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Vibe-Rater

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Reply with quote  #1 
Hi Everyone,

Stupid question alert!

Saturday afternoon and mucking around with my CSI Speedvue.  I know it is very sad...  Thought I would try it on the Dutch family inherited wall clock that I have not been able to throw in the rubbish yet. (trash for all Americans).  See attached.

Speedvue measures 46.43 cpm of the pendulum.  See laser pointer in pic.

I always thought the a clock pendulum would swing at 1 per second....?????

And the counter weight for the ding dong is not installed because I can't stand the ding dong.

I trust the speedvue and the clock keeps time. So is the answer that the pendulum is the driver, no matter what its swinging frequency? The bigger, longer the slower, -- not 1 second related??

Anyway, just thinking and it IS vibration yeahh. rgds





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MarkL

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Nothing sad about it, I had my 9 year old help me balance my wife's cooker hood fan last weekend as it's noise was driving me daft, got it from 12mm/s down to 2.5mm/sec, was well chuffed. I think I've awoken something in the son, he's pointing out rough running things in everyday life since.
Walt Strong

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Reply with quote  #3 
A stop watch can easily replace the expensive SpeedVue for the clock! Digital/analog watch to watch the old clock tick-tock!

Walt
Ron Brook

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Reply with quote  #4 
Correct! The pendulum does not need to have a one second period. Because of different lengths, its all in the gears. Got a better one for you. I have a Gustav Becker Vienna Regulator in my living room. Keeps perfect time. Then I read in the NAWCC that the second hand dial completes its one minute sweep in 46 seconds!?!?
Of course I had never noticed so I timed it...what a rip off, Gustav!! Again, it's all in the gears.😜
Vibe-Rater

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Hi Ron, that makes sense, all in the gears and gravity of course provides the force to just keep the pendulum going.  it was a pretty neat way to play with the Speedvue without having to use any reflective tape.  Do other brands have lasers like this?  Also reminds me of the Harrison in the Greenwich museum of time. He was a carpenter and designed the first chronometer for use at sea where the motion upsets pendulums(sic?) Pickup a copy of the book titled Longtitude for virtually nothing on eBay or Amazon and have a read.  Sounds like you will know about this already. rgds
electricpete

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Reply with quote  #6 

I agree pendulum does not necessarily have to have a 1 second period.

I would also keep an open mind to error associated with non-standard pickup method.  

Personally I'd count the ticks for a minute with a stopwatch.   If it's not close to 46, then we'd start wondering about what could have gone wrong.

Not that it's critical or anything, but it's easy enough to double check.

Vibe-Rater

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Hi EP, I reckon Speedvue is pretty accurate but what is the meaning of pretty...  and accurate..   If I was on a deserted island with ... well .. a Speedvue I would trust its accuracy. rgds






electricpete

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Reply with quote  #8 

I'm not really familiar with speedvue and certainly not familiar with how you set it up to monitor a pendulum.

My concern originated from thinking about how a system intended to monitor a mark on the shaft might get confused monitoring a pendulum.     What is the width of the target (assuming  the laser is looking for a rising edge, the target width is not important for shaft rotating in constant direction but is very important for pendulum reversing direction).  How does the system react when the direction reverses or if the pulses are not equally spaced.

It's not a huge concern. But in 60 seconds it could be ruled out. And I've already spent way more than 60 seconds typing.  That's why I suggested it that way. But you're viewing it from a different angle, knowing more about speedvue and how you monitored this pendulum, so I accept whatever conclusion you come to.

Vibe-Rater

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Reply with quote  #9 
Hi EP, The CSI Speedvue is a really neat device.  it basically is a laser and the device receives a reflection / voltage pulse proportional to the difference between light and dark. Then does an FFT on it and figures out running speed. I think deeper down it takes a time waveform and identifies once per rotation voltage peaks.  Through the 2130 (or 2140) you can adjust the trigger voltage which helped me out recently and was able to trigger on a white manhole cover meaning we did not need to stop machine.

See link.  https://www.youtube.com/watch?v=FSo60xsjD5c This link just popped up when I Googled - so happens I know the presenter, the company he worked for was acquired by GE. Such a pity.  GE management is in the process of applying their wisdom to destroy this part of what they bought. So now they need to sell Commtest but for their service work still use CSI.  But hey.

So I pointed the Speedvue at the edge of the pendulum weight when it was at the extreme swing point, max displacement from center. Which caused a sufficiently large voltage pulse for the 2130 to figure out the swing frequency.

I was only playing around but have used it plenty of times in the field.  Once you have a Speedvue you'll never want to be without one. Monarch has something similar. I think it could be made to cooperate with CSI instrument given the correct cables... but I don't know.  The firmware functions in CSI make all that very easy.  There used to be a TEC brand laser, Rusty knows all about that one. I don't think they make them anymore so Rusty has a collection of them if I remember correctly. James can also fill in on extra Speedvue detail. rgds
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