always adopts mechanical tinplate to measure。 There are some shortcomings that the measurement precision falls with machine abrasion， single time period setting and strong manpower ［2]。 In this paper， we propose a novel multi—rate three—phase watt—hour meter based on AT89LV52。 This multi-rate three—phase watt-hour meter adopts AD7752 for measurement. It has the characteristics which are time—sharing measurement， accurate measurement， LCD display， automatic meter reading， flexible time period setting, timely emendation， low cost and novel design。II。 STRUCTURE AND WORKING PRINCIPLEThe novel multi-rate three—phase watt-hour meter proposed in this paper is based upon AT89LV52 singlechip ［3]。 AT89LV52 has the flash memorizer with 8k bytes， cryptographical program memorizer with third class， RAM with 256 bytes, 32 programmable I/O lines， three time/ counter with 16 bits and a two class halt with six vectors。 The interface circuit adopts I2C bus unit which is a 8 bits singlechip with good performance and suitable price。 The system structure diagram is shown in figure 1。Figure 1。 System structure diagramThe principle of this multi—rate watt-hour meter is reading in themulti—rate time segments using RS485 bus and noting in X25045 then take over correctional clock with RS485 bus and write in clock CMOS chip S3530A. The three-phase AC voltage and electric current pass through potentiometer and mutual inductance instrument respectively so as to produce small signal which is sent to AD7752 to complete measurement. The clock CMOS chip S3530A gives clock information per second in the course of automatic move and analyze this clock belongs to which period of time according to advance periods of tim...
