A lot of engineering applications, from telecommunications to power systems, require

accurate measurement of phase angles. Some of them, like synchrophasor measurement and

calibration of instrument transformers with digital output, in order to reach high phase

measurement accuracy, require the knowledge of phase error of digitizers. Therefore, in this

paper a method for the measurement of digitizers’ absolute phase errors is proposed. It adopts a

sinewave and two square waves, that are the digitizer sample clock and a phase reference signal.

Combining the measurements of the relative phase differences between the adopted signals it is

possible to accurately evaluate the absolute phase error of a digitize

Crotti, G.

Delle Femine, A.

Gallo, D.

Giordano, D.

Landi, C.

Luiso, M.

Scaldarella, A.

English

A lot of engineering applications, from telecommunications to power systems, require accurate measurement of phase angles. Some of them, like synchrophasor measurement and calibration of instrument transformers with digital output, in order to reach high phase measurement accuracy, require the knowledge of phase error of digitizers. Therefore, in this paper a method for the measurement of digitizers' absolute phase errors is proposed. It adopts a sinewave and two square waves, that are the digitizer sample clock and a phase reference signal. Combining the measurements of the relative phase differences between the adopted signals it is possible to accurately evaluate the absolute phase error of a digitizer.The work reported here has received support from the EMPIR programme co-financed by the Participating States and from the European Union'

Crotti, Gabriella

Delle Femine, Antonio

Gallo, Daniele

Giordano, Domenico

Landi, Carmine

Luiso, Mario

Scaldarella, Ascanio

NEUROSURGERY ENTHUSIASTIC WOMEN SOCIETY

A Method for the Measurement of Digitizers' Absolute Phase Error

A lot of engineering applications, from telecommunications to power systems, require accurate measurement of phase angles. Some of them, like synchrophasor measurement and calibration of instrument transformers with digital output, in order to reach high phase measurement accuracy, require the knowledge of phase error of digitizers. Therefore, in this paper a method for the measurement of digitizers' absolute phase errors is proposed. It adopts a sinewave and two square waves, that are the digitizer sample clock and a phase reference signal. Combining the measurements of the relative phase differences between the adopted signals it is possible to accurately evaluate the absolute phase error of a digitizer

Archivio Istituzionale della Ricerca - Università degli Studi della Campania "Luigi Vanvitelli"

A lot of engineering applications, from telecommunications to power systems, require
accurate measurement of phase angles. Some of them, like synchrophasor measurement and
calibration of instrument transformers with digital output, in order to reach high phase
measurement accuracy, require the knowledge of phase error of digitizers. Therefore, in this
paper a method for the measurement of digitizers’ absolute phase errors is proposed. It adopts a
sinewave and two square waves, that are the digitizer sample clock and a phase reference signal.
Combining the measurements of the relative phase differences between the adopted signals it is
possible to accurately evaluate the absolute phase error of a digitize

