Hi I’m a young tuner with a question regarding Peterson strobe tuner 490-st.

I live in the northern part of the US and frequently keep the tuning equipment in my car’s trunk.

Seeing how it is nearing winter I am wondering if the Peterson strobe tuner 490-st. will tune accurately (not flat) when it is cold, or if I should be bringing it in whenever possible.

I ask because according to the electronic tuner the last 4 pianos I have tuned were sharp.

Thanks for shedding any light on this issue.

Thanks

I wonder about this myself. Perhaps not the tuner itself, but the microphone, being a transducer, which is mechanical device at least in part, could be affected. I don't use such things, so I can't tell.

The mic will record whatever frequency it is exposed to. It can't change any frequencies, it's just a transducer. The Peterson may be stable or unstable, depending on what technology is used to generate the frequencies for tuning. Every machine which uses a quartz as a time base will be very precise at every temperature, a very old-fashioned machine with RC-networks won't. So most modern ETD will be ok with any temperatures they are specified to work with. If it's really too cold they won't work, but if they work they will be precise.

Jens

Any moving part can react differently according to the temperature. That includes microphones. Transducers are generally the weakest link in a system.

There's a bit of a discussion here: Microphone Handbook.

In my 20 years in Chicago, I took my tools inside when the temp got lower than 35 degrees. I found that if I didn't, everything would condensate when I opened up my tool kit at the first tuning of the day. Moisture would be on my tuning fork, tuning hammer, and everything. The cold would make Elmers and superglues rock hard and they would be useless. Stands to reason the strobe tuner would condensate as well. Take your tuning tools and your ETD inside at night.

That was reason #56 why I moved to Florida!

Sounds like a good plan, i'll be bringing in the tools and tuner from now on
THanks all this is really quite helpful.

With any microphone input frequency and output frequency are equivalent. This is a basic principle of magnetic induction. If you take for instance the very simple magnetic microphone, you'll see that if the membrane vibrates at 440Hz for instance, the coil on the membrane will also vibrate at that speed in the magnetic field created by a magnet and thus an electrical current of the same frequency is induced in that coil. It is not possible that for instance the membrane vibrates at 440Hz and the coil at 441Hz because they are directly coupled. No matter if you'd use a very cheap or very expensive microphone, they will all be precicely the same when it comes to the equivalence of input and output frequency. They are not the same when it comes to the equivalence of input pressure and output voltage on all frequencies. That means a very good microphone would create the same output voltage at all frequencies (given the sound pressure is the same at all frequencies) whereas a cheap one won't. That's why they sound different. And here it could be very well possible that heat or cold could change the frequency range of a mic (the membrane might get stiffer with cold and might not vibrate that easily anymore and thus not create as much output voltage as when at a higher temperature but this will not effect the speed at which the membrane vibrates (as long as it vibrates at all, it vibrates at the speed of the soundwave), only the amplitude, thus the frequency itself is always constant).

Tuning forks are something different. They will react on heat and cold. With heat the metal will expand and the tuning fork will vibrate slower, with cold it will contract and thus vibrate faster.

Jens

It is very possible for the air to vibrate at one frequency and have it cause the movable portion of the microphone to vibrate at a different frequency. That's how a wind instrument works. For that matter, it could happen with the receptors in one's ears, as well, but at least that's the way people hear sound, so it doesn't matter.

The frequency difference may not be very much, but it may be significant compared to the accuracy needed for good tuning. I suspect that this is something that hasn't been studied much, however. I doubt much has been done since Helmholtz discovered that the frequency of a siren is different from the frequency that you would calculate from the rotation of the siren's disk.

It's not possible for a microphone to change the vibration frequency--Jens is correct. Knowledge of the physics involved explains the reason, but is well beyond the scope of this thread.

In other words, you don't know.

It is really quite simple. Frequency is just a count of cycles over a length of time. A microphone may distort the shape of these cycles, but it cannot change the count. If there are 440 cycles in one second, then the electrical signal from the microphone will have 440 wiggles in one second. How could it have anything else? A microphone is not a frequency standard. It merely transfers the sound signal to circuitry that compares the frequency against a standard - probably a quartz crystal oscillator. You can question the effect of temperature on the crystal oscillator, but the characteristics of the microphone are irrelevant.

Robert Scott
Real-Time Specialties

The same logic says that there is no such thing as inharmonicity.

To get back to the question, remember that he is asking about a Peterson tuner.... that's an electo-MECHANICAL machine, the one with the spinning disk. I would imagine that there might be some consequences for trying to use that right out of cold trunk!

But as to finding pianos that are sharp, do you know the current humidity vs. the humidity at the time of the last tuning? If it is higher now, the pitch will probably be sharp. No surprise there.

This is the most useful observation, if also the most obvious. I would also ask how the Peterson strobe is being used for piano tuning; if it is used only for measuring pitch at say, A440, that is one thing. If it is used for tuning, that is quite another matter.

BDB, there is no cause for you to make an unwarranted and untrue statement like that--you owe me an apology. In fact, I do understand the physics and could quote you chapter and verse. If you'd like I can give you book titles and even page numbers where you can find the theory involved. It's because I know it and understand the various subtleties that I know there is no simple way to express all the equations and context necessary to understand this phenomenon is a complete theoretical way.

Again, I must say your comment was really gratuitous and rather nasty. In the future you should stick to the topic at hand and refrain from making ad hominem attacks.

