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Here we discuss the sensitivity and accuracy of EMF or ELF measuring instruments used for performing electromagnetic field (EMF) or electro-magnetic radiation EMR measurements to measure EMF exposure levels in gauss or milligauss. We discusses sources of error and variation in EMF measurements and we review and make suggestions for using several low-cost EMF measurement devices to determine the instantaneous electromagnetic field exposure.

Because RF and EMF measurement tools need to be properly chosen to measure the particular type and frequency of RF or EMF signal that is of interest, be sure to also see EMF RF FIELD & FREQUENCY DEFINITIONS for a simple explanation of different types of radio frequency (RF) and electromagnetic frequency (EMF) types and where they are found. Also see Definitions of Gauss vs Milligauss for details about gauss and milligauss and definitions of these terms

See ENVIRO-SCARE, EMF & Property Values if you don't know what EMF, ELF, or electromagnetic fields are or if you want a summary of the possible health effects of EMF exposure and the more likely effect on the property value of homes located very close to power transmission lines. Readers who intend to make their own EMF measurements should be sure to also see WORKSHEET for EMF MEASUREMENTS and also WORKSHEET for EMF MEASUREMENTS - Example.

Also see Electric Power Lines, Electromagnetic Fields, Cancer Risk, & "Enviro-Scare" - The Normal Curve Cycle of Public Fear of Environmental Issues which discusses the impact of EMF and other environmental concerns on property values. And see EMF ELECTROMAGNETIC FIELDS & HUMAN EXPOSURE which discusses EMF exposure in the workplace.

© Copyright 2010 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

The information provided here is for research and study purposes. The author makes no representation of unique expertise on this topic, other than having field experience in EMF measurement, having studied technical literature and having conversed with other experts and authors in the field for a number of years.

Sensitivity & Accuracy of EMF Measuring Instruments

Most hand-held low-cost EMF measuring instruments (see our list at Evaluation of Low-Cost EMF Instruments) can make measurements down to 1 milligauss. Because it is common for us to find background EMF levels of 1-3 milligauss in residential neighborhoods where local electrical power distribution lines and transformers are present, and because some studies examined EMF field strengths down to this low level, a do-it-yourself EMF measurement project should probably avoid using instruments that lack that level of sensitivity.

But as we explain next, an accurate, sensitive EMF instrument is insufficient for making accurate and repeatable EMF measurements.

• Some instruments obtain EMF measurements that are sensitive to the orientation or position in which the instrument is held. Be sure to check that your instrument's readings are consistent regardless of instrument position, use a Tri-field instrument to avoid this source of inaccuracy, or if you prefer, as we do, to be able to see the field shape and source, be sure that your measurement procedure copes with this variation.
  
  We describe the position sensitivity problem in more detail at EMF Polarity & Shape Affect Measurements. We describe how to do so at Recommended EMF Measurement Procedure. We illustrate the EMF field shape at EMF/EMR Measurement Procedure Overview.
• EMF measurements are sensitive to distance from the source of the EMF. See Distance from the EMF Source Affects Strength.
  
• EMF measurements are sensitive to interference from local EMF sources that may swamp or distort EMF from a power transmission line. See   Local EMF Sources May Exceed Power Line Strength for details.
• EMF measurements are highly sensitive to hourly and seasonal variations in the load on power transmission lines; See Time of day & Season Affect EMF Strength for details.
• EMF measurements of local EMF sources such as appliances are entirely sensitive to whether or not the appliance is turned on and in-use as well as to variations in electrical current depending on appliance settings.
• Because RF and EMF measurement tools need to be properly chosen to measure the particular type and frequency of RF or EMF signal that is of interest, be sure to also see EMF RF FIELD & FREQUENCY DEFINITIONS for a simple explanation of different types of radio frequency (RF) and electromagnetic frequency (EMF) types and where they are found.
• See Definitions of Gauss vs Milligauss for details about gauss and milligauss and definitions of these terms

Inconsistency in EMF measurement methods is a problem: In order to permit comparison of measurements (and studies) it is important not only to have line load data available (for researchers) but also that site measurements are made in a very consistent manner from building to building.

To do otherwise would make it impossible to compare conditions at one property with those at another, even if both properties are equidistant from the same power line and even if both measurements were made at the same moment.

