Uncertainty in resistance measurements based on microcontrollers with embedded time counters

Author

Jordana, Josep ; Reverter, Ferran ; Pallas-Areny, R.

Author_Institution

Dept. of Electron. Eng., Tech. Univ. of Catalonia, Barcelona, Spain

Volume

2

fYear

2003

Firstpage

1078

Abstract

Microcontrollers with embedded time counters can measure resistance by determining the time needed to charge or discharge a given capacitor C. This paper analyzes the uncertainty and error in resistance measurements based on measuring the discharging interval depending on the value of C. Using the internal Timer1 of the PIC16F874, two calibration resistors, and averaging 1000 measurements, the relative error for resistors from 825 Ω to 1540 Ω and C = 220 nF, 1.5 μF, and 4.7 μF is below 0.2%, and the standard deviation for C = 1.5 μF, and 4.7 μF is below 0.3 Ω. Power supply noise greatly influences the uncertainty, which makes it essential to use power supply decoupling capacitors.

Keywords

counting circuits; electric resistance measurement; measurement errors; measurement uncertainty; microcontrollers; timing circuits; 1.5 muF; 220 nF; 4.7 muF to 6 F; 825 to 1540 ohms; embedded time counter; measurement error; microcontroller; power supply decoupling capacitor; power supply noise; resistance measurement uncertainty; Calibration; Capacitors; Charge measurement; Counting circuits; Current measurement; Electrical resistance measurement; Microcontrollers; Power supplies; Resistors; Time measurement;

fLanguage

English

Publisher

ieee

Conference_Titel

Instrumentation and Measurement Technology Conference, 2003. IMTC '03. Proceedings of the 20th IEEE

ISSN

1091-5281

Print_ISBN

0-7803-7705-2

Type

conf

DOI

10.1109/IMTC.2003.1207919

Filename

1207919