Vibration Monitor (Hyde, Wanttaja?)

Love to. You got my address?

Jim




"George A. Graham" wrote in message
...

Jim,

I have a Memsic demo board, which displays LEDS on two axis with
their tilt and motion sensor.

I am done with it, would you like to play with it?

George Graham
RX-7 Powered Graham-EZ, N4449E
Homepage http://bfn.org/~ca266

"RST Engineering" wrote in message
...
Strangely enough, that is what I *DID* for a living when Spectral Dynamics
was the industry leader in machinery diagnostics. Unfortunately, my job
was the circuit design, not the diagnostics itself, so all I concerned
myself with was the black box that took a defined input and produced a
defined output. There are times I wish that I had transferred to the
applications department. They were the ones that seemed to have the most
fun (and the most three martini Friday lunches).


Jim



LOL.
I've been an engineer designing in the dark many times.
Fortunately at Bently, there is a large effort to train engineers in
diagnostics.
Then we can use personal experience in addition to requirements documents
when designing a new product.
Or, at least, we can determine if requirements make sense!

Adam

"sleepy6" wrote in message
...

Of course this simple setup will not show side to side movement. That
would require a second proximity detector 90 degrees from the first
one. The 2 signals would require integration but would then show all
movement in the rotational plane with the proper signal processing and
calibration.


Exactly. This two-dimensional shaft path is called an orbit.

Adam

Understood. What I started out to do (and still plan on doing) is to have a
device that will stay permanently mounted to the engine that can be
calibrated (adjusted, signed, pick a verb) when the engine is known to be
good and light a "your engine is about to come apart" lamp at the
appropriate time.

What this group seems to be leaning toward is a lab quality device that will
allow for sophisticated diagnostics. That ain't the thrust of my Kitplanes
columns. KISS and BURP.

Jim

"RST Engineering" wrote in message
...
Understood. What I started out to do (and still plan on doing) is to have
a device that will stay permanently mounted to the engine that can be
calibrated (adjusted, signed, pick a verb) when the engine is known to be
good and light a "your engine is about to come apart" lamp at the
appropriate time.

What this group seems to be leaning toward is a lab quality device that
will allow for sophisticated diagnostics. That ain't the thrust of my
Kitplanes columns. KISS and BURP.

Jim


As is tradition, we tend to get off topic ;-)
I think you can accomplish this using the methods discussed.
Mount 2 proximity probes 90 degrees apart.
Calibrate the readings for normal low vibrations (be sure to account for any
nonlinearities in the probe).
Design the circuit to trip the buzzer/lamp when the vibration exceeds the
normal level.
You may need some analog circuitry to help (gain, etc).
But you don't need to get much fancier than that.

Adam

Proximity probes? Or accelerometers?

I understand about the analog circuitry and actually plan on making a five
or six channel filter at each of the possible resonance points relative to
the fundamental ... and then strobing the filters to light a "normal",
"low", "high" lamp for each channel.

Jim




As is tradition, we tend to get off topic ;-)
I think you can accomplish this using the methods discussed.
Mount 2 proximity probes 90 degrees apart.
Calibrate the readings for normal low vibrations (be sure to account for
any nonlinearities in the probe).
Design the circuit to trip the buzzer/lamp when the vibration exceeds the
normal level.
You may need some analog circuitry to help (gain, etc).
But you don't need to get much fancier than that.

Adam

"RST Engineering" wrote in message
...
Yes, all of the below.

Sometimes you drill a hole in a small magnet and use a small screw to hold
it to the propeller backing plate. Sometimes you use a strip of
reflective
tape on the prop itself. Sometimes you use a pulse from the #1 magneto
lead.

Jim

This guy was talking about a notch and proximity detector for the phase
detection. I know about all of the things you mentioned, but the proximity
detector's workings are new to me.
--
Jim in NC

I would use proximity probes if you are primarily going to measure
vibration.
They are also the best choice if you are going to notch the shaft and do
phase measurment.
I'm not sure about other venders' prox probes, but the one's I'm used to
have a linear range.
The phase measurment can be gained so that it rails one way when over the
notch and rails the other way when not, so you don't have to worry about the
linear range. As for vibration measurments, you will have to make sure that
you stay in the linear range of the probe.

I want to make sure I understand what you meant by having a filter at the
resonance points.
Are you only going to measure vibration at resonance (i.e. bandpass)?
Or, are you NOT going to measure at resonance (i.e. notch filter)?
Keep in mind other events may cause vibration, such as impulse, rub, etc,
which will likely occur synchronous to the shaft, and have nothing to do
with resonance.
This is where a phase reference may be handy because you could determine if
it is happening 1X/rev, 2X/rev, etc.
OR, are you assuming that an impulse/rub event will excite the case at the
resonance frequency?

