A 6(1/2) Digit Low Cost High Precision Dmm Desing/Study

Digital multi meter,it is a test measurement instrument which can transfer natural analog signal to discrete digital signal,and quantized to data.A multi-ramp ADC based DMM can reach very high resolution and numbers of data and test speed.Current,it universal used on high precision DMM,Picoammeter,Nanovoltmeter,Sourcemeter and others high end test and measurement instrument.In this thesis,we studied a Multi-ramp ADC based DMM design which can completed resistor,AC/DC voltage and AC/DC current test function.And this thesis mainly discussed the model of the 5 test functions,floating power supply and Multi-ramp ADC,and explained how to achieve high resolution and how to reduce cost.Multi-ramp ADC added reference voltage verification during integral process that reduced a lot dynamic range and improved resolution and test speed,and minimized the bypass circuit impacting,and the number of times of switch circuit has no impact to single.It used on many commercial instrument because it's low cost.