METRICA Archivio istituzionale della ricerca - INRIM

Journal of Physics: Conference SeriesPAPER • OPEN ACCESSA Method for the Measurement of Digitizers’ Absolute Phase ErrorTo cite this article: G. Crotti et al 2018 J. Phys.: Conf. Ser. 1065 052035 View the article online for updates and enhancements.This content was downloaded from IP address 193.204.114.64 on 27/02/2019 at 12:40Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distributionof this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Published under licence by IOP Publishing LtdXXII World Congress of the International Measurement Confederation (IMEKO 2018)IOP Conf. Series: Journal of Physics: Conf. Series 1065 (2018) 052035IOP Publishingdoi:10.1088/1742-6596/1065/5/0520351      A Method for the Measurement of Digitizers’ Absolute Phase Error G. Crotti1, A. Delle Femine2, D. Gallo2, D. Giordano1, C. Landi2, M. Luiso2, A. Scaldarella2  1Istituto Nazionale di Ricerca Metrologica (INRIM), Torino, Italy 2Dept. of Engineering, University of Campania “Luigi Vanvitelli”, Aversa (CE), Italy  E-mail: mario.luiso@unicampania.it  Abstract. A lot of engineering applications, from telecommunications to power systems, require accurate measurement of phase angles. Some of them, like synchrophasor measurement and calibration of instrument transformers with digital output, in order to reach high phase measurement accuracy, require the knowledge of phase error of digitizers. Therefore, in this paper a method for the measurement of digitizers’ absolute phase errors is proposed. It adopts a sinewave and two square waves, that are the digitizer sample clock and a phase reference signal. Combining the measurements of the relative phase differences between the adopted signals it is possible to accurately evaluate the absolute phase error of a digitizer. 1. Introduction The knowledge of phase angles of signals is at the base of many engineering applications, from telecommunications to power systems ([1]-[5]). In particular, in most measurement applications, electronic instrumentation is based on digitizers, to convert analog signals to digital samples, and digital signal processors, to get the desired measurement value. However, every digitizer has its own phase frequency response which introduces a phase deviation between the analog input and its digital output samples. In some applications this phase deviation can be considered negligible, with respect to the measurand, and in others one could be interested only in the phase delay of two channels of the same digitizers, such as in energy or power measurement. Generally speaking, measuring the relative phase delay between two different channels of the same digitizer, or two channels of two different digitizers that have synchronized sampling clocks, is an issue solved in a number of scientific papers ([6]-[8]). However, there are special applications, such as Phasor Measurement Unit (PMU) ([9], [10]) or calibration of Low Power Instrument Transformers (LPIT) ([11]-[13]) with digital output (having as a reference an instrument transformer with analog output), where high phase accuracies, sometimes in the order of microradians, are required. In these situations, the absolute phase deviation of the single channel of the used digitizer may be comparable or higher than the required accuracy, introducing an unacceptable systematic error that highly influences the measurement result. An interesting technique for measurement of digitizer absolute phase error is proposed in [14], that involves the generation of a reference signal with known phase with respect to a time reference. In this paper, a technique for measuring the absolute phase errors of digitizer is presented. It is based on the preliminary characterization of the phase error of the used signal generator, through the use of a phase comparator ([6]-[7]). By means of a frequency counter, which measures the time delay between the sampling clock XXII World Congress of the International Measurement Confederation (IMEKO 2018)IOP Conf. Series: Journal of Physics: Conf. Series 1065 (2018) 052035IOP Publishingdoi:10.1088/1742-6596/1065/5/0520352      of the Digitizer Under Test (DUT) and a Phase Reference Signal (PRS), and applying the Discrete Fourier Transform (DFT) of the DUT samples, the absolute phase error of the DUT is measured. 