Abstract
The paper presents a method for digital compensation of the ratio and phase angle errors of a resistive voltage divider. The system consists of a separate electrical circuit of a resistive divider, and a digital compensation system based on National Instruments (NI) PCI eXtension for Instrumentation (PXI) PXI-5922 digital acquisition cards (DAQ). A novel approach to the real-time compensation is presented, using digital signal processing. The algorithm is based on Wiener filtering and finite-impulse-response (FIR) filters. The proposed digital compensation, using FIR digital filtration and NI PXI DAQs, gives maximum magnitude error below 400 ppm and the phase angle error below 4500 μrad, in the frequency band 50 Hz–100 kHz. The algorithm allows the fine-tuning of the compensation to adjust to the possible change in the original transfer function due to the aging of the components.
Highlights
In this paper, we present digital compensation of a resistive voltage divider (RVD), developed for digital sampling wattmeter application
The compensated RVD consists of a separate electrical circuit, and a digital compensation system based on National Instruments PCI eXtension for Instrumentation (PXI)-5922 digital acquisition cards (DAQ)
The proposed digital compensation, using FIR digital filtration and National Instruments (NI) PXI DAQs, gives maximum magnitude error below 400 ppm and the phase angle error below 4500 μrad, in the frequency band 50 Hz–100 kHz. Those errors can mostly be attributed to the hardware and software limitations in the real-time implementation, while the proposed algorithm can mathematically fit the compensating transfer function with magnitude error below 40 ppm and overall phase angle error below 150 μrad, in the same frequency band
Summary
We present digital compensation of a resistive voltage divider (RVD), developed for digital sampling wattmeter application. This is a part of our current efforts in precise measurement of power in low frequency and radio frequency range [1,2]. While the frequencies in the power quality frequency range (e.g., below 3 kHz) are most important, frequencies needed or produced in electronic devices are constantly increasing, and many commercial power meters are declared by their manufacturers as being able to measure power up to MHz region [3]. The RVDs are sensitive to the load impedance, which is consisted of the cable impedance and the input impedance of the digital acquisition card (DAQ) or a digital multimeter (DMM).
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