Why should I apologize to you? It's unwarranted and untrue to assume that the explanation is beyond the scope of the thread. That's just a way of saying that you think we are all too stupid to understand. Talk about being gratuitous and nasty! Maybe you owe all[/b] of us an apology.

And no, I don't want chapter and verse. I don't wish to waste my time following dead links and looking up obscure references only to find that you or someone else have misinterpreted or ignored something, like has happened so often on this board before. If you can't explain it so a well-educated person like myself can understand it, then as far as I am concerned, it's because you don't know.

Good God, your hubris is nothing short of amazing! If you've ever studied physics, you know that theoretical explanations can take many pages dense with equations. I have a copy of Leo Beranek's classic text, "Acoustics." His chapters on microphones run for 38 pages, and I can assure you they're anything but light reading. Much of what is discussed in those pages depends on understanding what was presented in the preceeding 138 pages. Much of that material depends on a general understanding of physics, algebra, and calculus. I can only assume someone as well-educated as you proclaim yourself to be knows so much about it that a brief hand-waving exposition will suffice, so here goes.


At its simplest, a microphone can be represented as a lumped, damped, spring-mass system. Such a system can be mathematically represented by a linear differential equation. Someone familiar with physics, math, or engineering would know that a linear system cannot generate frequencies different from any excitation frequency.

Even assuming nonlineary, any distortion would only create frequencies that are the result of so-called harmonic or intermodulation distortion. Harmonic distortion can generate spurious signals at integral multiples of the input signal's frequency. Intermodulation distortion can generate signals at the sum and differences of two or more independent frequency inputs.

None of these potential distortion products could possibly end up very close to the input frequency. In addition, distortion products of even a cheap microphone would be many dB down from the main signal and would not obscure the main signal

This explanation is unsatisfactory to me because I only state a few conclusions without building a theoretical basis. That's why I said that the explanation is beyond this thread. To really do the subject justice would require many, many equations and much science.

And, by the way, I have not misrepresented anything, and would not give you or anyone else dead links. I always try to be very careful when posting in this forum. I always indicate when something is my opinion or if I am unsure of my facts. But, on a subject like this I do know my facts.

So, I say again, you owe me an apology for your insults and false statements as to my knowledge. I don't expect one, and I shall not comment further on this thread. There are any number of people in this forum who can vouch for the soundness of my statements.

I thought Robert Scott explained it very well. Even if you assume the cold air would have a stiffening effect on the diaphram - It makes sense the diaphram would still vibrate at the frequency it hears, but perhaps less efficiently so and probably with the distortion Roy speaks about.

Back to the cold question - I wouldn't expect a strobe tuner with a mechanical wheel to be accurate when exposed to very cold weather. Nor is a tuning fork. Even if I drove for an hour to get to my first stop, the heat in the car would not warm my tools. Better to keep them warm inside at night. (Don't forget them in the morning) been there. done that. not funny.

Probably the best thing to do (besides just keeping the sucker warm) would be to call Peterson and ask them. I'll bet they know the answer. I've talked to them about a couple unrelated things in the past and they were very friendly and helpful.

in response to the question about do i know the humidity levels at the time of the last tuning - NO i do not, but the 4 pianos I mentioned were likely tuned in the summer.

In response to how is the Peterson strobe tuner is being used.
1. I set A440 with it
2. I use it to help set the equal tempermant.
3. for the rest of the piano I do by ear.

THank you for all these truely insiteful posts.

http://www.petersontuners.com/products/model490st/index.cfm If anyone is interested is the link to the tuner itself.

The manual for the 490ST says that it also uses a quartz crystal reference. The mechanical wheel is locked to that reference by a phased-locked loop. Therefore it will be as accurate and as immune to temperature effects as the quartz crystal itself. If it gets so cold that the bearings freeze up, then the phased-locked loop may fail and the pitch will be way off. But it will not behave like a tuning fork, which gradually changes pitch as the temperature gradually changes. The 490ST system only has two states: perfect and broken.

Robert Scott
Real-Time Specialties

Papageno, I see myself in you, except that I'm not young anymore.

For many years I've tuned by ear with a lot of trial & errors. My perfect pitch did not enhance my ability to tune well, until somebody introduced The Peterson Autostrobe 490ST to me. It improved my tuning by leaps and bounds. Was I happy that it saved my ears from listening to the confusing beats, but it gradually led me to see the optician next door as my eyes strained too much from the aggresive strobe lights.

I do not know Robert Scott until I heard about the Tunelab being a very good and accurate tuning aid, recommended by very very good piano tuners and educators. I followed the link www.tunelab.com and downloaded the free trial. My "leaps and bounds" bounced up to great heights and from that day on I became proud of being a piano tuner (self-made professional).

I still do not know Robert Scott, but because he is the father of Tunelab, I look up at him as my saint. Thanks, Mr. Scott.

P.S.
This is not a paid ad. Just a word from a satisfied customer. And by the way, Tunelab works accurately and intelligently under all kinds of temperatures.


JUNMER

This is funny.
This should be a FAQ.

Junmer makes a good point. Most professional tuners who use ETDs would not recommend a Peterson tuner for piano work. There is no way for this instrument to reflect in its stretch settings the actual inharmonicity curve of the piano being tuned. Tunelab, along with several other high quality ETDs which are well-suited for tuning pianos, do have this capability. It makes all the difference in the quality of the tunings.