2. Measurement method Let us suppose that the DUT is supplied with a sinusoidal signal 𝑠𝑔 generated by an arbitrary waveform generator (AWG) and to have available a square waveform, i.e. the PRS, with the same frequency of the sinusoidal signal, as it is illustrated in Figure 1. Assuming the rising edge of the PRS as the time reference (t = 0), the initial phase of the sine wave should be zero; however due to phase frequency response of the AWG and its internal time delay, the actual phase of the sine wave is 𝜑𝑔. Thus, the DUT input can be written as:  𝑠𝑔(𝑡) = sin(2𝜋𝑓0𝑡 + 𝜑𝑔(𝑓0)) (1)  where 𝑓0 is the signal frequency and, for sake of simplicity, a unitary amplitude is considered. Suppose that the DUT sampling clock, with period 𝑇𝑠, is nominally aligned with the PRS, but, due to the delay of the clock paths, it is actually delayed of a quantity 𝜏𝑐. Therefore, the samples at the output of the DUT can be expressed as:  𝑠𝐷𝑈𝑇(𝑘𝑇𝑠) = sin(2𝜋𝑓0(𝑘𝑇𝑠 + 𝜏𝑐) + 𝜑𝑔(𝑓0) + 𝜑𝐷𝑈𝑇(𝑓0)) (2)  where 𝜑𝐷𝑈𝑇(𝑓0) is the phase deviation introduced by the DUT at frequency 𝑓0 and the gain deviation has been neglected. The quantity 𝜑𝑔(𝑓0) can be measured with a phase comparator (COMP) ([1]) and the quantity 𝜏𝑐 can be measured with a frequency counter. The phase angle of the DUT samples ∠𝐹[𝑠𝐷𝑈𝑇(𝑘𝑇𝑠)]|𝑓0, at frequency 𝑓0, can be evaluated by performing the DFT; thus, the DUT phase error, at frequency 𝑓0, can be evaluated as:  𝜑𝐷𝑈𝑇(𝑓0) = ∠𝐹[𝑠𝐷𝑈𝑇(𝑘𝑇𝑠)]|𝑓0 −  2𝜋𝑓0𝜏𝑐 − 𝜑𝑔(𝑓0) (3)  3. Measurement setup and results To validate the proposed method a proper automated test bench has been realized. The system is based on a PXI chassis and the external universal frequency counter Agilent 53230A (350 MHz, 20 ps). The multifunction I/O module NI PXIe-6124 (+/- 10 V, 16 bit, maximum sampling rate of 4 MHz) has been used for DUT. The module NI PXI-5422 (+/- 12 V, programmable gain, 16 bit, maximum sampling rate of 200 MHz) has been used for AWG.  Figure 1. DUT sinusoidal input, Phase Reference Signal and ideal and actual samples acquired by DUT. XXII World Congress of the International Measurement Confederation (IMEKO 2018)IOP Conf. Series: Journal of Physics: Conf. Series 1065 (2018) 052035IOP Publishingdoi:10.1088/1742-6596/1065/5/0520353      The digitizer used for the phase comparator is, instead, the module NI PXI 4462 (+/- 10 V, 24 bit, maximum sampling rate of 204.8 kHz). Excluding the comparator, which operates asynchronously, all the instruments of the test bench use clocks generated by the NI PXI-6683H synchronization board, so they are all synchronous. In particular, the sampling frequency of the AWG is 5 MHz, while the sampling clock of the DUT is 1 MHz. The PRS is generated by the NI PXI-6683H, too. A digital storage oscilloscope (Tektronix TDS 2014B) is used to control the correct operation of the setup. The block diagram of the measurement setup is shown in Fig. 2, where CDUT is the DUT sampling clock and CAWG is the sampling clock of the AWG. The sine wave is connected to both the DUT and the COMP. The COMP measures the phase difference between the sine wave and the PRS. The frequency counter receives a 10 MHz clock as external timebase and measures the time delay between PRS and DUT sampling clock. All the clock and signal paths are symmetric in order to avoid different propagation delays. Since the two input channels of COMP and of the counter could have inter-channel time (or phase) delay, in order to compensate for these systematic errors, two measurements are performed, interchanging the signals between the two channels, both for COMP and counter ([1]). Measurement software is developed in LabVIEW. For each test point, amplitude and frequency of the test signal of the DUT can be chosen and 30 repeated measurements of ∠𝐹[𝑠𝐷𝑈𝑇(𝑘𝑇𝑠)]|𝑓0, 𝜏𝑐 and 𝜑𝑔(𝑓0) are performed. An automated test, sweeping frequency of the test signal from 50 Hz to 20 kHz, has been performed. Two amplitudes, 5 V and 10 V, and a constant DUT sampling frequency of 1 MHz have been chosen. Fig. 3 shows the DUT phase frequency responses, at 5 V and 10 V, where, for each point, mean value and standard deviation is plotted. It is worth noting that the DUT does not use antialiasing filter. Therefore, as expected, its phase error is linearly dependent on the input signal frequency and it is due to an almost constant time delay introduced by the digitizer in its bandwidth.   