High Performance Dielectric,
Conductivity and Electrochemical
Impedance Analyzers
Concepts
FeaturesPrinciples of Operation
Application Examples
Introduction
Novocontrol spectrometers fordielectric, conductivity and impedancematerial analysis have a world­wide
reputation for highest quality and flex­
ibility. Several systems for frequencies
from µHz up to GHz are available.
Sample cells are offered in standard
parallel plate transmission and reflec­tion geometry, four wire contact ar­rangement and as interdigit comb
electrodes. This allows characteriza­tion of solid materials, liquids, powders
and thin films. Several temperature
control systems covering a range from­160°C ‒ 1600°C are available. Withina modular concept, several imped­
ance analysis systems can be com­bined with each temperature control

Fig.1: The Active Sample Cell Test Interface (ZGS) converts the sample current
and voltage into two voltage signals, providing access to the sample impedance
which is converted to complex permittivity or conductivity. All system functions arecontrolled by the Alpha­A mainframe via high level GPIB commands and thus caneasily be integrated in self­written programs. Optional turn key operation, includ­ing data evaluation, visualization and data export, is provided by Novocontrol DE­
TACHEM/WinFIT software.

system and most of the sample cells.
Automatic system and experimentcontrol and sophisticated data evalu­
ation is performed by WinDETA andWinFIT software packages which haveestablished a world­wide standard indielectric, conductivity and impedancematerial analysis.

New approach to material
analysis
In the frequency range from 3 µHz
to 40 MHz, the Novocontrol Alpha andBeta analyzer series are used as thebase spectrometer component whichmeasures complex impedance of asample material prepared between
two ore more electrodes. The instru­
ments can be used as general pur­pose precision impedance analyzers
as well, but are especially designed
for dielectric, conductivity, and electro­

Fig. 2: Principles of impedance and material measurement1Alpha­A, Alpha, and Beta Analyzers

Novocontrol Technologies

chemical impedance material spectro­
scopy.

Alpha and Beta series
The single­unit Alpha and Beta ana­lyzers combine a series of exceptionalfeatures like ultra wide impedance
range, frequency range and high ac­
curacy in a fully automated and easy
to use instrument. These systems rep­resent a milestone in economical highperformance instrumentation. The
Beta analyzer has the same function­ality as the Alpha analyzer, but has ad­
ditional high impedance differential
voltage inputs for three­ or four­elec­
trode measurements as indicated inFigure 3 and Table 1.

Alpha­A modular series
The exceptional performance of theAlpha and Beta analyzers is extended
by the more recent Alpha­A modularseries with additional functionality
like, e.g., extended voltage and cur­rent ranges, fast measurement rates
and dc measurement functionality, in­cluding potentiostat and galvanostat
control functions. As these featuresare, for both technical and economical
Function
Dielectric Spectroscopy
Conductivity Spectroscopy
Impedance Spectroscopy

Fig. 3: Basic system set­up for Alpha­A, Alpha and Beta analyzers. For further
details, see text.
reasons, difficult to implement in asingle instrument, the Alpha­A system
consists of an Alpha­A mainframe unit
Alpha­AAlpha

Betawith additional test interfaces

××

Gain­Phase Measurements

××

Test Interface Support
Three­ and four­electrodeconfigurations

with ZG4 and POT/GALtest interfacesNon­linear Spectroscopy
Active Sample Cell specified atthe electrodes
High voltage

×××××

with option B

with option B

with ZGS testinterface
with HVB 300, HVB
1000, HVB 4000

High current

with POT/GAL 30 V­
2A and POT/GAL 15
V­10 A

Potentiostat function
Galvanostat function

with POT/GAL 30 V­
2A and POT/GAL 15
V­10 A

Fast measurements up to 150 points/s

with mainframe option F

dc bias option

with option B

Tab. 1: Functions of the Alpha­A, Alpha and Beta analyzer series.

2

which can be connected to a seriesof test interfaces (one at at time),
controlled by the mainframe. At least
one test interface is required in orderto perform an impedance measure­
ment.

