A digital signal-processing instrument for impedance measurement (original) (raw)
Related papers
DSPIC-Based Impedance Measuring Instrument
Metrology and Measurement Systems, 2011
An implemented impedance measuring instrument is described in this paper. The device uses a dsPIC (Digital Signal Peripheral Interface Controller) as a processing unit, and a DDS (Direct Digital Synthesizer) to stimulate the measurement circuit composed by the reference impedance and the unknown impedance. The voltages across the impedances are amplified by programmable gain instrumentation amplifiers and then digitized by analog to digital converters. The impedance is measured by applying a seven-parameter sine-fitting algorithm to estimate the sine signal parameters. The dsPIC communicates through RS-232 or USB with a computer, where the measurement results can be analyzed. The device also has an LCD to display the measurement results.
Implementation of DSP based algorithms for impedance measurements
ICSPC 2007 Proceedings - 2007 IEEE International Conference on Signal Processing and Communications, 2007
In this paper, two DSP based algorithms are implemented for impedance measurements. The algorithms (the sevenparameter sine-fitting algorithm and the ellipse fitting algorithm) are implemented and tested in a commercial DSP kit. The complete system is used to compare the algorithms by measuring 105 different impedances, using the four-wire impedance measurement method. The strategic selection of appropriate reference impedances, intrinsic to the impedance measurement method, is also described. The results of each algorithm are compared in terms of speed and accuracy. This is the ground work for a portable DSP based impedance measurement device to be implemented in specifically designed hardware.
Impedance measuring system based on a dsPIC
2010
This paper describes a device based on a dsPIC (Digital Signal Peripheral Interface Controller) as a processing unit, capable of making impedance measurements at multiple frequencies. A DDS (Direct Digital Synthesizer) stimulates the measurement circuit composed by the reference impedance and the unknown impedance. The voltage across the impedances is amplified by programmable gain instrumentation amplifiers and then digitized by analog to digital converters. To measure the impedance, a seven-parameter sine-fitting algorithm is used to estimate the sine signals across the impedances. The dsPIC is connected through RS-232 to a computer where the user can view the measurement results.
A Technique for Avoiding Connection Errors in Computerized Impedance-Measuring Systems
IEEE Transactions on Instrumentation and Measurement, 1971
The technique described uses a series of impedance measurements with different lead combinations and a calculation to determine the impedance of an unknown in the presence of lead and loading impedances. In general, a four-terminal ac or dc measurement requires four leads, four switches, and a series of five two-terminal measurements. However, an ac bridge is shown that requires only two switches and three measurements. The impedance of the swithces used to select the lead combinations has no effect on the measurement if it is constant and changes in switch resistance between closures can be avoided by choosing a measurement sequence that closes each switch only once. Most guarded four-terminal bridges are subject to errors caused by impedance to guard at the unknown end of the leads. A series of seven three-terminal measurements corrects for this type of error, which is particularly important for in situ measurements or for high-precision measurements on three-terminal standards. The technique is particularly applicable to an automatic computerized devide because two-terminal automatic bridges are substantially simpler than four-terminal bridges and because the speed of such a system and its computer can easily overcome the main disadvantages of the method???the necessity for several measurements and the calculation (which includes square roots). However, three two-terminal measurements and a simple calculation will measure a four-terminal impedance with a residual error that can be very small if the lead impedances are approximately equal. Thus the method may be practical for manual measurements as well.
Application of compensation techniques in a dsPIC based impedance measuring system
2011 IEEE EUROCON - International Conference on Computer as a Tool, 2011
A dsPIC (Digital Signal Peripheral Interface Controller) based impedance measuring system was developed and implemented. The system measures the impedance's amplitude and phase at the desired frequency using a sine-fitting algorithm running on the dsPIC and the results are sent to a personal computer using an USB or RS-232 connection. The measurement results are also shown in an LCD included in the device. This paper describes the system and details the OPEN and SHORT compensation techniques used to correct the measurements obtained with the device.
A multi-chanel electrical impedance meter based on digital lock-in technology
Pollack Periodica, 2019
The presented multichannel measuring system working on various frequencies is suitable either for electrical impedance spectroscopy or tomography. The authors of this paper have developed the complete measurement system and a graphical user interface platform. The accuracy of impedance amplitude and phase are 1 ppm and 0.01 o , respectively. The basic instrument works with 8 channels and can be expanded to 64 channels with the application of multiplexing or multiple parallel connected instruments in the same system.
In this paper, the measurement of impedances using analog to digital converters and ellipse fitting signal processing algorithms is described. The robustness of this new method makes it specially suited for low frequency impedance measurements (up to 1 MHz) in portable DSP based instruments. Previous methods relied on sine-fitting algorithms to estimate the sine parameters together with the signal frequency. These were iterative algorithms where convergence is not assured and they can be a significant computational burden requiring more processing capabilities in the instrument. With ellipse fitting, the frequency is not estimated and the algorithm is not iterative.
Embedded System for Impedance Measurement
2016
The purpose of this paper work is to design and implementation of an embedded system for impedance measurement. This system is design by using the impedance converter integrated circuit AD5933 which gives the real and imaginary value for measuring the impedance. The system combines an on-board frequency generator with build in 12-bit, 1 MSPS, analog-to-digital converter (ADC). There is built in frequency generator allows an external complex impedance to be excited with a known frequency. The response signal from the device testing under test (DUT) is sampled by the on-board ADC and a discrete Fourier transform (DFT) is processed by an onboard DSP engine. The DFT algorithm returns a real (R) and imaginary (I) data word at each output frequency as the real and imaginary register contents, which can be read from the serial I2C interface. The Arduino mega board microcontroller (ATmega2560) maintains control of the AD5933 via the I2C-compliant serial interface protocol. The impedance mea...