Fig. 2. Measurement setup.  Figure 3. DUT phase frequency response. XXII World Congress of the International Measurement Confederation (IMEKO 2018)IOP Conf. Series: Journal of Physics: Conf. Series 1065 (2018) 052035IOP Publishingdoi:10.1088/1742-6596/1065/5/0520354      4. Conclusion In this paper a new technique for the measurement of digitizers’ absolute phase error is presented. A commercial digitizer has been characterized changing input signal characteristics, i.e. amplitude and frequency. However, the technique is general and can be applied to evaluate the absolute phase error of every digitizer.  References [1] G. Aurilio, M. Balato, G. Graditi, C. Landi, M. Luiso, M. Vitelli, “Fast Hybrid MPPT Technique for Photovoltaic Applications: Numerical and Experimental Validation,” Advances in Power Electronics, vol. 2014, Article ID 125918, 15 pages, 2014. doi:10.1155/2014/125918, June 2014 [2] D. Gallo, R. Langella, M. Luiso, A. Testa and N. R. Watson, "A New Test Procedure to Measure Power Electronic Devices' Frequency Coupling Admittance," in IEEE Transactions on Instrumentation and Measurement. [3] G. Crotti, D. Giordano, M. Luiso and P. Pescetto, "Improvement of Agilent 3458A Performances in Wideband Complex Transfer Function Measurement," in IEEE Transactions on Instrumentation and Measurement, vol. 66, no. 6, pp. 1108-1116, June 2017. [4] G. Crotti, D. Gallo, D. Giordano, C. Landi and M. Luiso, "A Characterized Method for the Real-Time Compensation of Power System Measurement Transducers," in IEEE Transactions on Instrumentation and Measurement, vol. 64, no. 6, pp. 1398-1404, June 2015. [5] G. Crotti, D. Gallo, D. Giordano, C. Landi, M. Luiso, “FPGA-based real time compensation method for medium voltage transducers”, ACTA IMEKO, vol. Vol 4, p. 82-89, ISSN: 2221-870X, Year 2015 [6] B. Trinchera, D. Serazio, and U. Pogliano, “Asynchronous phase comparator for characterization of devices for pmus calibrator”, IEEE Transactions on Instrumentation and Measurement, 66(6):1139–1145, June 2017. [7] G. Crotti, D. Gallo, D. Giordano, C. Landi, and M. Luiso, “Industrial comparator for smart grid sensor calibration”, IEEE Sensors Journal, 17(23):7784–7793, Dec 2017. [8] E. Mohns, J. Meisner, G. Roeissle, and M. Seckelmann, “A wideband current transformer bridge”, IEEE Transactions on Instrumentation and Measurement, 63(10):2322–2329, Oct 2014. [9] P. Tosato, D. Macii, M. Luiso, D. Brunelli, D. Gallo and C. Landi, "A Tuned Lightweight Estimation Algorithm for Low-Cost Phasor Measurement Units," in IEEE Transactions on Instrumentation and Measurement, vol. 67, no. 5, pp. 1047-1057, May 2018. [10] D. Gallo, C. Landi, M. Luiso, P. Tosato, D. Macii, D. Brunelli, "A Testbed for the Experimental Characterization of Estimation Algorithms for Phasor Measurement Units" 2017 IEEE International Workshop on Applied Measurements for Power Systems (AMPS), Liverpool, United Kingdom, 2017, pp. 118-123.  [11] G. Crotti, D. Gallo, D. Giordano, C. Landi, M. Luiso, “Medium Voltage Divider Coupled With an Analog Optical Transmission System”, IEEE Transactions on Instrumentation and Measurement, vol. 63, p. 2349-2357, October 2014 [12] G. Crotti; D. Gallo; D. Giordano; C. Landi; M. Luiso; M. Modarres; M. Zucca, "Frequency Compliance of MV Voltage Sensors for Smart Grid Application," IEEE Sensors Journal, vol. 17, no. 23, pp. 7621-7629, Dec.1, 1 2017. doi: 10.1109/JSEN.2017.2726116 [13] G. Crotti; D. Gallo; D. Giordano; C. Landi; M. Luiso; M. Modarres, "Frequency Response of MV Voltage Transformer Under Actual Waveforms", IEEE Transactions on Instrumentation and Measurement, vol. 66, no. 6, pp. 1146-1154, June 2017, ISSN: 0018-9456, DOI: 10.1109/TIM.2017.2652638 [14] M. Acanski, G. Rietveld, and D. Hoogenboom, “Accurate phase calibration of pmus and pmu calibrators”, In 2016 Conference on Precision Electromagnetic Measurements (CPEM 2016), pages 1–2, July 2016. 

