Terence McCann Posted May 13, 2010 Author Report Share Posted May 13, 2010 I think, maybe, she was just scared . . . and rational or not, I didn't hold it against her. Well put. It is possible to guide without steering or taking sides. Quote Link to comment Share on other sites More sharing options...
CaoimhÃn P. Connell Posted June 13, 2010 Report Share Posted June 13, 2010 Hi Gents! I just thought I would poke my nose in and say hello! Actually, I do EMF testing, and to call residential EMF testing ââ¬Åvoodooâ⬠Quote Link to comment Share on other sites More sharing options...
Marc Posted June 13, 2010 Report Share Posted June 13, 2010 For a start, it is physically impossible to accurately and precisely measure EMFs from power lines - in fact, you can't even get a close estimate since its all near field stuff. Just moving a school bus two blocks away can change the readings. Itââ¬â¢s all near field stuff and so it canââ¬â¢t be done (regardless of what parameter one uses). The fact that EMF fields are influenced by conductive surfaces shouldn't mean that they cannot be measured. It just means that there are many other variables that influence the strength of EMFs. When clients voice their health concerns to me about EMF from nearby power lines and from cell phones, I suggest to them that the greater danger is too much sunshine and too many medical x-rays. They are both electromagnetic fields and the effects of those two on our health is well known. Marc Quote Link to comment Share on other sites More sharing options...
hausdok Posted June 13, 2010 Report Share Posted June 13, 2010 Hi CaoimhÃn, That was a very interesting and informative album. Thanks for sharing. ONE TEAM - ONE FIGHT!!! Mike Quote Link to comment Share on other sites More sharing options...
Terence McCann Posted June 13, 2010 Author Report Share Posted June 13, 2010 Whenever I perform residential EMF tests, the client MUST sign a waiver acknowledging that I told them the test results are COMPLETELY uninterpretable, and meaningless, and cannot be used for any reason, and the testing is a complete waste of their money. Cheers! CaoimhÃn P. Connell Forensic Industrial Hygienist www.forensic-applications.com CaoimhÃn, I have to ask... If you feel that: test results are COMPLETELY uninterpretable, and meaningless, and cannot be used for any reason, and the testing is a complete waste of their money. and they have to sign a waiver stating that they know it is a waste of their money and the results are meaningless then why do you take their money and offer this service? Do you also test for Radon? Just curious. Quote Link to comment Share on other sites More sharing options...
Steven Hockstein Posted June 13, 2010 Report Share Posted June 13, 2010 People talking on their cell phones and using all of their electronic equipment while worrying about EMF levels from overhead wires is like the people that smoke cigarettes and worry about radon. It adds more risk but it is all bad for us and the combination of exposures increases the odds of illness. Hey I live in NJ-enough said. Quote Link to comment Share on other sites More sharing options...
CaoimhÃn P. Connell Posted June 13, 2010 Report Share Posted June 13, 2010 Thanks Mike! Hello Marc ââ¬â The problem isnââ¬â¢t reflective surfaces (which of course can create some confounding problems), but rather the problem is that measuring EMFs of power lines occurs exclusively in the near field, and therefore, one has no idea what one is actuaslly measuring or how much of it is being measured. As the name suggests, an EMF has two components, an electrical field and a magnetic field. At a point source, these two components are garbled and as one get further away from the point source, the two fields sync up and become a traverse wave wherein the magnetic field and the electric field are perpendicular. As such, in the far field, one can measure the power density and report it with confidence (even where there are reflective surfaces). However, closer to the point of generation, the two fields are not generally in phase and the fields can vary WILDY in magnitude, direction and mutual angular relationship over extremely short distances . Therefore, it raises a very serious question about what a measuring device (an antenna) placed in the field is actually measuring and therefore, there is no way to convert what is being measured into absorbed power (the biologically important aspect). If memory serves, the rule of thumb is that one should be at least 10 times the lambda before making confident E/H (also called E/B) field measurements. OK, since the shortest lambda of the field from a power line is about 10,000 m, that means one has to be several miles away from the home (the powerline being measured) to be confident about what is even being measured. (Try to explain to the home owner why you are in a Starbucks in another city but billing her for measuring the EMFs in her home... ) The school bus parked down the road (or the delivery van driving by), or the massive node centered on the house from another power line 40 miles away, are just minor confounders by comparison. The way we get around it is we tell the client we will faithfully report what the dial on the meter reads, but we wont tell them what it means or what it is measuring (in any event the number on the meter will be completely different one foot way in any direction, or five minute later in the same spot, or in a different (polarized) direction at the same time in the same location.) By the way, we are getting snow, but I want to sit on my deck with a cigar. Cheers! CaoimhÃn P. Connell Forensic Industrial Hygienist www.forensic-applications.com (The opinions expressed here are exclusively my personal opinions and do not necessarily reflect my professional opinion, opinion of my employer, agency, peers, or professional affiliates. The above post is for information only and does not reflect professional advice and is not intended to supercede the professional advice of others.) AMDG Quote Link to comment Share on other sites More sharing options...
