Research On The High Precision Digital Multimeter Based On DSP

In this paper, we study on the digital measurements of AC and DC electrical parameters of the high precision digital multimeter. We can measure the DC voltage, DC current, resistance, RMS (root-mean-square) of AC voltage and current.In this paper, the digital measurement theory of the AC and DC electrical parameters is introduced, and PWM-ADC (analog-digital conversion based on pulse width modulation technique) is used to DC electrical parameters measurement, indirect RMS/DC computation is used to RMS measure. We analyze the main reason of AC and DC error in measuring. According to the results of error analysis, selecting a suitable integral cycle and real-time self-calibration technique reduces the Power Line Interference, the gain and drift error. Frequency compensation algorithm is present in RMS measurement, it can reduces the measurement error, widens the measurement bandwidth and improve the response speed. After method study, We design the measurement system of the high precision digital multimeter based on the digital signal processor (TMS320VC5502) with low power consumption . The hardware of whole system is made of DSP module, ADC module, RMS measurement module composed of nine parts, etc. The software design include system initialization,A/D converter, data processing,keyboard and display. We carry out the experiment and the analyses of error. The methods and functions where we should improve are also discussed in the paper. The actual test results have verified the effectiveness and practicability of the algorithm and the developed system.High precision digital multimeter use digital measuring technology and digital signal processing technology. Software replaces much hardware, which is simple in configuration and simplify the peripheral circuit, portability and rich in function. The measurement system have high accuracy for AC and DC electrical signal with high practical value.