Electric fields measured with a spectrum analyzer

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I am looking at 60Hz household power with a low frequency spectrum analyzer and finding the electric field varies from a peak at 60Hz where I would expect it. Rather I find the field peak may vary plus or minus 5Hz.

AND that the area under the trace may be scewed (?) to the left or right of 60Hz rather than present as a normal distribution curve. Does this suggest anything?

I have photos of the screens that are available.

Thanks
 

ELA

Senior Member
Occupation
Electrical Test Engineer
I have used Spectrum Analyzers for looking at high Frequency electric fields but never for 60 hz "electric fields". What type of antenna are you using? It would have to be awfully long to capture an electric field at 60hz.
 
E-fields

E-fields

I am doing safety inspections. The antenna is built in to the analyzer which is made to measure EMF and e-fields.
Thanks
 
There are two types of fields, electromagnetic and electric fields. The danger factor for electromagnetic fields fields is not well established, however, electric fields are established to be dangerous.

The device being used is a quality instrument from Germany, yes I also have gaussmeters, they are also not toys. This spectrum analyzer is able to examine frequencies from 0 to one MHz, show the frequency, signal strength, waterfall, log, etc. It is not a toy. For further information on the instrument, google Aaronia spectran.

The International Institute for Bau-Biolgie (building biology) has a standard for e-fields in sleeping areas of a maximum of 6 V/M.

Back to my question. I am finding shifts in the e-field from 60Hz, i.e. the maximum field strength is NOT at 60Hz but has been found to vary by several Hz thru time. Does anyone have suggestions as to causality?
Is such variance found in mains wiring or can electrical devices on the circuit produce changes in the e-field of the entire home, or?
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
080811-1630 EST

fields5491:

Power line frequency fluctuates around a mean of 60 Hz. Averaged over a 24 hour period it will be almost exactly 60 Hz. The cumulative error over a year is probably next to 0%. This averaging is done to keep electric clocks correct. There is probably less than 1 second error per year which would be 60 parts in 3600*24*365 or 1 part in 525,600 = 0.000,19 %.

Charlie of post #6 can probably give you some better information on frequency variation during the day and maximum cumulative error per year.


ELA:

You should be able to put two insulated plates or wires 1 meter apart and a high impedance voltmeter between then to measure electric field intensity. Obviously you could use some other spacing.

http://www.smeter.net/daily-facts/4/fact25.php
Breakdown voltage of about 3,000,000 per meter at sea level. About 76,000 V/in, and 7600 V/0.1 inch.

A typical person is a little less than 2 meters tall. At 12 V head to toe this might produce a noticeable current in a person. At 100,000 ohms this is 0.000,12 amps (0.12 MA). Based on the article below this analysis might not be very valid.

This is an older article but very interesting from a general view. Animals navigating by use of the earth's magnetic field. I have not read the whole paper yet.
http://www.calpoly.edu/~dhafemei/background2.html

Apparently there are some low cost meters that have both electric field and magnetic field modes.

.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
080820-0757 EST

More on line frequency.

As I mentioned in another thread with my Fluke 87 I was typically reading 60.00 and 59.99 Hz.

I have now made some readings with my BK Precision 1822 Frequency Meter using the period mode averaged over 100 cycles, 100/60 seconds. The results were in microseconds and calculated frequency in Hz from the period measurement:

Period measurement is used to obtain greater accuracy in a short time on a low frequency. The worst deviation in this short time frame was 0.0114 HZ or 0.02%.