Terence McCann Posted June 13, 2010 Author Report Share Posted June 13, 2010 Whenever I perform residential EMF tests, the client MUST sign a waiver acknowledging that I told them the test results are COMPLETELY uninterpretable, and meaningless, and cannot be used for any reason, and the testing is a complete waste of their money. Cheers! CaoimhÃn P. Connell Forensic Industrial Hygienist www.forensic-applications.com CaoimhÃn, I have to ask... If you feel that: test results are COMPLETELY uninterpretable, and meaningless, and cannot be used for any reason, and the testing is a complete waste of their money. and they have to sign a waiver stating that they know it is a waste of their money and the results are meaningless then why do you take their money and offer this service? Do you also test for Radon? Just curious. Bump as CaoimhÃn might have missed the post. Quote Link to comment Share on other sites More sharing options...
Marc Posted June 13, 2010 Report Share Posted June 13, 2010 The problem isnââ¬â¢t reflective surfaces (which of course can create some confounding problems), but rather the problem is that measuring EMFs of power lines occurs exclusively in the near field, and therefore, one has no idea what one is actuaslly measuring or how much of it is being measured. I've not trying to engage in a tit for tat but, just to be clear, EMF field strength is proportional to the inverse of the square of the distance from the point of measurement to the source. In the case of a straight one dimensional antenna (straight run of power line), that 'distance' is measured perpendicular to the line. As the name suggests, an EMF has two components, an electrical field and a magnetic field. At a point source, these two components are garbled and as one get further away from the point source, the two fields sync up and become a traverse wave wherein the magnetic field and the electric field are perpendicular. As such, in the far field, one can measure the power density and report it with confidence (even where there are reflective surfaces). However, closer to the point of generation, the two fields are not generally in phase and the fields can vary WILDY in magnitude, direction and mutual angular relationship over extremely short distances . Therefore, it raises a very serious question about what a measuring device (an antenna) placed in the field is actually measuring and therefore, there is no way to convert what is being measured into absorbed power (the biologically important aspect). Propagating waves in free space always have electric and magnetic components. Electric waves cannot exist without a magnetic companion and vice versa. This is a fundamental property of electrical theory and forms the foundation for everything that follows in wave propagation in free space. The electric and magnetic components of a wave are always exactly perpendicular to each other and both are exactly perpendicular to the direction of propagation regardless of the distance from the source. CaoimhÃn, I'm a great admirer of your work but your descriptions given in this thread seem to indicate that your instructor may have gotten wave propagation in free space mixed up with wave guides and conductors carrying currents. They are intimately related but different. In your post, I think you may have referred to a principle called 'standing waves' and that principle is used to describe the relationship between antenna length and wavelength as it affects the impedance (properties) of the antenna. Just my opinion, of course. It's been 24 years since I finished school but I'll see if I can unearth the relevant textbooks to support my post. Marc Quote Link to comment Share on other sites More sharing options...