A Method for the Measurement of Digitizers’ Absolute Phase Error

CINECA IRIS Institutional Research Information System

Journal of Physics: Conference Series
PAPER • OPEN ACCESS
A Method for the Measurement of Digitizers’ Absolute Phase Error
To cite this article: G. Crotti et al 2018 J. Phys.: Conf. Ser. 1065 052035
 
View the article online for updates and enhancements.
This content was downloaded from IP address 193.204.114.64 on 27/02/2019 at 12:40
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution
of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Published under licence by IOP Publishing Ltd
XXII World Congress of the International Measurement Confederation (IMEKO 2018)
IOP Conf. Series: Journal of Physics: Conf. Series 1065 (2018) 052035
IOP Publishing
doi:10.1088/1742-6596/1065/5/052035
1
 
 
 
 
 
 
A Method for the Measurement of Digitizers’ Absolute Phase 
Error 
G. Crotti1, A. Delle Femine2, D. Gallo2, D. Giordano1, C. Landi2, M. Luiso2, A. 
Scaldarella2 
 
1Istituto Nazionale di Ricerca Metrologica (INRIM), Torino, Italy 
2Dept. of Engineering, University of Campania “Luigi Vanvitelli”, Aversa (CE), Italy 
 
E-mail: mario.luiso@unicampania.it 
 
Abstract. A lot of engineering applications, from telecommunications to power systems, require 
accurate measurement of phase angles. Some of them, like synchrophasor measurement and 
calibration of instrument transformers with digital output, in order to reach high phase 
measurement accuracy, require the knowledge of phase error of digitizers. Therefore, in this 
paper a method for the measurement of digitizers’ absolute phase errors is proposed. It adopts a 
sinewave and two square waves, that are the digitizer sample clock and a phase reference signal. 
Combining the measurements of the relative phase differences between the adopted signals it is 
possible to accurately evaluate the absolute phase error of a digitizer. 
1. Introduction 
The knowledge of phase angles of signals is at the base of many engineering applications, from 
telecommunications to power systems ([1]-[5]). In particular, in most measurement applications, 
electronic instrumentation is based on digitizers, to convert analog signals to digital samples, and digital 
signal processors, to get the desired measurement value. However, every digitizer has its own phase 
frequency response which introduces a phase deviation between the analog input and its digital output 
samples. In some applications this phase deviation can be considered negligible, with respect to the 
measurand, and in others one could be interested only in the phase delay of two channels of the same 
digitizers, such as in energy or power measurement. Generally speaking, measuring the relative phase 
delay between two different channels of the same digitizer, or two channels of two different digitizers 
that have synchronized sampling clocks, is an issue solved in a number of scientific papers ([6]-[8]). 
However, there are special applications, such as Phasor Measurement Unit (PMU) ([9], [10]) or 
calibration of Low Power Instrument Transformers (LPIT) ([11]-[13]) with digital output (having as a 
reference an instrument transformer with analog output), where high phase accuracies, sometimes in the 
order of microradians, are required. In these situations, the absolute phase deviation of the single channel 
of the used digitizer may be comparable or higher than the required accuracy, introducing an 
unacceptable systematic error that highly influences the measurement result. An interesting technique 
for measurement of digitizer absolute phase error is proposed in [14], that involves the generation of a 
reference signal with known phase with respect to a time reference. In this paper, a technique for 
measuring the absolute phase errors of digitizer is presented. It is based on the preliminary 
characterization of the phase error of the used signal generator, through the use of a phase comparator 
([6]-[7]). By means of a frequency counter, which measures the time delay between the sampling clock 
XXII World Congress of the International Measurement Confederation (IMEKO 2018)
IOP Conf. Series: Journal of Physics: Conf. Series 1065 (2018) 052035
IOP Publishing
doi:10.1088/1742-6596/1065/5/052035
2
 
 
 
 
 
 
of the Digitizer Under Test (DUT) and a Phase Reference Signal (PRS), and applying the Discrete 
Fourier Transform (DFT) of the DUT samples, the absolute phase error of the DUT is measured. 
2. Measurement method 
Let us suppose that the DUT is supplied with a sinusoidal signal 𝑠𝑔 generated by an arbitrary waveform 
generator (AWG) and to have available a square waveform, i.e. the PRS, with the same frequency of the 
sinusoidal signal, as it is illustrated in Figure 1. 
Assuming the rising edge of the PRS as the time reference (t = 0), the initial phase of the sine wave 
should be zero; however due to phase frequency response of the AWG and its internal time delay, the 
actual phase of the sine wave is 𝜑𝑔. Thus, the DUT input can be written as: 
 
𝑠𝑔(𝑡) = sin(2𝜋𝑓0𝑡 + 𝜑𝑔(𝑓0)) (1) 
 
where 𝑓0 is the signal frequency and, for sake of simplicity, a unitary amplitude is considered. Suppose 
that the DUT sampling clock, with period 𝑇𝑠, is nominally aligned with the PRS, but, due to the delay 
of the clock paths, it is actually delayed of a quantity 𝜏𝑐. Therefore, the samples at the output of the DUT 
can be expressed as: 
 