----- MS -------- Hz --

--- 16664.3 --- 60.0085
--- 16664.2 --- 60.0089
--- 16663.9 --- 60.0100
--- 16663.5 --- 60.0114
--- 16664.3 --- 60.0085
--- 16664.7 --- 60.0071
--- 16664.7 --- 60.0071
--- 16665.2 --- 60.0053
--- 16665.3 --- 60.0049
--- 16665.4 --- 60.0046
--- 16666.0 --- 60.0024
--- 16666.1 --- 60.0020
--- 16666.6 --- 60.0002
--- 16666.7 --- 59.9999
--- 16667.3 --- 59.9977
--- 16667.1 --- 59.9984
--- 16666.7 --- 59.9999
--- 16666.8 --- 59.9995
--- 16667.3 --- 59.9977
--- 16667.7 --- 59.9963
--- 16667.7 --- 59.9963
--- 16667.8 --- 59.9995
--- 16667.6 --- 59.9966
--- 16667.2 --- 59.9981
--- 16667.1 --- 59.9984.
--- 16667.5 --- 59.9970
--- 16668.1 --- 59.9970
--- 16668.2 --- 59.9945.
--- 16668.6 --- 59.9930.
--- 16668.4 --- 59.9938
--- 16668.2 --- 59.9945
--- 16668.3 --- 59.9941
--- 16667.9 --- 59.9956
--- 16667.6 --- 59.9966
--- 16667.1 --- 59.9984
--- 16667.2 --- 59.9981

Over this short time frequency stability is very good.

.
 
Your frequency is very stable, more so than where I live. However, I am measuring electric field and find that the frequency of the peak electric field varies and tends toward the high side above 60Hz. Here is some logged data of the electric field
Freq (khz) Value
0.060 3.767889499664 V/m
0.060 3.572333097458 V/m
0.060 3.654189825058 V/m
0.060 3.523371934891 V/m
0.060 3.625167608261 V/m
0.060 3.646473646164 V/m
0.060 3.655314445496 V/m
0.060 3.728591680527 V/m
0.061 3.718662738800 V/m
0.061 3.718189239502 V/m
0.060 3.763057947159 V/m
0.060 3.807860612869 V/m
0.060 3.719767332077 V/m
0.061 3.785293579102 V/m
0.060 3.798756837845 V/m
0.061 3.759781599045 V/m
0.060 3.787307977676 V/m
0.060 3.724339485168 V/m
0.061 3.719924926758 V/m
0.061 3.569867849350 V/m
0.061 3.693008661270 V/m
0.060 3.817403793335 V/m
0.060 3.397884368896 V/m
0.060 3.444200277328 V/m
0.059 3.287812709808 V/m
0.060 3.313416004181 V/m
0.061 3.580045700073 V/m
0.060 3.424035549164 V/m

The frequency is not logged to exact decimals as you see, however I often find 61.4Hz. (The readings taken at one second intervals.) The field is being measured in the air, not connected to any AC line.
I am wondering why the net electric field does not average 60Hz. Is this an abnormality? Subtle, but I wonder if there are consequences.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
080820-1058 EST

fields5491:

It is important to determine how the instrumewnt is measuring frequency.

I am guessing my Fluke 87 measures frequency by the period method and then displays the reciprocal, or frequency. The reason for my deduction is that measurement time seems short, about 1 second, and the accuracy is much better than would be obtained with a random 1 second gate.

When I tried a line frequency measurement in the frequency mode on my BK instrument the results were very poor even with a 10 second gate. The best possible with this method would provide an accuracy arround 1 part in 600 unless special means were used to synchronize the gate time with a first zero crossing and interpolate to the last zero crossing.

To know how an instrument makes its measurements is critical to knowing the validity of the measurements. A calculator can give you a very precise incorrect answer if you put the wrong data or operations into it.

.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
fields5491 said:
The frequency is not logged to exact decimals as you see, however I often find 61.4Hz. (The readings taken at one second intervals.)
I don't know where that frequency is coming from, but it is not directly from the grid. The grid protection systems would have shut it down long before you got to 61.4 Hz on the grid itself.
 

ELA

Senior Member
Occupation
Electrical Test Engineer
fields5491 said:
Here is some logged data of the electric field
Freq (khz) Value
0.060 3.767889499664 V/m

The frequency is not logged to exact decimals as you see, however I often find 61.4Hz. (The readings taken at one second intervals.) The field is being measured in the air, not connected to any AC line.
I am wondering why the net electric field does not average 60Hz. Is this an abnormality? Subtle, but I wonder if there are consequences.

Your initial use of the term Spectrum Analyzer (and theirs) threw me off. I would refer to this as a field strength meter.
In an earlier post you mentioned this was not a toy and to google for information on the device.
I did. What model ? I could not find an accuracy statistic. Since your data log was in Khz my guess it is not very accurate at 60Hz.
 
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