CaoimhÃn P. Connell Posted June 13, 2010 Report Share Posted June 13, 2010 CaoimhÃn, I have to ask... If you feel that: test results are COMPLETELY uninterpretable, and meaningless, and cannot be used for any reason, and the testing is a complete waste of their money. and they have to sign a waiver stating that they know it is a waste of their money and the results are meaningless then why do you take their money and offer this service? Hi Terry! As consulting scientists, itââ¬â¢s our job. People ask us to measure various physical entities for a fee and we do so. As such, in accordance with good scientific and Industrial Hygiene practices and procedures, prior to performing the work, our policy is to establish parameters known as Data Quality Objectives (DQOs). DQOs describe the error, accuracy and precision of the parameters being measured. The DQOs also describe the limitations of the data, the application of the data, confidence, comparability and completeness of the data. All this is done before we collect any kind of sample or perform any kind of test. The DQOs also describe the ability of the testing to answer the hypothesis that is being challenged. This is standard for all our work, regardless of whether we are measuring pyrethrin exposures in an home, or exposures to Class IV lasers in a factory, or alpha radiation at a radium site. Practically, EMFs are no different than any other parameter we measure, for example, if we are going into a factory to measure exposures to noise levels or airborne benzene levels, before the work is done the client is made aware of the limitations, DQOs, and other applicable parameters, (and the costs involved with doing the work) and they are required to sign a standard Service Agreement acknowledging the conditions of work. At that point, they are welcome to not sign (in which case we wonââ¬â¢t do the work) or sign the agreement, and then we will perform our contractual obligations for the agreed fee. Do you also test for Radon? Just curious. Yes of course, itââ¬â¢s our job. Just a few months ago, for example I was asked by a branch of the US Government to measure radon exposures in a mine shaft that was approximately one half mile long and was dug into the side of a mountain and wherein workers would be working shift work over the course of three continuous months. Our job was to estimate the anticipated alpha doses received and then to design engineering controls to mitigate the exposures. Hi Marc! Time to brush off the old books my friend! The inverse suqare law is applicable only in far field. I didn't read all the posts in detail but someone referenced some NRC or other study and HORRIBLY misinterpreted the findings. There is no evidence that EMFs from power lines or home electrical appliances etc, increases the risk of cancer. I know, I know, there's a new "report" that cell phones... blah, blah blah... until I see legitimate epidemiological studies reported in legitimate peer reviewed journals, I gotta just stick to the science. The science says - No hazard (as field strungths seen in residences). Cheers! CaoimhÃn P. Connell Forensic Industrial Hygienist www.forensic-applications.com (The opinions expressed here are exclusively my personal opinions and do not necessarily reflect my professional opinion, opinion of my employer, agency, peers, or professional affiliates. The above post is for information only and does not reflect professional advice and is not intended to supercede the professional advice of others.) AMDG Quote Link to comment Share on other sites More sharing options...
Terence McCann Posted June 13, 2010 Author Report Share Posted June 13, 2010 CaoimhÃn, I have to ask... If you feel that: test results are COMPLETELY uninterpretable, and meaningless, and cannot be used for any reason, and the testing is a complete waste of their money. and they have to sign a waiver stating that they know it is a waste of their money and the results are meaningless then why do you take their money and offer this service? Hi Terry! As consulting scientists, itââ¬â¢s our job. People ask us to measure various physical entities for a fee and we do so. As such, in accordance with good scientific and Industrial Hygiene practices and procedures, prior to performing the work, our policy is to establish parameters known as Data Quality Objectives (DQOs). DQOs describe the error, accuracy and precision of the parameters being measured. The DQOs also describe the limitations of the data, the application of the data, confidence, comparability and completeness of the data. All this is done before we collect any kind of sample or perform any kind of test. The DQOs also describe the ability of the testing to answer the hypothesis that is being challenged. This is standard for all our work, regardless of whether we are measuring pyrethrin exposures in an home, or exposures to Class IV lasers in a factory, or alpha radiation at a radium site. You're a pisser CaoimhÃn. You ever think of running for office? You would do well. From a previous post: Whenever I perform residential EMF tests, the client MUST sign a waiver acknowledging that I told them the test results are COMPLETELY uninterpretable, and meaningless, and cannot be used for any reason, and the testing is a complete waste of their money. You would be surprised how many people sign the waiver. The technical rebuttal: People ask us to measure various physical entities for a fee and we do so. As such, in accordance with good scientific and Industrial Hygiene practices and procedures, prior to performing the work, our policy is to establish parameters known as Data Quality Objectives (DQOs). DQOs describe the error, accuracy and precision of the parameters being measured. The DQOs also describe the limitations of the data, the application of the data, confidence, comparability and completeness of the data. All this is done before we collect any kind of sample or perform any kind of test. The DQOs also describe the ability of the testing to answer the hypothesis that is being challenged. This is standard for all our work, regardless of whether we are measuring pyrethrin exposures in an home, or exposures to Class IV lasers in a factory, or alpha radiation at a radium site. You're a funny guy CaoimhÃn - actually I like you. A snifter of Cognac and a few Montecristo Edmundo's would make for an entertaining evening. Quote Link to comment Share on other sites More sharing options...
