Development Of The Temperature-Controlling Instrument Of VSM Based On MC9S12C32

The instrument has four main parts, one part is to collect temperature, one is to compute, one is to output and one is to display temperature. The main body of the instrument is connected with up-computer and the part that can control temperature.We use 16-bit chip MC9S12C32 made by Motorola in computing part. The actual temperature can be calculated by using the room temperature and the temperature which is collected by the temperature collecting part. Considering the time to measure the temperature and the precision of the data, we correct the error in computing process. Based on the measured temperature and the set temperature, we can get the output power by using the PID arithmetic. Then the signal of output power will be sent to the outputting part and the actual temperature will be sent to the face board to display.The temperature is collected by using the revised thermocouple. After the data of temperature has been changed by A/D board, it is sent to the chip for data processing.The displaying part will display the actual temperature in time using the LCD screen after it has received the data. This part is connected with the face-board of the instrument. We can set the parameter and temperature through the face-board.After the part for output makes the D/A change, the part that can control temperature will control the temperature finally. The calefaction resistance-thread is bind out of the cooling cavity. We can control the sample's temperature by adjusting the boiloff velocity of the liquid nitrogen by adjusting the power of the calefaction resistance-thread.In its working process, the instrument can connect its com-port with up-computer's com-port RS232 by the changing mains-level chip, then we can construct asynchronous serial interface. Based on the requisition for the temperature controlling, we can set the parameters in the computing part and the set temperature or the output part, process data collected by the hardware, can draw and save the picture of the data.This instrument has wider arrange of controllable temperature just using lower cost, has higher controllable precision, and can satisfy most VSM's request.The main body of the instrument has good electric characteristic by using reasonable layout, then decrease the effect on the other out instrument. So it can assure the veracity of the results when we do some experiment in low temperature using it. Because we use the blocking design, each part just sends the data to other part, and the data sent has unite format, we can satisfy lots of requests just through changing little instrument. That means we can get a serials of production.