𝑠𝐷𝑈𝑇(𝑘𝑇𝑠) = sin(2𝜋𝑓0(𝑘𝑇𝑠 + 𝜏𝑐) + 𝜑𝑔(𝑓0) + 𝜑𝐷𝑈𝑇(𝑓0)) (2) 
 
where 𝜑𝐷𝑈𝑇(𝑓0) is the phase deviation introduced by the DUT at frequency 𝑓0 and the gain deviation has 
been neglected. The quantity 𝜑𝑔(𝑓0) can be measured with a phase comparator (COMP) ([1]) and the 
quantity 𝜏𝑐 can be measured with a frequency counter. The phase angle of the DUT samples 
∠𝐹[𝑠𝐷𝑈𝑇(𝑘𝑇𝑠)]|𝑓0, at frequency 𝑓0, can be evaluated by performing the DFT; thus, the DUT phase error, 
at frequency 𝑓0, can be evaluated as: 
 
𝜑𝐷𝑈𝑇(𝑓0) = ∠𝐹[𝑠𝐷𝑈𝑇(𝑘𝑇𝑠)]|𝑓0 −  2𝜋𝑓0𝜏𝑐 − 𝜑𝑔(𝑓0) (3) 
 
3. Measurement setup and results 
To validate the proposed method a proper automated test bench has been realized. The system is based 
on a PXI chassis and the external universal frequency counter Agilent 53230A (350 MHz, 20 ps). The 
multifunction I/O module NI PXIe-6124 (+/- 10 V, 16 bit, maximum sampling rate of 4 MHz) has been 
used for DUT. The module NI PXI-5422 (+/- 12 V, programmable gain, 16 bit, maximum sampling rate 
of 200 MHz) has been used for AWG. 
 
Figure 1. DUT sinusoidal input, Phase Reference Signal and ideal and actual samples acquired by 
DUT. 
XXII World Congress of the International Measurement Confederation (IMEKO 2018)
IOP Conf. Series: Journal of Physics: Conf. Series 1065 (2018) 052035
IOP Publishing
doi:10.1088/1742-6596/1065/5/052035
3
 
 
 
 
 
 
The digitizer used for the phase comparator is, instead, the module NI PXI 4462 (+/- 10 V, 24 bit, 
maximum sampling rate of 204.8 kHz). Excluding the comparator, which operates asynchronously, all 
the instruments of the test bench use clocks generated by the NI PXI-6683H synchronization board, so 
they are all synchronous. In particular, the sampling frequency of the AWG is 5 MHz, while the 
sampling clock of the DUT is 1 MHz. The PRS is generated by the NI PXI-6683H, too. A digital storage 
oscilloscope (Tektronix TDS 2014B) is used to control the correct operation of the setup. The block 
diagram of the measurement setup is shown in Fig. 2, where CDUT is the DUT sampling clock and CAWG 
is the sampling clock of the AWG. 
The sine wave is connected to both the DUT and the COMP. The COMP measures the phase difference 
between the sine wave and the PRS. The frequency counter receives a 10 MHz clock as external 
timebase and measures the time delay between PRS and DUT sampling clock. 
All the clock and signal paths are symmetric in order to avoid different propagation delays. Since the 
two input channels of COMP and of the counter could have inter-channel time (or phase) delay, in order 
to compensate for these systematic errors, two measurements are performed, interchanging the signals 
between the two channels, both for COMP and counter ([1]). 
Measurement software is developed in LabVIEW. For each test point, amplitude and frequency of the 
test signal of the DUT can be chosen and 30 repeated measurements of ∠𝐹[𝑠𝐷𝑈𝑇(𝑘𝑇𝑠)]|𝑓0, 𝜏𝑐 and 𝜑𝑔(𝑓0) 
are performed. 
An automated test, sweeping frequency of the test signal from 50 Hz to 20 kHz, has been performed. 
Two amplitudes, 5 V and 10 V, and a constant DUT sampling frequency of 1 MHz have been chosen. 
Fig. 3 shows the DUT phase frequency responses, at 5 V and 10 V, where, for each point, mean value 
and standard deviation is plotted. 
It is worth noting that the DUT does not use antialiasing filter. Therefore, as expected, its phase error is 
linearly dependent on the input signal frequency and it is due to an almost constant time delay introduced 
by the digitizer in its bandwidth. 
 
