different forms of energy; the key word is "conversion." The name "transmitter" includes the words "conversion" and "transmission." Conversion is the transformation, and transmission is the delivery. In reality, conversion comes first, followed by delivery; therefore, delivery is the goal, and conversion is the foundation. The conversion section transforms the non-standard electrical signals or other forms of signals transmitted from the sensor into standard electrical signals, such as 4-20mA or 1-5V, and then transmits the standard signal to the secondary instrument.
pressure transmitter
1. Wiring System and Power Supply: Sensors are available in two-wire, three-wire, and four-wire configurations. Some require an external power supply, while others do not. Transmitters are generally two-wire, with the power supply and signal wires sharing the same set of wires.
2. Signal: The sensor outputs a non-standard electrical signal or other forms of signal, which are weak non-standard signals. The transmitter outputs a standard electrical signal, which is strong. For long distances, a standard current signal is used for transmission, while for short distances, a standard voltage signal can be used.
3. Primary and Secondary Instruments: Transmitters and sensors are both primary instruments. Primary instruments are used for signal acquisition and conversion, while secondary instruments can receive signals acquired and converted by primary instruments and can be used for display, control, alarm, monitoring, and other applications.
The sensor and transmitter are integrated into one unit, which has the functions of both a primary instrument and a secondary instrument, and is called an intelligent transmitter.
Sensors convert physical quantities such as pressure and flow rate into electrical signals, while transmitters output these electrical signals as current or voltage signals that conform to certain standards, typically 4-20mA and 1-5V.
A sensor can convert signals into output signals according to a certain rule. When the sensor's output is a specified standard signal, it is called a transmitter. The following are the output signals of sensors and transmitters:
1. Current signal: 4-20mA 0-20mA
2. Voltage signals: 0-5V, 1-5V, etc., and also mV signals.
3. Resistance signal
4. Pulse signal
When the above signal output is changed to a standard 4-20mA signal, it is called a transmitter!
Concepts of transmitters and sensors
Transmitters and sensors are both important devices used in industrial automation. They are typically used to measure, acquire, and convert physical quantities such as temperature, pressure, and flow rate. A transmitter is a device that converts analog signals acquired by a sensor into a standard signal output, while a sensor is a device that converts physical quantities into electrical signals.
The difference between transmitters and sensors
1. Working principle:
A sensor converts a physical quantity into an electrical signal output, while a transmitter amplifies, filters, and linearizes the sensor's output signal before outputting a standardized electrical signal. Therefore, the two differ significantly in their working principles.
2. Function:
Sensors are typically used to monitor and measure physical quantities in real time, converting them into electrical signals. Transmitters, on the other hand, are used for the transmission, amplification, conversion, and isolation of electrical signals. They convert the sensor output signal into a standard format signal output to the control system, enabling the control system to monitor and control the measured physical quantity in real time, thus playing a crucial bridging role.
3. Application areas:
Sensors have a wide range of applications, including meteorology, environmental protection, biomedicine, and machining, while transmitters are mainly used in industrial automation. Transmitters can be widely used in petrochemical, power, metallurgy, machinery, aerospace, and computer industries. Their main function is to convert various physical quantities into standardized electrical signals, facilitating signal processing and control by the control system.
In summary, sensors and transmitters play distinct roles in measurement and control systems. Sensors are primarily responsible for sensing and transmitting the measured variable, while transmitters convert non-standard or other signals transmitted by sensors into standard electrical signals to support subsequent display, adjustment, and other operations. Furthermore, they differ significantly in their composition, output signals, wiring systems, and power supplies.
The transmitter's output signal is converted according to a specific standard.
Transmitters typically work in conjunction with sensors, which are responsible for integrating raw signals into a form that conforms to certain standards; this process is defined as transmission.