At any rate, what you intend on doing is definitely do-able.
I recommend playing with probes a bit to see what you get.
Sounds like a fun project.
Let me know if there's anything I can offer...

Adam


"RST Engineering" wrote in message
...
Proximity probes? Or accelerometers?

I understand about the analog circuitry and actually plan on making a five
or six channel filter at each of the possible resonance points relative to
the fundamental ... and then strobing the filters to light a "normal",
"low", "high" lamp for each channel.

Jim




As is tradition, we tend to get off topic ;-)
I think you can accomplish this using the methods discussed.
Mount 2 proximity probes 90 degrees apart.
Calibrate the readings for normal low vibrations (be sure to account for
any nonlinearities in the probe).
Design the circuit to trip the buzzer/lamp when the vibration exceeds the
normal level.
You may need some analog circuitry to help (gain, etc).
But you don't need to get much fancier than that.

Adam

In article ,
Morgans wrote:

"RST Engineering" wrote in message
...
Yes, all of the below.

Sometimes you drill a hole in a small magnet and use a small screw to hold
it to the propeller backing plate. Sometimes you use a strip of
reflective
tape on the prop itself. Sometimes you use a pulse from the #1 magneto
lead.

Jim

This guy was talking about a notch and proximity detector for the phase
detection. I know about all of the things you mentioned, but the proximity
detector's workings are new to me.

Think of a proximity detector as 'ultra short-range radar'. grin
It may use reflected RF energy, or 'optical'.

where the 'excursions' you're trying to measure are smaller than the
wavelength of the measuring 'beam', you can use simple phase-shift
between outgoing and returning signal, to determine distance.

where the distance is much larger than the wavelength, you have to
impress a carrier on the beam, and measure phase-shift in the carrier
frequency. this gets an 'approximate' distance, that can be further
refined by phase angle measurements of the beam itself.

Capacitance tracking is also a possible approach.
and/or "Hall effect".

These can get 'messy', due to inherent non-linearity in the technology,
that has to be compensated for, in 'reading' the signals.

Capacitance tracking works best where there are *very*small* vibrations
involved, and a very _smooth_ surface to measure against. The technique
is capable of mapping individual atoms/molecules in a crystal lattice.
Scientific American had a write-up -- at least 15 years ago -- about
a new 'super microscope' (successor generation to the scanning electron
microscope) that worked in that manner. a _very_fine_ 'needle' was
carefully moved, raster-style, across the object being 'scanned', and
the capacitance changes between the needle and the object were mapped.

"Robert Bonomi" wrote in message
...
In article ,
Morgans wrote:

"RST Engineering" wrote in message
...
Yes, all of the below.

Sometimes you drill a hole in a small magnet and use a small screw to
hold
it to the propeller backing plate. Sometimes you use a strip of
reflective
tape on the prop itself. Sometimes you use a pulse from the #1 magneto
lead.

Jim

This guy was talking about a notch and proximity detector for the phase
detection. I know about all of the things you mentioned, but the
proximity
detector's workings are new to me.

Think of a proximity detector as 'ultra short-range radar'. grin
It may use reflected RF energy, or 'optical'.

where the 'excursions' you're trying to measure are smaller than the
wavelength of the measuring 'beam', you can use simple phase-shift
between outgoing and returning signal, to determine distance.

where the distance is much larger than the wavelength, you have to
impress a carrier on the beam, and measure phase-shift in the carrier
frequency. this gets an 'approximate' distance, that can be further
refined by phase angle measurements of the beam itself.

Capacitance tracking is also a possible approach.
and/or "Hall effect".

These can get 'messy', due to inherent non-linearity in the technology,
that has to be compensated for, in 'reading' the signals.

Capacitance tracking works best where there are *very*small* vibrations
involved, and a very _smooth_ surface to measure against. The technique
is capable of mapping individual atoms/molecules in a crystal lattice.
Scientific American had a write-up -- at least 15 years ago -- about
a new 'super microscope' (successor generation to the scanning electron
microscope) that worked in that manner. a _very_fine_ 'needle' was
carefully moved, raster-style, across the object being 'scanned', and
the capacitance changes between the needle and the object were mapped.



Actually, the proximity probes I am familiar with work on the "eddy current"
principle.
That is, RF energy is directed at the shaft through a coil. Some of the
energy is lost into the shaft in the eddy currents.
The energy that is coupled back into the coil is the measured signal.
Since the amount of energy dissipated in the shaft is proportional to the
distance between the shaft and probe, the result is a displacement
measurment.

Adam