Position-insensitive EMF Measurement Instruments - best for the amateur

Position-sensitive EMF Measuring Instruments - Why and How They are Used

EMF Polarity and Shape, not just Distance, Affect some EMF Measurements

Electromagnetic fields are created around power transmission lines by the passage of high levels of current through the transmission line wires themselves. A power-line generated electromagnetic field has polarity and shape, roughly spherical around a power line.

The problem of the electromagnetic field having polarity and shape means that some early or low-cost EMF measuring devices will give widely varying field strength measurements depending simply on the physical orientation of the device when the measurement is made - that is, what direction you point the instrument affects its reading.

But don't think that pointing directly towards the power line wires overhead gives the maximum reading.

It may not, due to field polarity. More costly EMF meters have multiple sensors to overcome this defect.

We discuss the problem of electromagnetic field shape, polarity, and instrument testing sensitivity to instrument orientation or position at Sensitivity & Accuracy of EMF Measuring Instruments.

Please do not contact us with a request buy EMF or RF measuring equipment. We do not sell anything. To do so would be a conflict of interest for this website. These devices are readily available from many electrical equipment and home inspection equipment suppliers. See Evaluation of Low-Cost EMF Instruments where we describe several low-cost and reasonably accurate EMF measurement devices that are readily available. See Radio Frequency RF Detection Meters where we describe several low-cost and accurate radio frequency or RF detection and measurement devices suitable for radio, TV, cellphone, microwave, and similar signals.

Instead of contacting us with a request to perform EMF Electromagnetic or RF Radio Frequency Field Strength measurements, in most cases it is more economical and convenient for a property owner to purchase their own instrument, making measurements under varying conditions. In this series of articles we describe how to make measurements using a consistent approach and using good documentation. See Recommended EMF Measurement Procedure for details of how to collect EMF measurement data.

Following good procedure and using instruments properly are two steps towards making accurate, repeatable EMF measurements. But because the signal transmission for RF sources such as radio, TV, or cell towers, the load on a power transmission line is not under control of an individual property owner, and because the EMF strength varies as the power transmission line load varies, it is important to have an idea of that condition as well when attempting to characterize EMF exposure at a specific location. In contrast, EMF measurements are quite accurate and repeatable at other EMF sources such as close to electrical appliances and service entry cables.

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Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

ENVIRO-SCARE, EMF & Property Values
ENVIRO-SCARE Defined, Effects
ENVIRO-SCARE Effects on Property Values
EMF Cancer Scare
EMF RF FIELD & FREQUENCY DEFINITIONS
EMF ELECTROMAGNETIC FIELDS & HUMAN EXPOSURE
EMF Levels of Cancer Risk
EMF MEASUREMENT INSTRUMENTS
EMF MEASUREMENT PROCEDURES
EMF SURVEY PROCEDURE - Details
  Introduction to EMF Measurement
  EMF/EMR Measurement Procedure Overview
    EMF Variability
    Electrical Utility Workers & EMF Exposure
    EMF Instrument Sensitivity & Accuracy
    EMF Polarity & Shape Affect Measurements
    Distance from the EMF Source Affects Strength
    Time of day & Season Affect EMF Strength
  Local EMF Sources May Exceed Power Line Strength
  Recommended EMF Measurement Procedure
    Outside EMF Measurements
    Outside EMF Measurement Documentation
    Indoor EMF Measurements
    Other Indoor EMF Measurement Targets
    Workplace EMF Measurements
  EMF Measurement Documentation Details
  EMF Measurement Instrument Use
    Definitions of Gauss vs Milligauss
    Position-sensitive EMF Instrument Readings
  Interpreting Electromagnetic Field Strength EMF Survey
  Evaluation of Low-Cost EMF Instruments
    Accuracy & Calibration of EMF Instruments
    Calibration of EMF Instruments in the Field
    Calibration of EMF Instruments by Electric Company
  Electromagnetic Field EMF ELF Detection Instruments
    F.W. Bell Model 4060 ELF Meter
    Safeco™ analog EMF ELF EMR meter
    Walker Scientific ELF-50D™ Digital EMF Meter
  Radio Frequency RF Detection Meters
    BK RF Measurement Test Equipment
    Mobile Design Shipboard RF Measurements
    Safe Living RF Meters - Radio Frequency Detectors
    Zap Checker Radio Frequency Detection Hand Held Instruments
References for Electromagnetic Fields and Cancer
WORKSHEET for EMF MEASUREMENTS
WORKSHEET for EMF MEASUREMENTS - Example
WORKPLACE EXPOSURE to Electromagnetic Fields