 
Fig. 2. Measurement setup. 
 
Figure 3. DUT phase frequency response. 
XXII World Congress of the International Measurement Confederation (IMEKO 2018)
IOP Conf. Series: Journal of Physics: Conf. Series 1065 (2018) 052035
IOP Publishing
doi:10.1088/1742-6596/1065/5/052035
4
 
 
 
 
 
 
4. Conclusion 
In this paper a new technique for the measurement of digitizers’ absolute phase error is presented. A 
commercial digitizer has been characterized changing input signal characteristics, i.e. amplitude and 
frequency. However, the technique is general and can be applied to evaluate the absolute phase error of 
every digitizer. 
 
References 
[1] G. Aurilio, M. Balato, G. Graditi, C. Landi, M. Luiso, M. Vitelli, “Fast Hybrid MPPT Technique 
for Photovoltaic Applications: Numerical and Experimental Validation,” Advances in Power 
Electronics, vol. 2014, Article ID 125918, 15 pages, 2014. doi:10.1155/2014/125918, June 2014 
[2] D. Gallo, R. Langella, M. Luiso, A. Testa and N. R. Watson, "A New Test Procedure to Measure 
Power Electronic Devices' Frequency Coupling Admittance," in IEEE Transactions on 
Instrumentation and Measurement. 
[3] G. Crotti, D. Giordano, M. Luiso and P. Pescetto, "Improvement of Agilent 3458A Performances 
in Wideband Complex Transfer Function Measurement," in IEEE Transactions on 
Instrumentation and Measurement, vol. 66, no. 6, pp. 1108-1116, June 2017. 
[4] G. Crotti, D. Gallo, D. Giordano, C. Landi and M. Luiso, "A Characterized Method for the Real-
Time Compensation of Power System Measurement Transducers," in IEEE Transactions on 
Instrumentation and Measurement, vol. 64, no. 6, pp. 1398-1404, June 2015. 
[5] G. Crotti, D. Gallo, D. Giordano, C. Landi, M. Luiso, “FPGA-based real time compensation 
method for medium voltage transducers”, ACTA IMEKO, vol. Vol 4, p. 82-89, ISSN: 2221-
870X, Year 2015 
[6] B. Trinchera, D. Serazio, and U. Pogliano, “Asynchronous phase comparator for characterization 
of devices for pmus calibrator”, IEEE Transactions on Instrumentation and Measurement, 
66(6):1139–1145, June 2017. 
[7] G. Crotti, D. Gallo, D. Giordano, C. Landi, and M. Luiso, “Industrial comparator for smart grid 
sensor calibration”, IEEE Sensors Journal, 17(23):7784–7793, Dec 2017. 
[8] E. Mohns, J. Meisner, G. Roeissle, and M. Seckelmann, “A wideband current transformer bridge”, 
IEEE Transactions on Instrumentation and Measurement, 63(10):2322–2329, Oct 2014. 
[9] P. Tosato, D. Macii, M. Luiso, D. Brunelli, D. Gallo and C. Landi, "A Tuned Lightweight 
Estimation Algorithm for Low-Cost Phasor Measurement Units," in IEEE Transactions on 
Instrumentation and Measurement, vol. 67, no. 5, pp. 1047-1057, May 2018. 
[10] D. Gallo, C. Landi, M. Luiso, P. Tosato, D. Macii, D. Brunelli, "A Testbed for the Experimental 
Characterization of Estimation Algorithms for Phasor Measurement Units" 2017 IEEE 
International Workshop on Applied Measurements for Power Systems (AMPS), Liverpool, 
United Kingdom, 2017, pp. 118-123.  
[11] G. Crotti, D. Gallo, D. Giordano, C. Landi, M. Luiso, “Medium Voltage Divider Coupled With 
an Analog Optical Transmission System”, IEEE Transactions on Instrumentation and 
Measurement, vol. 63, p. 2349-2357, October 2014 
[12] G. Crotti; D. Gallo; D. Giordano; C. Landi; M. Luiso; M. Modarres; M. Zucca, "Frequency 
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A Method for the Measurement of Digitizers’ Absolute Phase Error

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