IEC TR 61340-1-1:2025

IEC TR 61340-1-1 ®
Edition 1.0 2025-05
TECHNICAL
REPORT
Electrostatics –
Part 1-1: Electrostatic phenomena – Measurement errors, uncertainties and
expression of results
ICS 17.220.99; 29.020 ISBN 978-2-8327-0389-2

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or
by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either
IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC copyright
or have an enquiry about obtaining additional rights to this publication, please contact the address below or your local
IEC member National Committee for further information.

IEC Secretariat Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - IEC Products & Services Portal - products.iec.ch
webstore.iec.ch/advsearchform Discover our powerful search engine and read freely all the
The advanced search enables to find IEC publications by a publications previews, graphical symbols and the glossary.
variety of criteria (reference number, text, technical With a subscription you will always have access to up to date
committee, …). It also gives information on projects, content tailored to your needs.
replaced and withdrawn publications.
Electropedia - www.electropedia.org
The world's leading online dictionary on electrotechnology,
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published containing more than 22 500 terminological entries in English
details all new publications released. Available online and and French, with equivalent terms in 25 additional languages.
once a month by email. Also known as the International Electrotechnical Vocabulary
(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc
If you wish to give us your feedback on this publication or
need further assistance, please contact the Customer
Service Centre: sales@iec.ch.
– 2 – IEC TR 61340-1-1:2025 © IEC 2025
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Measurement errors . 9
4.1 General . 9
4.2 Random error . 10
4.3 Systematic error. 10
4.4 Gross error . 10
5 Minimizing errors in practice . 11
5.1 Electrical resistance . 11
5.1.1 Test setup and procedures . 11
5.1.2 Contact resistance . 11
5.1.3 Leakage currents . 12
5.1.4 Voltage dependence . 12
5.1.5 Electrification . 13
5.1.6 Practical guidelines . 14
5.2 Electrostatic charge . 14
5.2.1 Electrometers and nanocoulomb meters . 14
5.2.2 Current integration method . 15
5.3 Electrostatic voltage. 15
5.3.1 General . 15
5.3.2 Electrometers . 15
5.3.3 Electrostatic voltmeters . 15
5.4 Electrostatic field . 16
5.5 ESD current . 17
5.6 Charge or voltage decay . 17
6 Measurement considerations . 19
6.1 Calibration and traceability . 19
6.2 Verification. 20
6.3 Laboratory services . 20
7 Uncertainty evaluation . 20
7.1 General . 20
7.2 Practical approach . 21
7.3 Evaluation of data . 21
7.3.1 General . 21
7.3.2 Combined uncertainty . 22
7.3.3 Confidence . 22
8 Expression of results . 23
8.1 General . 23
8.2 Significant digits . 23
8.3 Quantity units, symbols, and values . 24
8.4 Test report . 24
Bibliography . 27

Figure 1 – Distribution examples of different errors . 9
Figure 2 – Example of systematic error caused by contact resistance . 11
Figure 3 – Leakage currents (dashed lines) in different parts of the measurement
system . 12
Figure 4 – Examples of voltage dependencies . 12
Figure 5 – Capacitive loading . 13
Figure 6 – Voltage and electrostatic field measurement . 16
Figure 7 – Varying capacitance of charged plate can be an error source . 18
Figure 8 – Charge decay testing using a step response of electrostatic field . 18
Figure 9 – Calibration and traceability . 19

Table 1 – Examples of writing units and symbols . 24

– 4 – IEC TR 61340-1-1:2025 © IEC 2025
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROSTATICS –
Part 1-1: Electrostatic phenomena – Measurement errors,
uncertainties and expression of results

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as "IEC Publication(s)"). Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
may be required to implement this document. However, implementers are cautioned that this may not represent
the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC TR 61340-1-1 has been prepared by IEC technical committee 101: Electrostatics. It is a
Technical Report.
The text of this Technical Report is based on the following documents:
Draft Report on voting
101/728/DTR 101/735/RVDTR
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Report is English.

