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Post Time: 12/08/2008 19:54:52 |
fshui9
Total Forum Posts: 10 |
Hi Alasdair.
Thanks for your feedback on my last posts.
You may recall our exchanges of a few months ago about the Field meters. Comparing the readings of electrical fields with the Gigahertz solutions 3030B and the Powerwatch Pro meter, I am getting approximately double with the 3030B on all readings. As advised this is without the earthing lead and holding both with the two fingers and thumb as advised.
Examples: Pro: 6 v/m - 3030B: 11v/m pro: 40 v/m 3030B 77 v/m
I am wondering why there is s such a huge discrepancy. can you shed any light?
regards
Robert Gray |
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Post Time: 14/08/2008 04:25:06 |
topazg
Total Forum Posts: 13 |
Hi Robert
That is more that I would expect. We have some of both here and will re-investigate those. It may be necessary to borrow yours for a few days depending on the results we get with ours. We will also compare the readings with our two Holoday 3604 ELF meters.
When we first started selling the 3030B's, we felt they were slightly over-reading, both in the field and between our calibration plates. Gighertz strongly disagreed with our claims. They have good test rigs. Electric fields are notoriously difficult to measure and are affected by the person holding the meter and nearby objects. The Pro was designed and extensively tested to give a good indication of what a person standing at a location would be experiencing - i.e. the person forms part of the measuring device calibration. We still think that is the most appropriate way to measure E-fields re.peoples' exposures. The electrical industry insists of "unpeturbed" readings with no-one within about 3 metres of the mesurement instrument. The trouble is, the presence of a person can increase the electric field (say within 20 metres of high-voltage over-head wires) by 1000 to 10000-fold! Surely, you want the measurement with the person present? (They don't, of course!).
The 3030B is calibrated to use the Earthing lead. But that gives an absolute reading between where you are measure and some good, but remote, Earth. It does not indicate what a person standing there is exposed to. In our initial trials we found that it was still higher tha the Pro, but only by a small amound (maybe 10 to 20%) when used without the Earthing lead. That is what we recommend for general EMF-Health use.
We will do some more tests and return the results to here.
Topazg (Grahamp), Powerwatch Technical Manager
Andrew Cohen, Powerwatch Senior Engineering Technician
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Post Time: 15/08/2008 20:28:43 |
fshui9
Total Forum Posts: 10 |
Hi Alasdair
Thanks for that. I look forward to getting the test results.
Two of us did more comparitive readings today and pretty much got the same in most of them ie between 80 and 100% more than the pro readings (electrical readings only). Strangely there were 1 or 2 readings where the differential was substantially less (around the 20% mark as you suggested)- but the vast majority were as indicated earlier.
We were careful to ensure that we were comparing like with like by having the body and meter in exactly the same place. We have only conducted these trials with 1 'pro' and 1 '3030B', so I suppose its possible that 1 of them has a calibration away from the norm for it's type, though, from what you have said before, this is perhaps unlikely. Tomorrow, we will have several meters to trial and so I will check to see if I can discern any differences between them. |
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Post Time: 26/08/2008 21:30:52 |
fshui9
Total Forum Posts: 10 |
Hi Topazg, Andrew
I refer to your post of 14th August.
I am sure you are very busy but I wonder if you would be able to give me some idea of when you might be able to post results of your comparative checks on the 3030B?
Thanks
Robert |
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Post Time: 27/02/2009 17:57:04 |
fshui9
Total Forum Posts: 10 |
Hi Topazg, Andrew, Alasdair
I refer to your post of 14th August. and my unanswered responses on15th August and again on the 24th August.
I am sure you are very busy but I wonder if you would be able to give me some idea of when you might be able to post results of your comparative checks on the 3030B?
Thanks
Robert |
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Post Time: 02/03/2009 17:31:50 |
alasdairP
Total Forum Posts: 173 |
Hi, Robert, I apologise that we not responded further on this issue. I thought we had.
The EMFields Pro and the Gigahertz 3030B can appear to give quite different electric field readings, with the 3030B often presenting a figure roughly twice that of the EMFields Pro. This is not a calibration error or inaccuracy, but is instead due to a different method of assessing the electric field.
The 3030B is designed to measure the electric field at the end of the instrument in direct relation to ground. This is why they recommend using the earthing lead they provide with the instrument, and using this lead is required for your measurement of the electric field relative to ground to be accurate with respect to the ground. This will always give a considerably higher measurement reading, unless you are standing with bare feet on an earthed conductive surface.
The Pro is designed to measure the electric field level to which your body is experiencing, so it is relative to your body, instead of to ground. This was intentional as we believe that it is the actual fields that your body is experiencing that matters most.
An example of the difference is illustrated here. Birds can perch on very high-voltage powerlines without being injured. This is because they only have a low number of volts actually across their body. However, they are technically sitting at hundreds of thousands of volts relative to the Earth. In this situation, the 3030B would read hundreds of thousands of volts (way over scale and it would be permanently damaged), but the Pro would read only a few hundred or less.
The 3030B can be used like the Pro (without the earthing lead), but if used this way it still gives higher readings. If held in the same manner as the Pro (at the bottom, around the battery compartment) then it reads roughly twice as high as the EMFields Pro.
The Bau-biology people also recommend using an actual electric voltmeter to measure the millivolts between a person and a good ground/earthing point. This gives another metric with which to assess electric field exposure.
The best thing is to use the same meter and get a feel for different locations. The numbers we give for advice are based on EMFields Pro readings.
As usual with EMF matters, there is no black or white answer. Whatever meter you use, the lower the reading, the better. If you use a 3030B meter, then the readings will typically be about twice as high as an Pro reading for the resons explained above. Neither are right or wrong in absolute terms.
Alasdair |
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Post Time: 02/03/2009 20:33:14 |
fshui9
Total Forum Posts: 10 |
Thanks Alasdair
That is exactly what I found - doubled up readings- and so makes good sense.
Thanks for the explanation.
Robert |
