Thermal resistance temperature acquisition based on USB data acquisition card (DAQ) and IO module "suggestions collection"

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Simakehua's scheme for temperature acquisition of thermal resistance temperature sensor

Introduction to thermal resistance

Here we mainly introduce platinum thermistor ,Pt100 Platinum thermistor , Its resistance is proportional to the change of temperature .PT100 The relationship between resistance and temperature change is ： When PT100 The temperature is 0℃ Its resistance value is 100 ohm , stay 100℃ Its resistance is about 138.5 ohm . Its industrial principle ： When PT100 stay 0 At centigrade , Its resistance is 100 ohm , Its resistance will increase at a constant rate as the temperature rises . There are three main wiring modes of national standard thermistor ： Two line system ： The method of connecting a wire at both ends of the thermal resistance to lead out the resistance signal is called two-wire system ： This lead method is very simple , But because the connecting wire must have lead resistance R, resistance R The size of the wire is related to the material and length of the wire , Therefore, this lead method is only suitable for occasions with low measurement accuracy . Three wire system ： Connect a lead at one end of the root of the thermal resistance , The method of connecting two leads at the other end is called three wire system , This method is usually used together with the bridge , It can better eliminate the influence of lead resistance , Three wire system is the most commonly used lead resistance in industrial process control . Four wire system ： The method of connecting two wires at both ends of the thermal resistance root is called four wire system , Two of the leads provide constant current for the thermal resistor I, hold R Convert into voltage signal U, Then through the other two leads U Lead to secondary instrument . It can be seen that this lead way can completely eliminate the resistance influence of the lead , It is mainly used for high-precision temperature detection .

Temperature transmitter

When using thermal resistance for temperature acquisition , What Sima Kehua company provides here is USB-3000 Series of data The acquisition card collects the temperature （ The most common signal received by data acquisition card is voltage signal ）. Thermal resistance PT100 The sensor output type is resistive , With the increase of temperature, the resistance value increases , Therefore, the temperature transmitter is needed to convert the resistance change of thermal resistance into a standard signal that can be recognized by the acquisition card , It is usually converted into voltage and current signals , The temperature transmitter selected here converts the resistance change into voltage signal . Pictured 1.1 Temperature transmitter .

                                         chart 1.1 Temperature transmitter 

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Connection between data acquisition card and temperature transmitter

This mainly explains the connection between the temperature transmitter that can output standard voltage and the data acquisition card . The temperature transmitters used here are 6 Terminals , Respectively, the power supply for the temperature transmitter is , Power supply negative （ Power ground ）,A terminal , Two B terminal , There are also output terminals （ Interface of standard voltage output ）. You need to choose a suitable power supply for the temperature sensor （ The specific power size needs to be selected according to the manual of the temperature transmitter ）, The three wire connection mode is adopted here , Refer to the introduction of thermal resistance for specific wiring mode . Then according to the picture 1.2 Interconnection . The following figure uses the wiring diagram given by the output voltage form of the temperature transmitter , It can be adapted to general data acquisition card . If the temperature transmitter used is output 4—20ma electric current , For wiring, you need to refer to the topic of collecting current data with the acquisition card in the knowledge base of the official website of Sima Kehua . link ：http://www.smacq.cn/knowledge/typical/current.html.