This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts in the IEC 61340 series, published under the general title Electrostatics, can
be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
– 6 – IEC TR 61340-1-1:2025 © IEC 2025
INTRODUCTION
Measurement in electrostatics poses unique challenges, often requiring the use of high
impedance measurement techniques. Electrostatic fields and potentials are challenging to
measure without disturbing the actual situation being observed. Additionally, materials used in
various applications can have very high electrical resistance above 1×10 Ω , complicating
measurements due to the low currents that are vulnerable to disturbances.
Electrostatic field meters, high impedance voltmeters and high resistance meters are often used
in compliance verification or qualification of electrostatic discharge (ESD) control items. Many
meters available in the market offer a user-friendly interface and a digital display, making them
easier to operate. However, it is important to note that a friendly user interface does not
guarantee accurate measurements without a proper understanding of the factors and sources
of errors that can influence the results.
It is important to know the basics of electrostatic theory so that measurement errors and
measurement uncertainties can be accurately evaluated. Measurements are incomplete without
consideration of error and uncertainty estimation, and this can lead to significant deviations in
conclusions.
This document provides practical guidance on how to understand and mitigate different types
of measurement errors and how to estimate measurement uncertainties when making
measurements according to the test methods of IEC 61340 series documents. This document
also includes examples of how to express the results.

ELECTROSTATICS –
Part 1-1: Electrostatic phenomena – Measurement errors,
uncertainties and expression of results

1 Scope
This part of IEC 61340 gives guidance on error consideration and uncertainty estimation in
electrostatics and ESD control measurements. It provides guidance on minimizing
measurement errors and estimating measurement uncertainties using practical methods. The
document also outlines how measurement results can be expressed in a test report. It is
important to note that this document serves as an informative guideline intended for individuals
who already have a solid understanding of the basics of electrostatics theory and measurement
techniques.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
arithmetic mean
quantity representing the quantities in a finite set or in an interval for n quantities:
X ( xx++… x ) (1)
in12
n
Note 1 to entry: Other terms used for the arithmetic mean are average and mean value.
3.2
deviation
difference between a datum and some reference value
Note 1 to entry: Typically, the reference value is the mean of the data.
=
– 8 – IEC TR 61340-1-1:2025 © IEC 2025
3.3
geometric mean
quantity representing the quantities in a finite set or in an interval for n positive quantities:
n (2)
X x⋅ x⋅… x
( )
in12
3.4
indicated value
value of the measurand given directly by a measuring instrument on the basis of its calibration
curve
Note 1 to entry: The indicated value can be derived from the indication using the calibration curve.
3.5
influence quantity
quantity that, in a direct measurement, does not affect the quantity that is actually measured,
but affects the relation between the indication and the measurement result
Note 1 to entry: Influence quantities can originate from the measured system, the measuring equipment or the
environment. For example, in high-resistance measurements, an electrostatic field originating from the environment
can act as an influence quantity.
3.6
measurand
quantity representing the quantities in a finite set or in an interval
Note 1 to entry: In common language, measurand value is sometimes referred to as the true or actual value.
3.7
median
value in the middle of a data set
Note 1 to entry: For n real values not necessarily different from each other, median is a real number such that the
number of values less than it is equal to the number of values greater than it.
3.8
standard deviation
positive square root of the variance
3.9
variable
variable quantity
physical quantity the value of which is subject to change and can usually be measured
3.10
variance
experimental variance of observations
measure of dispersion equal to the sum of the squared deviations from the mean value divided
by the number of deviations minus 1:
n
1 2
S XX−
(3)
( )
∑ ik,
n−1
k=1
where X is the mean value of the items of observation and X is an individual observation
ik,
=
=
3.11
variation
variation due to an influence quantity
measuring instrument, or the values of a material measure, when an influence quantity
assumes, successively, two different values
4 Measurement errors
4.1 General
The objective of a measurement is to determine the value of the measurand. The measurement
begins with specification of the measurand, a suitable test method and test procedure [1] . In
the IEC 61340 series, these are typically supplied by the test method standards. Measurement
error refers to the discrepancy or difference between the measured value of a quantity and the
measurand value. It means that when measurements are made with an adequate resolution,
there will be variations that cause the measured value to differ from the measurand value we
are trying to determine. The measurand value remains unknown, and it can also vary, making
interpretation of the measurement complicated. In statistics, an error is not necessarily a
"mistake". Measurement error is a natural part of the measurement process, as it can arise due
to inappropriate selection, or limitations of the test method, environmental variables, human
error, or other sources of uncertainty. Minimizing measurement error is important to obtain
sufficiently accurate and reliable results. Variability is an inherent part of the results of
measurements and of the measurement process. Measurement errors can be classified as
random errors, systematic errors, and gross errors. The shooting target (the red and blue circles)
in Figure 1 represents the distribution of different classes of errors. The different types of errors
are explained in 4.2, 4.3 and 4.4.