Alpha­A versus Alpha andBeta series
The Alpha­A is the successor of
the Alpha and Beta analyzers which
are still available as economical al­
ternatives. The Alpha­A system not
only provides all functions alreadypresent in the Alpha and Beta series
analyzers, but additionally supports alarge selection of test interfaces. As aconsequence, the Alpha­A series is
our most powerful and flexible sys­
tem and thus the recommended solu­
tion for all new instrument designs.
Basic features of all three analyzer
series are listed in Table 1.
In the following, we will concen­
trate on the common features andtechnical principles of the Alpha­A,Alpha and Beta series only. The par­

Alpha­A, Alpha, and Beta Analyzers

Novocontrol Technologies

Fig. 4: PVDF results, 3D representation of permittivity, 2D diagrams for measured capacity and loss factor tanδ.

ticular functions of the Alpha­A test in­
terfaces and the modular concept aredescribed in the Novocontrol technicalbrochure "Test Interfaces for the Al­
pha­A Modular Measurement Sys­
tem".

Characterization of low loss
dielectrics
Due to the extraordinary high upper
impedance limit beyond 1014 Ω, nearly
all kinds of dielectrics and isolators
can be characterized even down tovery low frequencies, i.e., below themHz range. The high accuracy in loss
factor tan δ < 3.10­5 (resolution < 10­5)provides access to material properties
previously not accessible. Even low­est­loss materials used in ceramic ca­
pacitors, isolators in power industry or
weakest molecular relaxations can beanalyzed over an extremely wide fre­quency range.

configuration.

No limitations: High and low
conductive materials

Capacities down to 1 fF

In contrast to other systems fordielectric spectroscopy, the Alpha­A,
Alpha and Beta analyzers are by nomeans limited to high­impedance
dielectric samples. On the contrary:
the lower impedance limit of 0.01 Ω(0.0001 Ω for four­wire configurations)allows also to analyze conductive
samples like semiconductors, electro­
lytes and electrochemical systems
equally well. As the complete imped­
ance range of 16 orders of magnitudeis accessible, even samples exhibiting
drastic changes of impedance withtemperature or other external settings(e.g., temperature­induced metal­in­sulator­transitions) can be fully char­acterized in one single device

3

The combination of ultra­wide im­pedance range and broadband highaccuracy results in an exceptionallybroad capacity range as well. With
most impedance or dielectric analyz­
ers, small capacities in the pF range
or even below are usually hardly ac­
cessible if at all.
The Alpha­A, Alpha or Beta analyz­
ers, however, are specified to meas­
ure capacities as low as 1 fF
(0.001 pF) within 10 Hz ‒ 500 kHz.
Applications are, e.g., broadband
characterizations of small crystals,
measurements of stray capacities or
impedance of ill­defined electrodegeometries like, e.g., two needle elec­
trodes separated by 1 cm sample ma­
terial.

Alpha­A, Alpha, and Beta Analyzers

Novocontrol Technologies

Fig. 5: Dielectric properties of a 2 MHz quartz crystal, half power bandwidth: 30 Hz; 5 Hz and 0.1 Hz frequency
resolution for the left and right diagram, respectively.

Specified at the sample posi­tion
In the Alpha­A in combination with aZGS active sample cell test interface,
the impedance converter is directly
mounted on top of the sample cellconnected by rigid lines. This set­up
guarantees high accuracy up to40 MHz and provides optional controlof sample temperature. The accuracy
specification for material measure­ments applies to the sample position,offering a highly accurate turnkey
solution without calibration errors due
to cable inductance, contacts, straycapacities, grounding and shielding.

Innovative technology
The Alpha­A, Alpha and Beta ana­lyzers are based on state of the art di­gital signal processing techniques.
Automatic device control including selfcalibration is provided by the Novo­
control Windows software WinDETA.
As shown in fig. 2, the basic opera­tion is to create a sine wave at the fre­quency of interest, apply it to thesample and measure the sample
voltage U(t) and result current I(t).
From this, the amplitude I0 and phaseangle φ of the current harmonic basewave component I*(ω) is calculated bycomplex Fourier transform (FT) of I(t).
In addition to the phase detection, theFT suppresses all frequency compon­
ents in I(t) except a narrow band
centred around the generator fre­quency. This improves accuracy andreduces noise and DC drifts by sever­al orders of magnitude. E.g. measur­
ing a signal covered by a noise signalof 1000 times larger is possible. Fi­
nally, the impedance Z(ω) and materi­al parameters ε*(ω) and σ*(ω) arecalculated.

