OTOH ATE equipment is used to measure as little as pico amp bias current all connections made via relay. I never saw a significant issue except end of life (100's of thousands of operations). These problems would be intolerable in any manufacturing environment.
Only if it is in phase. In general, it won't be.Joe Rasmussen said:
Obviously too hard for you to understand. I will ask again, have you ever heard of complex numbers? Have you ever noticed real engineers using them and wondered why they do this?
Driving force is proportional to current at a particular frequency. Output is not so simple.
Ah, the dreaded time smearing. Classic FUD.
Why do you persist in pushing error which we have corrected time and time again? Repeating something which is untrue does not make it become true.
You don't seem able to grasp the simple truth that a typical speaker, designed for a voltage source, simply needs an amplifier with low distortion voltage amplification and a low and reasonably linear output impedance.
I have no explanation, but the need for 'wetting' relay contacts is found in some communications equipment. Why it is sometimes needed and sometimes not I do not know. I have seen descriptions of problems caused when it has been omitted in cheaper amateur equipment, so the user has to add it himself to solve the problem.scott wurcer said:
DF
I was trying to keep coherers out of the conversation! An interesting historical gizmo still finding use in some way out experiments.
As to using a wetting voltage it applies also to some polarized capacitors.
As beaten to death in audio once conduction occurs additional wetting may not be needed. Although as I measured and mentioned quite a bit back removing and reinserting connectors may clean them enough for folks doing cable tests by ear to over estimate a new cables change in perceived quality.
Pavel,
Having a degree does not guarantee competance. Your degree is in electro acoustics yet you play with high voltage. Now it seems likely the field work with high voltage will weed out those who really did not get it.
My experience is that at major institutions faculty do research and base the curriculum on what they believe is important now and in the future while still covering the basics. At a primarily teaching institution the faculty may just teach what they learned when earning their degrees. So fundamentals will usually be covered but not much current work.
When I started EE classes at a way young age there were those glowing thingies. Yet they were not even covered in my university courses.
Also not covered were things like AC power distribution systems or anything old enough to be considered solved and reduced to technician level systems.
Magnetics became an elective course not a main curriculum one. Today transducers are an alternate year elective at my local university.
I have to assume even with your inappropriate degree you are competent in high voltage work as you are still here!
Now as to your system measurements I find it scary that even with litz wire at such a short distance you are already showing high frequency loss.
When I did my first stadium all HF loss was assumed to be from acoustical issues. I have yet to see in any professional articles or texts mention of cable losses. At that same first project I did do measurements that showed for cable runs under 250M that the maximum code friendly cable had less loss than using transformers over the frequency range obtainable in a large venue. Back then there were several folks offering high power rated audio transformers. Very few today even though the current code has reduced the maximum cable thickness. (I need to write a letter to that code committee.)
I was trying to keep coherers out of the conversation! An interesting historical gizmo still finding use in some way out experiments.
As to using a wetting voltage it applies also to some polarized capacitors.
As beaten to death in audio once conduction occurs additional wetting may not be needed. Although as I measured and mentioned quite a bit back removing and reinserting connectors may clean them enough for folks doing cable tests by ear to over estimate a new cables change in perceived quality.
Pavel,
Having a degree does not guarantee competance. Your degree is in electro acoustics yet you play with high voltage. Now it seems likely the field work with high voltage will weed out those who really did not get it.
My experience is that at major institutions faculty do research and base the curriculum on what they believe is important now and in the future while still covering the basics. At a primarily teaching institution the faculty may just teach what they learned when earning their degrees. So fundamentals will usually be covered but not much current work.
When I started EE classes at a way young age there were those glowing thingies. Yet they were not even covered in my university courses.
Also not covered were things like AC power distribution systems or anything old enough to be considered solved and reduced to technician level systems.
Magnetics became an elective course not a main curriculum one. Today transducers are an alternate year elective at my local university.
I have to assume even with your inappropriate degree you are competent in high voltage work as you are still here!
Now as to your system measurements I find it scary that even with litz wire at such a short distance you are already showing high frequency loss.
When I did my first stadium all HF loss was assumed to be from acoustical issues. I have yet to see in any professional articles or texts mention of cable losses. At that same first project I did do measurements that showed for cable runs under 250M that the maximum code friendly cable had less loss than using transformers over the frequency range obtainable in a large venue. Back then there were several folks offering high power rated audio transformers. Very few today even though the current code has reduced the maximum cable thickness. (I need to write a letter to that code committee.)
Yes they use sealed relays. Sometimes mercury wetted others gold or other special alloys crossbar contacts. Unfortunately there are problems with using audio systems in a sealed oxygen free environment.
It is actually the sulfur in the air that causes the problems. Silver oxide is actually a good conductor. Sulfur of course mainly gets into the air from burning coal.
In all the R&D and physics labs I have been in I have never seen such a fuss over these issues as here.
I certainly have never observed any mysterious dead zones in sensitive measurements.
Relay A ≠ Relay B
I have recently seen some relays from Asia which have unstable high initial resistance (~1Ω) and fail within tens or hundreds of cycles. I disassembled one and it had NO PLATING on a brass armature. On the other hand I have some Clare hermetically sealed relays from the 1970s which were in operation for 20 years and still today show less than 10 mΩ contact resistance. Cost difference? Most likely 200:1 or more, but to repeat: Relay A ≠ Relay B
Howie
Thank you for making the point I was making.
Now please explain:
F = BLi
So what is F in this instance?
And somebody (me) should tell "DF" that complex numbers are not needed to explain something that can already be explained by Ohm's Law.
Oh, I will make it easier for you to answer above, what makes a cone move?
They are if you want to explain it properly, which you don't seem interested in.
It means you are going round and round in circles until you get sinbinned again not listening to anyone. Not sure why they bother as this is about the 6th round of this with zero progress.
I think the fixation with Shalco switches and reportedly the fact that you may have to rotate them a few clicks clockwise and then anti clockwise to clean the contacts may have scared some people.
Its important however to note that in the southern hemisphere, you must rotate anti-clockwise first, and then clockwise. If you don't do it this way it will affect the sound and this is probably why in some areas the Shalco's have a bad name. (No doubt Dan of course will immediately be able to hear this as well).
For my part, I just use sealed (i.e. encapsulated relays). Stuff I built 15 years ago still works flawlessly. However, I rotate the relay by 180 degrees in the vertical plane, wait 10 seconds, and then rotate it back to its original position. I do this with all my relays before soldering them into the PCB. Again, in the southern hemisphere, you should go in the opposite direction for best performance.
Oh, and don't forget to bless the relays as they get shipped out.
Its important however to note that in the southern hemisphere, you must rotate anti-clockwise first, and then clockwise. If you don't do it this way it will affect the sound and this is probably why in some areas the Shalco's have a bad name. (No doubt Dan of course will immediately be able to hear this as well).
For my part, I just use sealed (i.e. encapsulated relays). Stuff I built 15 years ago still works flawlessly. However, I rotate the relay by 180 degrees in the vertical plane, wait 10 seconds, and then rotate it back to its original position. I do this with all my relays before soldering them into the PCB. Again, in the southern hemisphere, you should go in the opposite direction for best performance.
Oh, and don't forget to bless the relays as they get shipped out.
Because F stand for Fortress?
Seems an equation from hell, everybody is running away?
Would you like to have a go at it. You know, it is called physics, or maybe you are not a fan of Faraday?
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