                                         chart 1.2 Connect the data acquisition card with the temperature transmitter 

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Here are the following instructions for the connection between the data acquisition card and the temperature transmitter , Usually power the temperature transmitter , It will be ignored whether the power supply of the temperature transmitter is grounded with the data acquisition card . If you don't share , Then the temperature transmitter is the floating source relative to the acquisition card , So we need to follow the figure 1.2 To connect , take AI Sense And AGND Make a short circuit . If it can be determined that the acquisition card is grounded with the temperature transmitter , You don't have to be right AI Sense And AGND Make a short circuit , The negative power supply can be directly connected with AI Sense Just connect . The specific wiring method of floating source and grounding source needs reference USB-3000 A series of manuals . Data acquisition card software operation First, before using the temperature transmitter , You need to know some important parameters of the used temperature transmitter , Know whether the selected temperature transmitter conforms to the model of thermal resistance , Power supply voltage of temperature transmitter , Temperature range , What is the output voltage . ad locum , When Sima Kehua actually did the test , The selected power supply voltage is 24V, The temperature range is -50℃—400℃, Output voltage 0V—10V Temperature transmitter . Next, I will enter Sima Kehua Smacq DAQ Software Set the interface , Set the single ended mode adopted by the software , Selection is AI 0 Channel for data collection . The range is ±10.24V, The sampling rate is 10Sa/s/ch（ In the actual acquisition, it can be set according to the actual situation and the existing sampling rate of the acquisition card ）, Then you need to set the range and output voltage of the temperature transmitter , Pictured 1.3 Temperature transmitter parameters .

                                       chart 1.3 Temperature transmitter parameters 

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If it is necessary to convert the voltage signal collected by the acquisition card into temperature , Here you can check unit transformation . Pictured 1.4 Voltage curve collected by acquisition card , Pictured 1.5 The temperature curve collected by the acquisition card through unit transformation .

                                        chart 1.4  Voltage curve 

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                                         chart 1.5  Temperature curve 

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In this way, the voltage curve and temperature curve collected by the acquisition card can be obtained , Then you can also export the collected data by using the software function provided by Sima Kehua , Get the voltage and temperature generated by the collection Excel Data in tabular form . For the software operation of data acquisition card, please refer to 《Smacq DAQ Software Quick use guide 》.

long-range IO The module collects data of thermal resistance

The above scheme is for data acquisition card USB-3000 Series of thermal resistance temperature acquisition , Of course, there is another scheme of using thermal resistance to collect temperature data , It is launched by Sima Kehua company M2100 Series of M2111 long-range IO modular ,M2100 Series temperature acquisition remote IO Module is based on Modbus RTU Computer interface module of standard protocol . Two types of thermal resistors can be supported, namely PT.CU, The data interface is RS-485(2 Line ), For specific information, please refer to the product manual on the official website of Sima Kehua . Because of the present PC There are few machines 485 Interface , Sima Kehua company provides SDS1000 Serial converter , It USES USB Standard agreement , Can support RS-232 and RS-485 Transformation .

long-range IO modular M2111 And thermal resistance PT100 Wiring diagram for

The first thing to use is SDS1000 Serial converter and M2111 long-range IO modular , There is also a power supply equipment ,M2111 The supply voltage is 9V—30V. Pictured 1.6IO Schematic diagram of connection between module and thermal resistor .

                                      chart 1.6 IO Schematic diagram of connection between module and thermal resistor 

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The above connection is the thermal resistance temperature collection of Sima Kehua company , Given remote IO Wiring diagram of the temperature acquisition system built by the module .（ It should be noted that do not connect 485 The interface line is connected reversely , And pay attention to the wiring mode of thermal resistance , The three wire connection mode is adopted here ） After the wiring is correct , You can operate the software provided by Sima Kehua company to collect temperature .

long-range IO modular M2111 Software operation

First, according to the remote IO For the model of the module, please refer to the product manual to download the remote IO Software corresponding to the module M Console, On the basis of identifying serial port and communication , To set up with remote IO Parameters related to module product model , For specific settings, please refer to IO Product manual of the module . The following schematic diagram shows the software settings and thermal resistance of Sima Kehua company when testing products PT100 Examples of temperature acquisition .

                                       chart 1.7 Basic parameter settings 

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                                      chart 1.8  Temperature acquisition interface 

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You can also click the data record table on the main page Data logger, Select the channel to record the temperature for data acquisition , Then set the address of file generation , The collected temperature data can be displayed in real time , And the collected temperature data can be generated .CSV A table of formats , It is convenient for users to analyze data . Pictured 2.0 Data waveform .

                                       chart  2.0 Data waveform 

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The above are the two schemes for temperature acquisition of thermal resistance temperature sensor given by Sima Kehua company , Customers can choose their own data acquisition card or... According to their actual situation and required functions M2111 long-range IO modular .

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