References for Electromagnetic Fields and Cancer Risk/Carcinogenicity

• Electric Power Lines, Electromagnetic Fields, Cancer Risk, & "Enviro-Scare" - The Normal Curve Cycle of Public Fear About Environmental Issues - online document by DF
• A Procedure for Measuring EMF electromagnetic fields online document by DF
• "Questions and Answers about Biological Effects and Potential Hazards of Radiofrequency Electromagnetic Fields", Federal Communications Commission, Office of Engineering and Technology, US FCC, OET Bulleting 56, 4th Edition, August 1999
  " Many consumer and industrial products and applications make use of some form of electromagnetic energy. One type of electromagnetic energy that is of increasing importance worldwide is radiofrequency (or "RF") energy, including radio waves and microwaves, which is used for providing telecommunications, broadcast and other services. In the United States the Federal Communications Commission (FCC) authorizes or licenses most RF telecommunications services, facilities, and devices used by the public, industry and state and local governmental organizations. Because of its regulatory responsibilities in this area the FCC often receives inquiries concerning whether there are potential safety hazards due to human exposure to RF energy emitted by FCC-regulated transmitters. Heightened awareness of the expanding use of RF technology has led some people to speculate that "electromagnetic pollution" is causing significant risks to human health from environmental RF electromagnetic fields. This document is designed to provide factual information and to answer some of the most commonly asked questions related to this topic." - original source: U.S. Federal Communications Commission Office of Engineering and Technology, http://www.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet56/oet56e4.pdf
• EMF RF FIELD & FREQUENCY DEFINITIONS RF and EMF measurement tools need to be properly chosen to measure the particular type and frequency of RF or EMF signal that is of interest. See EMF RF FIELD & FREQUENCY DEFINITIONS for a simple explanation of different types of radio frequency (RF) and electromagnetic frequency (EMF) types and where they are found.
• Definitions of Gauss vs Milligauss for details about gauss and milligauss and definitions of these terms.
• Consumer Product Safety Commission, 800-638-CPSC.
• US Environmental Protection Agency, Office of Pesticides and Toxic Substances, TSCA Assistance Office (TS-799), 800-424-9065 or 202-554-1404.
• "Evaluation of Potential Carcinogenicity of Electromagnetic Fields," EPA Report #EPA/600/6-90/005B October 1990. EPA: 513/569-7562.
• "Biological Effects of Power Frequency Electric and Magnetic Fields" background paper, prepared as part of OTA's assessment of "Electric Power Wheeling and Dealing: Technological Considerations for Increasing Competition," prepared for OTA by Indira Nair, M. Granger Morgan, H. Keith Florig, Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA 15213
• "Biological Effects of Power Line Fields," New York State Powerline Project. Scientific Advisory Board Final Report, July 1, 1987.
• "Extremely Low Frequency (ELF) Fields," Environmental Health Criteria 35. World Health Organization, Geneva, 1984.
• "Electric and Magnetic Fields at Extremely Low Frequencies: Interactions with Biological Systems. In: Non ionizing Radiation Protection, World Health Organization, Regional Office for Europe, Copenhagen, 1987.
• "Electric and Magnetic Fields from 60 Hertz Electric Power: What do we know about possible health risks?," Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA 15213 1989.
• "Electromagnetic Fields Are Being Scrutinized for Linkage to Cancer," Sandra Blakeslee, New York Times, Medical Science section, April 2, 1991

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
• Electric Power Lines, Electromagnetic Fields, Cancer Risk, & "Enviro-Scare" - The Normal Curve Cycle of Public Fear of Environmental Issues
• Electromagnetic Fields in the Workplace sample very good NIOSH document online, links to other NIOSH docs.
• Electromagnetic Field Surveys & Hazards full list of our links to services and technical article
• Electric Power Lines, Electromagnetic Fields, Cancer Risk, & "Enviro-Scare" - The Normal Curve Cycle of Public Fear About Environmental Issues - online document by DF
• A Procedure for Measuring EMF electromagnetic fields online document by DF
• Environmental Concerns in Buildings, hazards: allergens, asbestos, brownfields
• ...

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