Card-mounted vortex flowmeter parameters
The vortex flowmeter is based on the Karman vortex principle to measure the volume flow of gas, steam or liquid, the volume flow or mass flow of standard conditions.
View MoreIn industrial automation control systems, temperature measurement is a crucial link.
Transmitter and temperature sensor wiring diagram
In industrial automation control systems, temperature measurement is a crucial link. The temperature sensor is used to sense temperature changes and convert them into electrical signals, while the transmitter converts the weak signal output by the sensor into a standard signal for subsequent instrument display, control and recording. This article will introduce in detail the wiring method of the transmitter and temperature sensor, and provide common wiring diagrams to help you quickly master the relevant knowledge.
1. Temperature sensor types and output signals
There are many types of temperature sensors, the common ones include thermocouples, thermal resistors, etc. Different types of sensors have different output signals, so special attention needs to be paid when selecting the transmitter and wiring.
1. Thermocouple
A thermocouple is a loop composed of two different metal materials. It uses the Seebeck effect to convert the temperature difference into an electric potential difference. Common thermocouple types include K-type, J-type, T-type, etc. The corresponding temperature range and sensitivity of each type are different. The thermocouple output signal is a millivolt voltage signal, and its positive and negative values are related to the measured temperature and cold junction temperature.
2. Thermal resistor
Thermal resistor is a sensor that uses the resistance value of a metal conductor to change with temperature to measure temperature. Common types of thermal resistors include Pt100, Pt1000, etc. The output signal is the resistance value, usually between a few ohms and several hundred ohms. Thermal resistance requires a bridge circuit or constant current source circuit for measurement.
2. Transmitter type and function
Transmitters can be divided into thermocouple transmitters, thermal resistance transmitters, and millivolt/current transmitters according to the input signal type. Devices etc. Its main function is to convert the weak signal output by the sensor into a standard current signal (4-20mA) or voltage signal (0-5V, 0-10V), and perform signal amplification, isolation, linearization and other processing to improve signal transmission. distance and anti-interference ability.
1. Thermocouple transmitter
The thermocouple transmitter is specially designed for thermocouple signals. It integrates a cold-end compensation circuit and can automatically eliminate the influence of the cold-end temperature on the measurement results. influence. Users need to select the appropriate transmitter based on the type of thermocouple used.
2. Thermal resistance transmitter
Thermal resistance transmitter is specially designed for thermal resistance signals. It usually uses a three-wire or four-wire connection method internally to reduce the wire resistance. influence on measurement results.
3. Millivolt/current transmitter
The millivolt/current transmitter can receive millivolt-level voltage signals or current signals and convert them into standard 4- 20mA current signal or 0-5V, 0-10V voltage signal. This type of transmitter can be used to convert and amplify various sensor signals.
3. Transmitter and temperature sensor wiring diagram
The following are several common transmitter and temperature sensor wiring diagrams:
1. Two-wire system Thermocouple transmitter wiring diagram
Instructions:
+: Positive pole of power supply, usually 24VDC. -: Negative pole of power supply. T+: positive terminal of thermocouple. T-: negative terminal of thermocouple. I+: Current output positive pole, connected to PLC or other control system. I-: Current output negative pole. 2. Three-wire thermal resistance transmitter wiring diagram
Instructions:
+: Positive pole of power supply, usually 24VDC. -: Negative pole of power supply. A: One pin connection end of the thermal resistor. B: The other pin connection end of the thermal resistor. C: The third pin connection end of the thermal resistor is used to compensate for the wire resistance. I+: Current output positive pole, connected to PLC or other control system. I-: Current output negative pole. 3. Four-wire heating resistance transmitter wiring diagram
Instructions:
+: Positive pole of power supply, usually 24VDC. -: Negative pole of power supply. A: One pin connection end of the thermal resistor is used to measure current. B: The other pin connection end of the thermal resistor is used to measure voltage. C: The third pin connection end of the thermal resistor is used to compensate for the wire resistance. D: The fourth pin connection end of the thermal resistor is used to compensate for the wire resistance. I+: Current output positive pole, connected to PLC or other control system. I-: Current output negative pole. 4. Precautions
When wiring the transmitter and temperature sensor, you need to pay attention to the following matters:
Select the appropriate transmitter and sensor type to ensure its measurement range and accuracy. Meet the requirements. Correctly connect the positive and negative poles of the sensor and transmitter to avoid reverse connection and burning the equipment. Use shielded cables for signal transmission and do grounding to reduce interference. Set the correct parameters according to the transmitter manual, such as range, zero point, output mode, etc. Before powering on, carefully check whether the wiring is correct, and then power on and debug after confirming it is correct. In short, the correct connection of the transmitter and temperature sensor is the key to ensuring the normal operation of the temperature measurement system. We hope that the wiring methods and precautions introduced in this article can help you better perform related work and ensure that your automation control system operates stably and reliably.
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