a) Random error b) Systematic error c) Gross error

Figure 1 – Distribution examples of different errors
Electrostatic measurements are sometimes seen as indicative only due to the presence of
excessive measurement errors. However, when these measurements are utilized to qualify or
accept ESD control items, error considerations and uncertainty estimation become crucial,
particularly if the result slightly exceeds the required limits. In such situations, it is imperative
to identify and address measurement errors. Ignoring errors can result in undesirable
consequences. As an example, a floor found to be out of specification can lead to expensive
remedial action or replacement.
___________
Numbers in square brackets refer to the Bibliography.

– 10 – IEC TR 61340-1-1:2025 © IEC 2025
4.2 Random error
Random errors are not systematic and do not consistently result in one direction. Instead, they
cause individual measurements to deviate randomly from the measurand value. These errors
can be positive or negative, resulting in measurements that are both higher and lower than the
measurand value. Random errors are typically caused by instrumentation or external influences
on instruments.
Random errors can be evaluated relatively easily by repeating the measurement until a
sufficient confidence is achieved. Variance and standard deviation can be calculated to show
statistical uncertainty. In electrostatic measurements, there is typically a significant variation
between the results compared to the accuracy of the instruments used. For instance, when
measuring high resistances of ESD control items made of non-metals, there can be a substantial
deviation of magnitudes due to variations in contact resistance. A metal-to-metal connection
can also lead to significant variations.
As a practical guideline, a test based on only one measurement is not reliable in electrostatics
and ESD control measurements. When the measurement is repeated at the same location of
the sample, the variation can be expected to be smaller than in different locations. When
different samples are measured, the higher variation can be expected. ESD control materials
can have significant variation that can be difficult to distinguish from experimental errors.
4.3 Systematic error
Systematic error refers to a consistent deviation or bias in the measurement or observation
process that affects the accuracy and precision of the results. It occurs consistently in the same
direction, either overestimating or underestimating the measurand value. Unlike random errors,
systematic errors cannot be reduced by averaging or increasing the number of measurements.
They are often caused by an inappropriate experimental design, calibration issues, or limitations
in the measuring instruments. External influences can also result in systematic errors. To
minimize systematic errors in electrostatic measurements, it is important to identify and address
their underlying causes. Systematic errors can be evaluated by conducting different test
methods. To ensure accurate evaluation, it is crucial to understand the relationship between
these methods. Systematic errors due to measuring instruments can also be evaluated by
conducting measurements on samples with known, accepted properties, provided that the
influence of instrumentation on different samples is known.
4.4 Gross error
Gross errors are significant mistakes or discrepancies in data that occur due to human error,
inappropriate test method, equipment malfunction, or procedural errors. They are typically large
deviations from the measurand values and can severely impact the accuracy of measurements
or observations. Gross errors can arise from mistakes in recording data, misreading, incorrect
calculations, incorrect test setup, unidentified influencing factors, inappropriate or faulty test
equipment. Identifying and eliminating gross errors is crucial to ensure the integrity and
reliability of data.
Gross errors in electrostatics and ESD control measurements are often caused by lack of
knowledge and misunderstanding. A user-friendly interface of instrumentation can create false
impression that measurement can be conducted without the need for theoretical understanding
or awareness of the variables influencing the results. This oversight can result in significant
errors. It is important to recognize the complexity inherent in electrostatics and ESD control
measurements, ensuring that the level of complexity is not underestimated, thus mitigating the
occurrence of errors.
Gross errors are not always easy to detect. For example, an "out of range" high resistance
reading in a floor resistance measurement could be a genuine result of correct measurement,
or it could indicate a faulty connection in the test set up.

