【正文】 es the efficiency of the multipoint temperature test system seriously. In this paper, DS18B20 are hung on some I/O buses by grouping DS18B20 evenly, and the conversion temperature data is obtained by reading the state of DS18B20, then the system loss decreases and the alternate test speed increases obviously, which won’t influence the precision and the reliability of the conversion. A set of multipoint temperature test of artificial environment laboratory is achieved in this paper, which increases the test efficiency of the former system. 2. CHARACTERISTICS OF DS18B20 DS18B20 is the single bus digital temperature sensor from American Dallas Company. DS18B20 is consisted of the 64 figures ROM engraved by laser, the temperature sensitivity ponent, nonvolatile temperature alarms trigger (Device TH and TL).DS18B20 municates with the microprocessor by the single bus port and the test range of DS18B20 is from 55 centigrade to +125 centigrade, and the incremental value is centigrade. The temperature can be changed into figures within 720ms and each DS18B20 has the sole 64 figures serial number. Fig 1 DS18B20 64bit ROM The specific content is revealed as Fig 1: There are two 8 figures storages ( and ) for storing temperature value in DS18B20. storage stores plement of the temperature value, and stores symbols of the temperature value. The user can define nonvolatile temperature alarms sets and distinguish the alarms search order and seek the ponent temperature alarms state outside the scheduled limit. There are two alternative ways of power supply: Signal bus highlevel borrow power is adopted, or the +5v power supply externally is adopted directly. 3. APPLICATION THE GROUPING TEST METHOD This paper illustrates the grouping method with the interface of DS18B20 and 89C52. Assuming the amount of the buses on P1 port is 4 and the temperature test system needs 100 DS18B20 sensors, which can be distributed equally to the 4 I/O lines. If the number of sensors cannot be divided by the number of buses even, the number disparity of sensors on buses is no more than one, which can be handled while reading numbers. The power is supplied externally. Owning to the synchronistic conversion in each DS18B20, the intense current is needed, and the signal bus cannot be used for the power supply, otherwise the system cannot work in order. The schematic circuit is shown as Fig 2 (the DS18B20 signal buses of the same group are hung on some buses of P1 port). When read and write the DS18B20, the strict schedule must be kept. First a reversion pulse is sent to all DS18B20. After the reversion, Skip ROM order is sent to each circuit simultaneously from the I/O port, and the conversion order is sent, then all sensors begin transform. After the conversion, Match Rom order is sent to each circuit simultaneously, and 64 bits serial number is sent. DS18B20 is selected for each group, and Scratch Pad data is read. Finally the data is transformed. The data of serialread is transformed into the actual temperature value. One alternate test is finished after the DS18B20 temperature data is read pletely by the cyclical reading for 25 times. Fig 2 DS18B20 grouping sketch map Now the timeconsuming in the test system of the single bus and the grouping analyses method is illustrated respectively. The reversion time sequence and the time sequence of writing and reading one bit for the microprocessor are revealed in figures 46. The figure show: The reversion period of DS18B20 is 495us1020us。 the reading period of one bit is above 60us。 the specific measures must be taken according to the heat release of the shell. This paper designed a set of wireless temperature using DS18B20 grouping mode test system for testing the temperature of the asphalt transportation vehicle shell, and the total points is 120. Temperature test system software adopts the modular design. The hypogenous machine collects data, stores data, sets up DS18B20, and sends the wireless module and so on. The epigenous machine adopts PC machines, mainly receives the temperature data from the hypogenous machine. The epigenous machine displays, stores and manages data. The simple munication between people and machines is performed by the epigenous machine. This paper will not illustrate the simple procedure of the epigenous machine in detail. The following is the illustration of parts of hypogenous machine. hardware Considering the multipoint temperature number of the temporary storage and the considerable internal RAM during the value conversion, the chief controlling chip adopts ATMEL 89C52 SingleChip Microputer with 256 bytes RAM and 8KB E2PROM procedure storage. As the distinguishable code of DS18S20 is read and numbered, the liquid crystal module (Ao Kela Chinese integrated module of OCMJ Jin Peng Company) and the keyboard module are added. The wireless digital transmission adopts the wireless module 375 in the whole receptionsending form, which may has two amateur bands to choose and the regulative Baud Rate ( the max is 20Kbit/s), and the SingleChip Microputer serial port data can be received directly. DS18B20, with the power supply, divided into 8 groups hung on P1 port (). The wireless module is hung on serial port directly and the hardware watchdog adopts the MAX813 chip. When the power is added to the system, the reversion signal is transmitted from the MAX813 reversion pin, and the value of the reversion pulse is 200ms. When the procedure is in order, a pulse signal must be sent to MAX813 WDI pin in no more than the interval of to clear away the watchdog timer. If the interval is more than , the pin does not receive the pulse signal, and then the 89C52 must be reversed. As 120 DS18B20 serial numbers must be stored in the system, the data storage DS1225 (8K) against the power failure i