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This article explains how to use EMF or ELF measuring instruments when performing electromagnetic field (EMF) or electro-magnetic radiation EMR measurements either by engaging a professional or by consumers using low-cost instruments which 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.

© Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this 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.

EMF Measurement Instrument Use

For position-insensitive equipment, a single reading is usually provided, directly in mG.

For position sensitive equipment you'll find an enormous range of response depending on the angle and direction in which you hold the measurement device.

While this type of instrument is more work to use (see calculations below and in spread sheet) it provides more clear indication of when you're approaching a field. Some instruments do not provide a reading directly in mG and you'll have to simply record the "raw" measurements and to convert them later.

Definition of Gauss versus Milligauss Field Strength Measurements

Some readers may be confused between two common terms used to describe the strength of an electromagnetic field: Gauss and Milligauss. Both of these terms measure the same effect, but at different ranges of strength level. It's simply a matter of moving the decimal point, as we demonstrate in our photographs above.

In our first photo (above left) the ELF EMF meter has been set to the Gauss range and we are measuring a field strength of 0.03 Gauss with our meter touching a small power transformer.

In our second photo (above right) the same ELF EMF meter has been set to its more-sensitive Milligauss range and we are measuring 25 milligauss.

Because usually the electromagnetic field strength around residential properties is very weak, most measurements will probably be made in the milligauss range. 0.03 Gauss is the same as 30 Milligauss. Our instrument, more accurate in the lower milligauss range, shows that we are actually measuring 25 milligauss, a number which was rounded up to 0.03 Gauss when the scale was shifted.

Definitions of Gauss and Milligauss for Measuring Electromagnetic Fields - EMF

Gauss is a measurement scale used to measure the strength of an electromagnetic field (EMF). The gauss level measured in a given location depends on the strength of the source of the EMF and the distance from the source. The measured field strength of an EMF falls off quite rapidly with distance (field strength declines as the square of the distance from the source).

When electrical current flows through a wire (such as in an electrical distribution wire or inside of an electric motor) an electromagnetic field is produced. Power lines, local electrical wires, air conditioning motors, computers, TVs, hair dryers, toasters, all devices that use or transport electricity will produce an electromagnetic field. Usually the strength of these fields is low (Electric fan 1 mG, TV 1mG, chain saw 2.5 mg(?) at chest height, electric stove 6 mG, older electric blankets before circuit redesign 20 mG, and under a distribution line for electrical power transmission, 2-20 mg depending on the line height, KVA rating, and actual level of usage at the time of measurement.

If there is a concern for measuring exposure or possible exposure to electromagnetic fields, it's critical that we have a correct understanding of the levels of exposure that are being examined. For example, one of our readers informs us that that manufacturer of his pacemaker recommends avoiding exposure to electromagnetic fields stronger than 5 gauss. (EMF generated from small electric motors (such as a chain saw) measured with the saw held in normal operating position may be as much as 2.6 Gauss at the user's chest.)

When recording EMF measurements be certain that you've got the right order of magnitude.

1 Milligauss (mG) = 10^-3 Gauss, or 0.001 Gauss

Published sources provide lots of examples of producing and measuring electromagnetic fields at a known gauss level. For example, using a 1.5V battery and a 150 Ohm resistor to make a long straight wire circuit, the EMF field strength when measured at 0.1m (about 4") from the wire will be about 0.2 milligauss (mG).

NIST, focused on SI units, measures electromagnetic fields in Tesla units of magnetic flux density: magnetic flux density Tesla, Symbol: T
SI Derived unit: Wb/m2
SI Base: kg·s-2·A-1
and
Magnetic Fluxe is measured in
Weber, Symbol: Wb
SI Derived Unit: V·s
SI Base Units: m2·kg·s-2·A-1

For Position-sensitive EMF measurement instruments, three readings are necessary.

1. Horizontal (spin through 360 degrees and record highest reading)

2. Vertical (same as above)

3. Pointed towards suspected source (e.g. distant power line

To compute the actual point measurement, each of these numbers, once converted to mG, must be squared, the three squares added, and the square root taken of the sum. This is because the measurement scale is not linear, so a direct raw average would be incorrect.

In the EXCEL worksheet which we provide (at WORKSHEET for EMF MEASUREMENTS) you will observe that provision is made for recording raw data points as well as the individual mG readings. Formulas embedded in the worksheet compute the mean square average in order to obtain a valid point measurement of emf strength by this method.

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 This article describes several low-cost and reasonably accurate EMF measurement devices that are readily available. See Radio Frequency RF Detection Meters This article describes 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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  EMF Measurement Instrument Use
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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
• "Magnetic Field Exposure and Cancer: Questions and Answers [ copy on file as /emf/EMF_Fact_Sheet_NCI_NIH.pdf ] - ," National Cancer Institute, U.S. National Institutes of Health, web search September 2010, original source: http://www.cancer.gov/cancertopics/factsheet/Risk/magnetic-fields
  makes these five key points about EMF
  • Electric and magnetic fields (EMF) are areas of energy that surround any electrical device. EMFs are produced by power lines, electrical wiring, and appliances (see Question 1).
  • Electric fields are easily shielded or weakened by walls and other objects, whereas magnetic fields are not. Since magnetic fields are more likely to penetrate the body, they are the component of EMFs that are usually studied in relation to cancer (see Question 1).
  • Overall, there is limited evidence that magnetic fields cause childhood leukemia, and there is inadequate evidence that these magnetic fields cause other cancers in children (see Question 2).
  • Studies of magnetic field exposure from power lines and electric blankets in adults show little evidence of an association with leukemia, brain tumors, or breast cancer (see Question 3).
  • Past studies of occupational magnetic field exposure in adults showed very small increases in leukemia and brain tumors. However, more recent, well-conducted studies have shown inconsistent associations with leukemia, brain tumors, and breast cancer (see Question 4).
• 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 & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
• 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
• 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.

• Environmental Concerns in buildings, hazards: allergens, asbestos, brownfields, - above ground or buried oil storage tanks, - A Procedure for Measuring EMF electromagnetic fields, - Electric Power Lines, Electromagnetic Fields, Cancer Risk, & "Enviro-Scare" - The Normal Curve Cycle of Public Fear of Environmental Issues - toxic gases & odors, IAQ, lead paint, - toxic mold inspections, - mold test kits - how to send a mold sample to our lab using an inexpensive and superior method - radon, sick buildings, UFFI (urea formaldehyde foam insulation), - sewage septic backup contamination testing & cleanup - water testing for bacteria, lead, etc.
• Electromagnetic Field Surveys & Hazards full list of our links to services and technical articles

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