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The EMFields AM11 Acoustimeter is a powerful radiofrequency (RF)/microwave detector. It measures both peak and average signals using a combination of LEDs and number readings on an bright text screen. The AM11 detects almost all modern wireless technology, including mobile phones, cordless phones, smart meters and WiFi, Bluetooth and RFID. The instrument is suitable for those with severe electrosensitivity as it is sensitive down to 0.02 V/m. It also has an audio output that helps determine the source of the exposure.


The Acoustimeter will help you quickly understand your RF environment. It accurately measures all incoming radiation from 200 MHz to 8000 MHz (8 GHz) which includes 3G, 4G and 5G, and was designed using many years of real life measurement experience.


The readings are shown on both an clear "OLED" text display and two sets of LED lights. The LEDs update rapidly, helping you to find hot-spots. The text display offers high accuracy with a lower update speed, giving you time to take note of the readings. You can easily determine what kind of device is causing your exposure using the internal speaker. Sound samples are available to help you identify what kind of signal your Acoustimeter is measuring. The sounds made by different devices change with time, so these are a rough guide only. If there are a number of sources of exposure, the sounds may mix and be harder to recognise.


If you can hear a very quiet "hissing" noise when no LEDs are lit, this is normal. This is from the internal workings of the Acoustimeter, and is therefore of no concern.


The Acoustimeter reads differently from some meters as:

  • It has a very fast response (up to over 8 GHz and reacts to very short pulses)
  • Peak readings are what they say – the highest sampled reading – and will react correctly to very short pulses that are regularly transmitted (such as from WiFi). The peak-hold reading on the OLED screen can be higher for some types of signal than the highest LED seen flashing as the Peak LED display does not show all the pulses in order to make it easier to see. The OLED peak-hold is the highest measured since "last cleared". It is cleared by switching the meter off and on again, or by pressing the "CLEAR (PEAK)" button
  • The Average reading is a true mathematical time-averaged rolling average of thousands of samples, updated 3 times each second. This gives the correct reading for DECT and WiFi and is much lower (DECT average power is about 0.01 of the DECT pulse power) than many other instruments which use the highest peak reading and then translate that into an equivalent average power. That is not correct as power is measured as total energy used/delivered per second and not the energy in a short pulse of say 10 milliseconds followed by a 990 ms gap. It is important that we understand this as most international standards are based on true average power (actually usually averaged over 6 minutes!).

N.B. The internal antenna is at the top rear of the case. Signals are best measured when the source is behind the instrument, but also quite good with the source to one or other side (particularly the left side away from the switches and volume control). It under-reads if the source is in front of the meter as the OLED display acts as an RF screen.

EMFields AM11 Acoustimeter

    • Two line LCD displaying actual levels:
        » Peak exposure levels in V/m
        » Peak hold levels in V/m
        » Average exposure levels in µW/m2
    • Two lines of LEDS displaying actual levels:
        » Peak exposure levels in V/m
        » Average exposure levels in µW/m2
    • Measurement range: 200 - 8 000 MHz ±6 dB ±0.02 V/m
    • Sensitivity (Peak Display): 0.02 V/m - 10.00 V/m
    • Sensitivity (Average Display): 0.1 µW/m2 - 250 000 µW/m2
    • LEDs go from 0.02 V/m - 6.00 V/m (peak) and 1 µW/m2 - 100 000 µW/m2
    • Internal loudspeaker with volume control
    • 3.5mm audio socket, which disables loudspeaker when in use
    • Audio can be heard below 0.02 V/m
    • Power source: 2x AA Alkaline or Rechargeable (1.2 - 1.5V)
    • Power draw: 100-150 mA at 3 V
    • Battery life: 20 hours
        » Typically 15 hours on two new 1500 mAhr AA alkaline cells and
        » Typically 25 hours on two charged 2700 mAhr NIMH rechargeable cells
    • Size (mm): 190 x 102 x 33 (LxWxD)
    • Weight: 280g, 330g with batteries

    Download Acoustimeter AM11 Manual

    Instrument updates from the manual

    Improvements over the AM10

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