As a general guideline, conducting electrostatics and ESD control measurements requires a
more focused understanding of specific measurement techniques beyond what electricians or
technicians typically learn in school. Understanding Ohm's law and Kirchoff's current and
voltage laws does not always suffice for making reliable measurements of very low currents,
high resistances, electrostatic charges, fields, and potentials without disturbing the original
state. Specialized knowledge in these areas is important for obtaining reliable measurements
and conclusions.
It is crucial to recognize that even professionals can make mistakes under challenging
circumstances. Mistakes are often caused by factors such as lack of concentration or rushing
through the measurement process. It is advisable to avoid incentives that prioritize lead times
in metrology. Placing excessive emphasis on speed can compromise the accuracy and reliability
of measurements.
5 Minimizing errors in practice
5.1 Electrical resistance
5.1.1 Test setup and procedures
One of the most common errors in resistance measurements is a failed test setup. For example,
it is possible that the reference ground point is not properly connected to earth, or there can be
excessive resistance in the ground path during resistance-to-ground measurements. In the real
world, there is no such thing as a "perfect ground". Ground currents, potentials, and disturbing
signals can be coupled to grounding wires at different frequencies. In a site assessment, the
resistance from the reference point, such as the protective earth (PE) or functional ground, can
be cross-checked with the metal structures of the building or other equipment ground bonding
points. Missing or inadequate grounding can result in gross errors.
Measurement wires can result in undesired coupling of disturbance to the high resistance
measurements. As a general guideline, short wires with insulation resistance at least an order
of magnitude greater than the expected resistance are used to prevent leakage and disturbance.
Electric shielding can be used to prevent coupling of disturbances.
5.1.2 Contact resistance
Contact resistance between the measurement electrode and the object under test in resistance
measurements can cause random errors, and it can also be a significant underlying cause of
systematic errors as shown in Figure 2.

Figure 2 – Example of systematic error caused by contact resistance
As a general guideline, an observation based on only one type of electrode is not always reliable
in electrostatics and ESD control measurements. The contact material causing the highest error
with one material under test can cause the lowest error with another material, and vice versa.
In humidity below 20 % rh, the systematic error in measurements of non-metals is typically
higher than the measurand. The contact error is case specific, and the evaluation is done when
required limits are exceeded.
To evaluate and address contact errors, the same electrode can be used with various contact
materials, checking each one first by making measurements on a flat metal plate. When making
measurements on a flat metal plate, an adequate indicated value is at least an order of
magnitude less than measurand value.

– 12 – IEC TR 61340-1-1:2025 © IEC 2025
5.1.3 Leakage currents
Another common root cause of gross error in resistance measurements is a leakage current.
Leakage can occur inside instrumentation or in a test fixture or between measurement wires as
shown in Figure 3. As a general guideline, short wires with insulation resistance at least an
order of magnitude greater than the expected resistance of the item under test are used.
Leakage can be detected by measuring the test setup without a connection to the item.
Out-of-scale indications are recorded both before and after connecting and measuring the
object.
Figure 3 – Leakage currents (dashed lines) in different parts of
the measurement system
A common source of error for the unwary operator can be a parallel leakage path established
through their body if they hold an electrode during the measurement, especially if their body is
earthed.
In on-site measurements, leakage currents of powered equipment can also cause errors.
5.1.4 Voltage dependence
Test voltages are specified in standard test methods, but it can be important to clarify the
voltage dependence, especially if the required resistance limit is exceeded. In many cases, this
dependence is not linear, which can have an impact on the conclusions. Figure 4 illustrates
different voltage dependence curves obtained from measurements taken at various locations
on the same flooring.
Figure 4 – Examples of voltage dependencies

