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Development of Near-Field Electric Energy Density Meter Model EDM-2

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Donald R. Belsher · 1975

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NIOSH's 1975 development of specialized EMF measurement equipment shows decades-old recognition of electromagnetic exposure risks.

Plain English Summary

Summary written for general audiences

NIOSH developed the EDM-2, a specialized instrument designed to measure electric energy density in near-field electromagnetic environments. This technical report documented the engineering and calibration of equipment used to quantify EMF exposures in workplace and environmental settings. The meter represents early efforts to create standardized tools for measuring electromagnetic field strength close to EMF sources.

Why This Matters

This 1975 NIOSH technical report represents a crucial milestone in EMF measurement technology development. The creation of the EDM-2 electric energy density meter reflects growing recognition among occupational health agencies that accurate EMF measurement tools were essential for protecting workers and the public. Near-field measurements are particularly important because they capture the highest exposures that occur close to EMF sources, before the fields disperse with distance.

What makes this significant is the timing. NIOSH was developing sophisticated measurement equipment nearly five decades ago, demonstrating that concerns about electromagnetic exposures were serious enough to warrant federal investment in specialized instrumentation. Today's ubiquitous wireless devices create near-field exposures similar to those this meter was designed to measure, yet most people remain unaware of these exposure levels in their daily environment.

Exposure Details

Power Density
1800 mW/cm²

Exposure Context

This study used 1800 mW/cm² for radio frequency:

Building Biology guidelines are practitioner-based limits from real-world assessments. BioInitiative Report recommendations are based on peer-reviewed science. Check Your Exposure to compare your own measurements.

Where This Falls on the Concern Scale

Study Exposure Level in ContextStudy Exposure Level in ContextThis study: 1800 mW/cm²Extreme Concern - 1,000 µW/m²FCC Limit - 10M µW/m²Effects observed in the Extreme Concern range (Building Biology)This level is 1,800 times the FCC limit
A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 10 MHz to 500 MHz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 10 MHz to 500 MHzPower lines50/60 HzCell phones~1 GHzWiFi2.4 GHz5G mm28 GHzLogarithmic scale

Study Details

To develop an electric-field survey monitor (EDM-2) for measuring occupational exposure to radiofrequency (RF) radiation from 10 to 300 MHz, specifically for use in assessing exposure from industrial RF power sources.

The monitor employs a set of three orthogonal dipoles to obtain an essentially isotropic response. T...

The EDM-2 meter has usable full scale ranges in a planewave field of 30, 10, 3, 1, 0.3, 0.1, 0.03, 0...

The EDM-2 meter provides substantial improvement over previous meters of this type. These improvements include a faster rise and fall time for pulse response, a dynamic range of 50 dB, lower noise preamplifiers, a greatly reduced temperature sensitivity, a flat response (to within + 1.0 dB) from 10 MHz through 500 MHz as well as other refinements. Electric energy density provides a reasonable index of a large class of microwave radiation hazards and is simpler to measure in a near field than is energy flow.

Cite This Study
Donald R. Belsher (1975). Development of Near-Field Electric Energy Density Meter Model EDM-2.
Show BibTeX
@article{development_of_near_field_electric_energy_density_meter_model_edm_2_g18,
  author = {Donald R. Belsher},
  title = {Development of Near-Field Electric Energy Density Meter Model EDM-2},
  year = {1975},
  
  
}
No DOI on file for this study.

Quick Questions About This Study

EDM-2 stands for Electric Energy Density Meter model 2, a specialized instrument developed by NIOSH to measure electromagnetic field strength in near-field environments where exposures are typically highest.
NIOSH developed the EDM-2 to provide accurate measurements of electromagnetic field exposures in workplace settings, reflecting growing concerns about potential health effects from EMF sources in occupational environments.
Near-field measurement captures electromagnetic field strength close to EMF sources, where exposures are highest before fields weaken with distance. This provides the most accurate assessment of actual human exposure levels.
The EDM-2's development shows that federal agencies recognized EMF exposure risks decades ago, using specialized equipment to measure fields similar to those created by today's wireless devices and electronics.
The EDM-2 represented advanced measurement technology for its time, providing standardized methods to quantify electromagnetic exposures that were previously difficult to measure accurately in workplace and environmental settings.