Digital signal synthesis
Such kind of set­up is implementedin the Alpha series as shown in Figure.
3. The optional high impedance differ­ential input amplifier is only included inthe Beta series. For the Alpha­Aseries, Fig. 3 has to be separated intwo parts. The lower part includes thefrequency response analyzer portion
from the two input channels down to
the signal processor. The upper partwith the impedance converter, refer­ence capacitors, differential input
amplifier and additional not shown
components are realized within sever­al test interfaces. For details, cf.
Table 1 and the Novocontrol technicalbrochure "Test Interfaces for Alpha­A
Modular Measurement System".
As shown in Fig. 3, a digital signal
processing system is used for both
frequency generation and analysis of
the input signals. The generator signal
is directly digitally synthesized overthe entire frequency range. At at rateof 400 MHz, the signal processor con­tinuously calculates digital sine wave
values which are transformed into asine wave voltage. This is done by ahigh speed digital analog converter(DAC) followed by a higher harmonicfilter. This kind of signal generation
4guarantees highest stability and a fre­quency resolution of 32 bit corres­
ponding to, e.g., 10 mHz out of40 MHz.

Digital signal analysis
The voltages from two independent
input channels are amplified, filteredand converted into two digital data
streams; these are analyzed online
with respect to their harmonic basewaves by discrete Fourier transform(DFT) in a phase­sensitive manner.
Channel 1 measures the voltage ap­
plied to the sample (V1). The resulting
sample current Is is transformed by theprecision impedance converter into
the voltage V2 measured by chan­nel 2.

Reference technique
Major parts of the signal generation
and analysis are performed in the di­gital system area. Phase and stability
errors are minimized to negligible val­ues. In order to reach similar high ac­
curacy in the analog systemcomponents as well, all Novocontrol
Technologies analyzers apply a partic­
ular reference technique: after eachmeasured impedance point, thesample is disconnected, and a preci­sion low­loss reference capacitor ismeasured under the same conditions.
The results of the reference measure­ment are used to eliminate all linear
systematic deviations. This techno­
logy, in combination with a straightfor­
ward digital design, provides the highAlpha­A, Alpha, and Beta Analyzers

Novocontrol Technologies

accuracy required for material analysis
and, in particular, spectroscopy of low­
loss dielectrics.

Measurement examples
The performance for low­loss mater­
ials is shown and discussed in thefollowing article. The measurements inFigs. 4 and 5 were performed using anAlpha­A analyzer with active sample
cell test interface ZGS and a Quatro
Cryosystem for temperature control. Inorder to demonstrate the overall sys­
tem performance, PVDF [1] waschosen as a material with moderateloss. Figure 4 shows the dielectric
spectrum for frequencies from 1 mHz
to 10 MHz at several temperatures.
PVDF shows α and β relaxations withlosses (tan δ) in the range from 0.01
to 0.2. At higher temperatures, the dc
conductivity creates a low frequency
increase of ε''. As shown in the three­dimensional diagrams, the data canbe measured over the entire fre­quency and temperature range nearly
without artefacts. In order to show theresults in more detail, the diagrams forcapacity Cp' and tan δ were confinedto the range of interest.
As a demonstration of the frequency
resolution and stability, a commercial
high Q quartz crystal. The samples
was mounted in the ZGS active
sample cell; measurements wereperformed at a stabilized temperatureof 20.00 °C ± 0.01 °C. Figure 5 shows
the dielectric properties with the typic­
al resonant behaviour. The resonancefrequency f0 is at 1999871.8 Hz with ahalf power width of 30 Hz. Below f0,
the device behaves like a 22 pF capa­
citor with ­90° phase shift. With in­creasing frequency, the real part ofcapacity, Cp', and the phase shift in­creases as well. At f0, the impedance
becomes purely resistive, indicated byvanishing Cp' and phase shift. Abovef0, the impedance changes to induct­ive behaviour corresponding to 90°
phase shift and a corresponding neg­
ative Cp'. As shown in Fig. 5, even at
0.1 Hz resolution the measurements
are free of any artefacts and noise. ItFig. 1: tan δ of an air capacitor (thickness: 50 µm, diameter: 30 mm) at different
temperatures measured Alpha Dielectric Analyzer (solid squares) and the
combination Broadband Dielectric Converter BDC + frequency response analyzer(open circles)
should be emphasized that each data
point is independently measured
without averaging or correlation toneighbouring points. Moreover, there
is no synchronization between thesample crystal and the Alpha internal
oscillator.

