| Temperature transducers such as thermocouples and platinum resistances play very important roles in industry scene and process control. Many connection ways of transducers are lineate, and this is not very convenient. So we develop the high precise digital temperature with wireless communication, temperature signal processor and MCU. The system adopts wireless receive and dispatcher single chip nRF401 whose transmitting power is 10dBm and transmission distance is 20m indoors or 100m outdoors. The system is made up of three parts by functions. The first part is composed of platinum resistance temperature transducer, temperature signal adjustment circuit and central controlling unit. The second part is the wireless transmitting part that is composed of wireless receiving and transmitting single chip and central controlling unit. The wireless receiving and transmitting unit is nRF401 that is produced by Nordic corp. from north Europe. The third part is the long-distance controlling unit. This function can be chosen. The controlling unit transmits data and controlling order through RS-232. The circuit adopts CS5532 chip that adjusts the electronic bridge out signal and realizes the A/D transmission in 24 bits. CS5532 adopts super sampling technology and has high transmitting digits (24bits) and supports SPI interface protocol and is easy to connect MCS51 MCU. The 1 pin and 2 pin are simulation temperature input pins. PT100 receives the temperature change and then the output voltage of electronic bridge changes. The voltage connects the 1 pin and 2 pin. The MCU calculates the temperature by the input voltage. A 22 nF capacitance is between the 3 pin and the 4 pin. The 5 pin connects the positive pole (+2.5V) of simulation power supply and the 6 pin connects the negative pole (-2.5V) of simulation power supply. AD7660 transmits +5v voltage to –5v voltage and provides ADC with negative benchmark power supple. The crystal 4.9152MHz is between the 9 pin and the 10 pin. The 11 pin, the 12 pin and the 13 pin are SPL (serial protocol interface) that is the simplest serial communication protocol. The 11 pin connects the 21 pin of MCU by isolation part and its function is the clock of serial communication. The 12 pin connects the 23 pin of MCU by isolation part and its function is the data output pin of serial communication. The 13 pin connects the 22 pin of MCU by isolation part and its function is the data input pin of serial communication. The function of the isolation part is reducing disturbance and making the communication more stabile and improving the communication efficiency. The 14 pin connects the grounding. The 15 pin connects +5v power supple. The 16,17,19,20 pin connect the grounding. The 18 pin connects 2.5v benchmark voltage. The circuit adopts the wireless receiving or transmitting single chip nRF401 whose function is transmitting temperature data and measuring command wirelessly. It adopts FSK modulation/demodulation technology and has low error coding and is easy to connect PC. The highest transmitting velocity is 20kHz. If we want to achieve the wireless receiving or transmitting of temperature data we can use the I/O port of MCU set up and control the receiving/transmitting module of nRF401 and gate choice module.The third part is long-distance controlling part programmed by visual programming TESTPOINT. The Program can measure, save and print the temperature parameter and demand history register. TESTPOINT is a visual programming soft on GUI (graphic user interface) by America Capital Equipment Corporation. TESTPOINT is easy to implement various communications and its math calculation capacity is very good. The visual long-distance controlling programming system has several functions: (1)long-distance measuring; (2)data display; (3)data recording; (4)data saving; (5)data printing; (6)inquiring history recording.It is convenient for data to connect external programming interface by CODE widget. Using long-distance controlling programming can make measuring very eas...
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