How NOT to measure Gauss values for PEMF devices
There are many inexpensive EMF meters for Gauss measurements on the market creating confusion about to perform correct Gauss measurements for intensities generated by PEMF devices. These Gauss meters start at $30 and expectations should match the price tag.
First of all these Gauss meters are designed to measure electromagnetic fields created by cell phones, radio waves, micro waves, power lines, antenna radiation, Wi-Fi detection etc. etc.
Then there are $1,000 tri-axis Gauss meters to be used for measuring DC/AC magnetic field strength of permanent magnet materials, motors, speakers, magnetic sensors, magnetic transducers and other machines and instruments.
Tri-axis Gauss meter
Popular Gauss meters are also used by people who are interested in paranormal activities and use them for ghost hunting.
They believe that ghosts emit and/or disturb electromagnetic fields and that Gauss meters can be used to detect ghost’s movements, thus calling them ghost meters.
Found a ghost?
Having said this however this does not necessarily mean that even expensive Gauss meters can be used for measuring PEMF intensities because “catching” and then measuring very fast PEMF pulses is not easy!
Placing such a meter in a strong, low frequency, pulsing electromagnetic field like a high intensity PEMF device, it reacts abnormally because the electronics inside are disturbed and overloaded, making correct Gauss measurements simply impossible.
Gauss meters measure the rate of changes in electromagnetic fields. The reading on these meters depends on the frequency range of the electromagnetic changes.
There are two different kinds of Gauss meters: “frequency-weighted” or “non-frequency-weighted”.
Gauss meters consist of an inductor coil connected to an amplifier, while an AC oscillating magnetic field will create a very small current inside the inductor coil. This signal is then amplified, filtered and rectified in a DC voltage. The measured signal frequency is then proportional to the displayed magnetic field strength.
Please note that the sensitivity of the meter depends on the frequency of the electromagnetic field!
Frequency-weighted Gauss meters
Inexpensive Gauss meters are usually frequency-weighted because non-frequency weighted technology is only used in more expensive meters. These Gauss meters measure frequencies over a very wide range and they will not give a true electromagnetic value because the higher the frequency to be measured, the higher the value “measured”. These values cannot be relied upon as being accurate and sometimes measure a Gauss value hundreds of times higher than it actually is. This is the reason why these frequency weighted meters are factory calibrated for Gauss values at 50 or 60 Hz.
Sensitivity of such Gauss meters may sometimes be proportional in a specific frequency range, then become linear in the next frequency range and then even be reversed in the following frequency range!
Non-frequency-weighted Gauss meters
Non-frequency weighted Gauss meters give a fairly flat frequency response, regardless of the frequency.
These instruments are accurate for laboratory work, because they show more or less the real field strength instead of a frequency dependent strength.
So how about Gauss meters for measurement of fast PEMF pulses? Well we purchased such a peak Gauss measurement device specially designed for this purpose and started testing it.
In communications with the manufacturer of the device we received the following information. The measurement coil has a 1” diameter single-turn detector loop while at the same time writing that this is a Helmholtz coil. Because a Helmholtz coil always consists of two exact identical coils placed symmetrically along the same axis, a single loop can never be a Helmholtz coil so we decided to look further.
When asking about the calibration procedure the manufacturer wrote: A 1000 Gauss reference magnet is used in which the coil is pulled out to record the peak.
Then we looked into the way the peak measurements are recorded. As we already expected, an electronic (sample-and-hold circuit) is used. The manufacturer claimed that the device is able to measure individual pulses as short as 1 microsecond.
In electronics a sample and hold circuit is used to “grab” a signal and then “hold” the signal for displaying the measured information. Inexpensive devices make use of such electronic sample and hold circuits.
Such a circuit is created by charging a capacitor with the sampled signal and then holding this charge for a while to allow for a read out. Because the charging time of a capacitor is non-linear, only the linear part of this charging curve can be used, otherwise a complicated anti-logarithmic amplifier must be used to correct measurement failures. Alternatively, the capacitor charge is compared to values in a preset table with similar inaccuracies.
This limits the measurement abilities drastically and the higher the peak value of the PEMF pulse the larger the measurements mistakes.
Let’s now look at another problem measuring maximum PEMF peak values. During the measurement, a time window is opened to catch the PEMF pulse. What happens with such meters is that during the measurement time (possibly around one second) a “time window” is opened to let the PEMF peak value “through” to the sample catching mode and thus creates another source for critical Gauss measurement mistakes.
Let’s now look at the actual pulse form of a PEMF device inside the applicator coil. A so called “ringer” signal consists of a series of pulses slowly fading out during each individual pulse.
Because of the time the measurement window is open, not only can the first maximum peak pulse can be “grabbed” (blue area), but in addition more of these fading pulses (black area) are usually “grabbed”, unless this procedure is stopped by closing the window.
These additional smaller pulses are then accumulated to the previous peak value when more than one of the “ringer” pulses pass through this time window. The following smaller pulses are now added to the previous value completely distorting the peak Gauss value results by showing a much higher Gauss value on the meter than generated in reality.
Because we are only interested in the maximum PEMF peak value of a single pulse and not the accumulated energy inside the fading pulse, we can never be sure that the real maximum peak value of such a PEMF pulse is measured, if the above measurement method is used!
Conclusion: Can an inexpensive Gauss measurement device be used for defining the maximum intensity of a PEMF device? The answer is absolutely not!
Now the next question is how the maximum intensity of a PEMF device should be measured, because some manufacturers make wild and unsubstantiated Gauss value claims, far exceeding reality.
To know how to correctly measure Gauss values go to the