Design Of A Handheld LCR Meter Based On MSP430

This paper designs a new type of handheld LCR meter for electronic measurements. This meter can measure resistance R, capacitance C, inductance L and other related arguments.This meter is composed of signal generate circuit, half-bridge measurement circuit, phase-sensitive detector circuit, A/D converter, microprocessor, keyboard array, LCD and so on. In the design of standard signal generator circuit, a FPGA (Field Programmable Gate Array) chip and filter circuit are used to get precise frequencies for measurements and for the clock of A/D converter. The half-bridge circuit has four standard resistances and several high precision operational amplifiers. It can choose appropriate standard resistances for different measurements for auto range setup. This system also has the function of amplifying the weak signal to get the precise sample data. The phase-sensitive detecting circuit, high precise dual slop A/D converter and free coordinate axis theory make the system have higher precision. The microprocessor in this system is MSP430F449 of MSP430 series produced by Texas Instruments Incorporated. The functions of system are controlled by a keyboard array, and the array is composed of 9 keys based on the interrupt technology of MSP430F449. Two methods of keys control are used. The data of measurement are displayed on LCD, and the main display has 5 digits, the vice display has 4 digits.This system has many functions, which are L/C/R choose, measurement frequencies choose, industry frequency interference choose, data hold, flash data access, voltage test, beep and so on.The hardware design and software arithmetic implementation are also described in this paper. Error analysis is done based on large amount of test data. This meter has higher precision, lower consumption and smaller size. The basic precision is about 0.5%. The limit setup ranges are that R: 1Ω～10MΩ; L: 10uH～100mH; C: 100pF～10uF, the basic accuracy of the meter is 0.5%, the power supply is 9V and the current consumption is 50mA～60mA. 29 figures, 14 tables, 28 reference literatures are included in this paper.