5.1.5 Electrification
Measured resistance often varies as a function of measurement time, especially with high
resistance materials. As the voltage is applied for a longer duration, the measured current
usually decreases (and the resistance increases) because the test system and item under test
continue to charge exponentially. Polarisation of the material can also cause measured
resistance to increase. Ideally, resistance is recorded when the reading is constant. Typically,
electrification takes longer with high resistances due to the capacitive loading of the system.
Figure 5 shows a simplified circuit of the high resistance measurement. In this example R
represents the contact resistance between the electrode and sample. R is a resistance of the
sample in parallel with the capacitance (C) of the measurement setup. Thin multilayer samples
having high resistances typically result in long settling times due to the high capacitance
between layers.
Figure 5 – Capacitive loading
The procedure for determining electrification of the test system is described in IEC 61340-2-3
[2]. According to these instructions, the reading is taken when the displayed value has reached
a steady state. If the reading is within the tolerance range of the resistor, the procedure is
repeated five times while recording the required time for the instrument to indicate a steady-
state value. The average of the five recordings is the electrification time. It is important to note
that this procedure applies solely to the test fixture and completely disregards the electrification
behaviour of the material under test. If the capacitance and resistance of the test system are
known, the electrification time can be estimated by multiplying the time constant by five
(t = 5 × R × C). However, electrification depends on the material characteristics when exposed
E
to the electric field and power. Several variables, such as voltage, thickness, multilayer
structures, etc., affect electrification.
The electrification time in standard test methods of ESD control items is typically defined as
15 s. When comparing samples, it is always important to use the same electrification time.
However, 15 s is not always optimal time for all the material types and different dimensions of
the items under test. To understand the electrification behaviour and reliability of the
measurement with the tested item, the following test procedure (alternating polarity method)
can be applied:
• record the reading after 60 s electrification;
• change the polarity and record the reading again after 60 s;
• repeat the measurement several times with 60 s electrification by changing the polarity after
each recording;
• discard the first three readings;
• calculate the average and standard deviation of the results.
If the reading is not stable at 60 s, the material under test can be studied further even with
longer periods and different test voltages. Negative resistances can be seen when the electric
field of the material is pre-biased oppositely to the test voltage. In this case the reading will
increase to infinity and then starts to decrease close to the true resistance of the measurement
circuit at a certain voltage.
– 14 – IEC TR 61340-1-1:2025 © IEC 2025
5.1.6 Practical guidelines
The following guidelines can be used to avoid or mitigate errors in resistance measurements:
• Functional test – check the open circuit resistance (over scale indication) of test setup
before and after measurements.
• Functional test – check the short circuit resistance of test setup before and after
measurements.
• Performance verification – check the performance of resistance meter and test setup with
at least one known reference resistors before and after the measurement.
• Record the reading with sufficient electrification time – if possible, wait until the reading is
stable and record it with sufficient electrification time.
• A varying reading indicates unstable measurement – wait and change the polarity.
• Repeat the measurements until you can estimate the effect of random error.
• If the required limit is exceeded and if electrodes with different contact material are
available, consider repeating the measurement with these to evaluate systematic error.
• If you are following the standard test procedure without achieving confidence in the
measurement, make a statement of observations.
• If you have modified the test method or procedure to achieve confidence in results, note the
modifications used.
As a general guideline, if confidence of the measurement cannot be achieved, it is acceptable
to state that the resistance cannot be determined with the test method and state the reasons
why.
5.2 Electrostatic charge
5.2.1 Electrometers and nanocoulomb meters
Electrometers and charge meters generally have an accurately known integrating capacitor,
that is often placed in the feedback loop of an amplifier so that the voltage is proportional to the
integral of the input current. Charge is transferred through a current limiting resistor. The
voltage is scaled and displayed as charge.
The most important error sources in integrating capacitor measurements are stray fields,
leakage currents of the capacitor and test arrangement, amplifier input bias current and offset.
In addition, air ions, unknown voltage sources and electromotive forces can also cause
continuous current flow in low scale measurements. Depending on the series resistance,
integration time is typically more than a million times longer than in ESD current measurements
[3].
ESD is a high frequency phenomenon that cannot always be assessed with slow measurement
techniques. In a risk assessment it is important to recognize that the quasi-static source
parameters are not necessarily the same as the source parameters of ESD.
The following guidelines can be used to avoid or mitigate errors in charge measurements:
• Use cables as short as practically possible and an insulating, shielded measurement probe.
• Functional test – before the measurements, evaluate the measurement performance of test
setup by recording the rate of change of charge dQ/dt of the open circuit with the lowest
range.
• Record the result without the delay.
• Functional test – continue the measurement and record dQ/dt after recording the results.
• Functional test – check system operation with a known charge source (e.g., capacitor
charged to known voltage).
Most generic measurement errors can be avoided by following the reading of the electrometer
or charge meter carefully during the measurement. A varying reading indicates unstable
measurement.
5.2.2 Current integration method
A current integration method can be used with fast or slow charge transfers including ESD
current measurements using an oscilloscope and current probe. Some oscilloscopes have a
current integration function for easy access for the cumulative charge information. Otherwise,
the current waveform can be stored and exported for analysis in a spreadsheet or other
computer program.
The following sources of uncertainties are considered in fast measurements: bandwidth of the
oscilloscope and the current probe, sampling rate and capacitive coupling. Vertical resolution
is sufficient for integration of long charge transfers. The offset can be compensated to prevent
the cumulative effect on integration. Horizontal accuracy is typically less relevant and therefore
it can be ignored in uncertainty estimation.
Error sources of ESD current measurements are shown in 5.5. As a practical guideline, fast
transients can be slowed down to the adequate measurement bandwidth by inserting additional
inductance (wire) in the discharge path [3]. The method can be used for the charge
measurements when the associated distortion of the waveform can be tolerated.
5.3 Electrostatic voltage
5.3.1 General
Electrostatic voltage is generally measured with electrometers, electrostatic field meters, non-
contact voltmeters or high impedance contact voltmeters. Each of these techniques have pros
and cons. Surrounding electrostatic fields and the shape and size of the object under test that
can vary from the calibration situation are general sources of errors.
5.3.2 Electrometers
The most common uncertainty factors are bias current, probe capacitance and leakage currents
that typically cause voltage drop of the item under test. The leakage error can be evaluated by
recording dV/dt.
5.3.3 Electrostatic voltmeters
Electrostatic field meters are often used as a non-contact voltmeter. See 5.4.
DC-feedback probes have less significant effect on the measurement than electrostatic field
meters, provided the area of the item under test is large enough to detect electric potential
correctly. These meters are generally accurate at short measurement distances, but they can
have interference and balance issues especially when fast response is needed.
AC-feedback type of non-contact voltmeters are adequate for measuring conductive objects
when capacitance between the item and ground is higher than the capacitance between the
probe and the item. AC feedback meters are not sensitive to the measurement distance, but
they can result in significant errors with insulating materials and small objects due to the low
capacitance.
High impedance contact voltmeters can be used for measurements of small conductive or
dissipative objects. Insulative samples would not give a constant reading as the surface voltage
of an insulator is not uniform or constant. Very low input capacitance makes the instrument
sensitive to noise. Response times with relatively low values can also be an issue.