References
PVDF samples were supplied by Elf
Atochem France, Materials ResearchLab., Dr. B. Ernst, 27470 Serquigny,
FranceDr. Gerhard Schaumburg
Dr. Dirk Wilmer
Novocontrol Technologies GmbH &Co. KG

5Broadband DielectricMeasurement Tech­niques – Recent Pro­gress
High resolution measurements inthe frequency range from 10­4 Hz to107 Hz are based on frequency re­sponse analysis. This contribution
provides the measurement results of aperformance comparison of the Novo­
control Alpha High Resolution Dielec­
tric / Impedance Analyzer with a
combination of a Broadband Dielectric
Converter and a frequency responseanalyzer (BDC + FRA).
As a low loss test sample, an air ca­
pacitor mounted in the sample cell ofeach system was used. It was pre­pared from parallel gold plated elec­

Alpha­A, Alpha, and Beta Analyzers
trodes with 30 mm diameter. The elec­
trode distance was adjusted to 50 µmby two silica spacer rods resulting in
about 125 pF capacity.
Due to the conductance of the rods,
the capacitor shows especially at am­bient temperature remaining losses.
By cooling the capacitor to low tem­
peratures, the conductivity of thespacer rods decreases and the losses
are continuously reduced.
This kind of capacitor is well suitedfor testing the tan δ accuracy and res­olution of dielectric analysis systems.
Results for three different temperat­
ures are shown in Figure 1. At ­50 °C
and frequencies above 10 Hz, the ca­
pacitor losses are approx. tan δ» 10­4.
At lower frequencies, tan δ increases
to about 3ꞏ10­4 at 0.1 Hz. This de­pendence can be measured without
significant noise by the Alpha analyzer
at frequencies below 100 kHz. The
combination BDC + FRA shows thesame dependency, but superimposedby about 100 % noise due to the sys­
tem resolution limit tan δ of 10­4 which
is of the same order as the sample
loss.
If the temperature is lowered to­100 °C and ­140 °C, the capacitor
losses decrease further and the better
resolution limit of the Alpha analyzer isthe limiting factor as shown in thelower two diagrams of Figure 1. Com­
pared to the BDC + FRA combination,
the resolution is improved from 10­4 to10­5. At the high frequency end above
100 kHz, the results show an increasein tan δ which is not intrinsic to thesample, but due to high frequency lim­
itations for both systems. At 10 MHz,the accuracy is decreased to abouttan δ»0.01 corresponding to about 1°
phase accuracy.
Figure 2 shows similar measure­ments for a low loss polyethylene
sample at ambient temperature. The
sample capacity is about 160 pF andin good agreement for both systems.
The difference of about 1 % in the ab­solute value is due to stray capacities
and mounting deviations of the differ­

Novocontrol Technologies

Fig. 2: Capacitance Cp' and tan δ of a Polyethylene (PE) sample (thickness: 40µm, diameter: 20 mm) otherwise as Fig. 1.
ent sample cells. The tan δ of thesample is between 10­4 and 3ꞏ10­4.
The results of the two measurement
systems show the same behaviour asfor the low loss capacitor. Whereas for
the BDC + FRA combination thephase resolution limit is reached, theresults can be resolved with only 10 %scatter by the Alpha. The tan δ in­crease at high frequencies is again
due to internal limitations of both sys­tems. This limitation can be seen in
the capacity too. The deviations at
10 MHz are about 1.5 pF for the Alpha

6and about 8 pF for the BDC + FRA
combination.
Prof. Dr. Friedrich Kremer,
Universität Leipzig, Linnéstr.5,04103 Leipzig, Germany
The original text appeared in the No­
vocontrol Dielectrics Newsletter #11; itwas slightly modified for this issue.