Bain Posted June 14, 2010 Report Share Posted June 14, 2010 The problem isnââ¬â¢t reflective surfaces (which of course can create some confounding problems), but rather the problem is that measuring EMFs of power lines occurs exclusively in the near field, and therefore, one has no idea what one is actuaslly measuring or how much of it is being measured. I've not trying to engage in a tit for tat but, just to be clear, EMF field strength is proportional to the inverse of the square of the distance from the point of measurement to the source. In the case of a straight one dimensional antenna (straight run of power line), that 'distance' is measured perpendicular to the line. As the name suggests, an EMF has two components, an electrical field and a magnetic field. At a point source, these two components are garbled and as one get further away from the point source, the two fields sync up and become a traverse wave wherein the magnetic field and the electric field are perpendicular. As such, in the far field, one can measure the power density and report it with confidence (even where there are reflective surfaces). However, closer to the point of generation, the two fields are not generally in phase and the fields can vary WILDY in magnitude, direction and mutual angular relationship over extremely short distances . Therefore, it raises a very serious question about what a measuring device (an antenna) placed in the field is actually measuring and therefore, there is no way to convert what is being measured into absorbed power (the biologically important aspect). Propagating waves in free space always have electric and magnetic components. Electric waves cannot exist without a magnetic companion and vice versa. This is a fundamental property of electrical theory and forms the foundation for everything that follows in wave propagation in free space. The electric and magnetic components of a wave are always exactly perpendicular to each other and both are exactly perpendicular to the direction of propagation regardless of the distance from the source. CaoimhÃn, I'm a great admirer of your work but your descriptions given in this thread seem to indicate that your instructor may have gotten wave propagation in free space mixed up with wave guides and conductors carrying currents. They are intimately related but different. In your post, I think you may have referred to a principle called 'standing waves' and that principle is used to describe the relationship between antenna length and wavelength as it affects the impedance (properties) of the antenna. Just my opinion, of course. It's been 24 years since I finished school but I'll see if I can unearth the relevant textbooks to support my post. Marc I don't think I understood one bit of that. Uh . . . which has everything to do with me and nothing to do with Marc's brain or communication skills. Quote Link to comment Share on other sites More sharing options...
Terence McCann Posted June 16, 2010 Author Report Share Posted June 16, 2010 To clarify a bitâ⬦ The reason I started Radon testing was initially due to demand, that and the fact that I thought it would add to the bottom line. After going through initial training for licensing though I gained a much better insight into the ââ¬Åinner workingsâ⬠Quote Link to comment Share on other sites More sharing options...
Bain Posted June 16, 2010 Report Share Posted June 16, 2010 To clarify a bitâ⬦ The reason I started Radon testing was initially due to demand, that and the fact that I thought it would add to the bottom line. After going through initial training for licensing though I gained a much better insight into the ââ¬Åinner workingsâ⬠Quote Link to comment Share on other sites More sharing options...
Terence McCann Posted June 16, 2010 Author Report Share Posted June 16, 2010 For the record, I think you're swell. You're a good friend John. Quote Link to comment Share on other sites More sharing options...
Inspectorjoe Posted June 16, 2010 Report Share Posted June 16, 2010 Be careful how hard you push, Terry - you might end up with deputy Connell accusing you of having multiple DUI's. http://www.agentsonline.net/forums/ubbt ... 232/7.html Quote Link to comment Share on other sites More sharing options...
kurt Posted June 16, 2010 Report Share Posted June 16, 2010 Yes, I think you're swell too. Unnecessarily peevish replies are burdensome, and I have no idea why it happens. Quote Link to comment Share on other sites More sharing options...
Inspectorjoe Posted June 16, 2010 Report Share Posted June 16, 2010 I guess the unnecessarily peevish reply was mine. Actually, I considered it a kind of public service, aimed at the unenlightened. Recognizing patterns can be very enlightening. Quote Link to comment Share on other sites More sharing options...
kurt Posted June 16, 2010 Report Share Posted June 16, 2010 Joe, no it wasn't. I think you're swell too. Quote Link to comment Share on other sites More sharing options...
Inspectorjoe Posted June 16, 2010 Report Share Posted June 16, 2010 Ah, all is well in the world again. I tend to jump to conclusions. Not a good trait for an inspector! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.