– 16 – IEC TR 61340-1-1:2025 © IEC 2025
5.4 Electrostatic field
Electrostatic field meters are generally used to measure the electrostatic field arising from
charged items and can also be used to estimate the surface voltage of the item. Some meters
are intended to be used as non-contact voltmeters and are calibrated to show the voltage of a
metal plate at a known, fixed distance (e.g. 25,4 mm or 100 mm) without a guard plate as shown
on the left in Figure 6. Other meters are typically calibrated in a homogeneous field with a guard
plate as shown on the right in Figure 6. Some of these meters also have surface voltage
measurement functions calibrated at specific distances.
When electrostatic field meters are used to assess electrostatic fields instead of surface voltage,
it is important to note that most of the meters require a reference that is typically ground. When
a grounded meter is brought to the electrostatic field, it distorts and increases the field. The
closer to the source the meter is, the higher is the field. In addition, the meter changes the
capacitance of the object, which can cause voltage and field suppression. Therefore, the
measurement arrangement changes the previously existing field. Electrostatic field meters have
V/m or V/in scales. A conversion from inch to meter or vice versa can be used. Ignoring or
mixing the units can result in gross error.
Electrostatic field meters calibrated as voltmeters typically only read surface voltage correctly
if the item under test is the same as in the calibration arrangement. If the item has a different
size or shape, the voltage reading will be affected. Readings are typically significantly reduced
with small objects or if the distance is greater than the calibration distance.

Figure 6 – Voltage and electrostatic field measurement
Surrounding objects, stray fields, capacitance and dimensions of the object to be measured, all
affect the measurement result. As a practical guideline, results of field measurements can
generally be considered indicative only.
For best results, these meters can have their readings corrected or be recalibrated with an
object similar to the intended measurement arrangement.
Typical human errors in electrostatic field measurements:
• electrostatic field and voltage measurements are misunderstood;
• operator and field meter are not connected to ground;
• measurement distance is not considered;
• the measurement scale (V/in or V/m) is ignored or mixed;
• stray fields are not considered;

• electrostatic field is mistakenly measured with a removable ion balance plate or charged
plate without intention to measure ion balance or charge decay.
5.5 ESD current
Where the ESD current waveform is deemed important, the limited bandwidth of a current probe,
oscilloscope and other system components compared to the fast transient waveform can result
in parameters su
...