OT: Piezo Vibration Sensor
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Posts: 46,084
Does anyone have any suggestions regarding smoothing the output of a piezo
vibration sensor attached to a back massager? My setup right now is a LDT
Piezo film vibration sensor connected to an adc0831 via a full bridge
rectifier and a 22uf filtering cap on the A/D input. I have the stamp
averaging ten samples from the ADC but the reading still bounces around
some. The application notes from Measurement Specialties do not go into too
much detail other than they use a “charge amplifier”. Is there a better
method to interface the sensor to a stamp? I took a guess at using the
rectifier, and I have no idea if my cap is the right size or not. Any
advice will be appreciated. Thank you.
Jeff
[noparse][[/noparse]Non-text portions of this message have been removed]
vibration sensor attached to a back massager? My setup right now is a LDT
Piezo film vibration sensor connected to an adc0831 via a full bridge
rectifier and a 22uf filtering cap on the A/D input. I have the stamp
averaging ten samples from the ADC but the reading still bounces around
some. The application notes from Measurement Specialties do not go into too
much detail other than they use a “charge amplifier”. Is there a better
method to interface the sensor to a stamp? I took a guess at using the
rectifier, and I have no idea if my cap is the right size or not. Any
advice will be appreciated. Thank you.
Jeff
[noparse][[/noparse]Non-text portions of this message have been removed]
Comments
What is the frequency of the pizeio output? A 22 uF capacitor
is good for low frequencies, but we use a 0.1 uF and sometimes a 500 pF
silver mica to bypass our circuits. If you have an oscilloscope, you
can look across the cap and see if it's filtering correctly. If not,
put your Voltmeter across the cap, put it on ac Volts, and turn up the
sensitivity to see how much ripple is there. The Voltmeter (guessing
here, but usually it works) should go up to 1 kHz I would think.
Original Message
From: Jeff Mitchell [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=dPOtjdnm4D9xImrzmQdtSNz6APDoGXDXcRPxRuA3cgLQCCQcN7ViIsc-hIhTHr5bP21fRBNANApTBVrfL1fbz45-Dvh52Ouk]JMitchell@G...[/url
Sent: Tuesday, February 25, 2003 10:18 AM
To: Basicstamps@Yahoogroups. Com
Subject: [noparse][[/noparse]basicstamps] OT: Piezo Vibration Sensor
Does anyone have any suggestions regarding smoothing the output of a
piezo vibration sensor attached to a back massager? My setup right now
is a LDT Piezo film vibration sensor connected to an adc0831 via a full
bridge rectifier and a 22uf filtering cap on the A/D input. I have the
stamp averaging ten samples from the ADC but the reading still bounces
around some. The application notes from Measurement Specialties do not
go into too much detail other than they use a "charge amplifier". Is
there a better method to interface the sensor to a stamp? I took a guess
at using the rectifier, and I have no idea if my cap is the right size
or not. Any advice will be appreciated. Thank you.
Jeff
[noparse][[/noparse]Non-text portions of this message have been removed]
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and is the normal interface required for the piezo accelerometer. It may be
possible to "kludge" an interface with some high impedance active device for
some relativistic measurement, but unless normal low resistive and
capacitive loading requirements are met your sensitivity will greatly suffer
and absolute sensitivity (scale factor) will not be what is published for
your device. Users wanting to avoid the requirements of the charge
amplifier and the necessary coax cabling between accelerometer and charge
amplifier should use the type of accelerometer where the charge amplifier is
built into the device and the output can be interfaced as most other sensors
with a voltage output. If the charge amplifier was indicated as a
requirement for your sensor, then it is not of the latter type.
It may be that some of your erratic behavior is due to changes in the
capacitance of the wiring between the accelerometer and your interface as
the measurement proceeds. Even with the use of proper cable and charge
amplifier, if the cable is somewhat damaged, it can provide for erratic
results, in my experience with them in the distant past.
*******************************
Daryl B. McMurrin
R&D Engineer
Gyration, Inc.
12930 Saratoga Ave., Bldg. C
Saratoga, CA 95070
Phone: (408) 973-7056
Fax: (408) 255-8762
Is there a gyro in your mouse?
Original Message
From: Jeff Mitchell [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=I8exUsYiw2UUDUhlDoOSlWwaQZB0C4UjYwA0UqzyPSOASMtX1UXyo3V7RXtLfpbZk5AMzh9IuAwlgg9nvt3TgxXXiCbQ]JMitchell@G...[/url
Sent: Tuesday, February 25, 2003 7:18 AM
To: Basicstamps@Yahoogroups. Com
Subject: [noparse][[/noparse]basicstamps] OT: Piezo Vibration Sensor
Does anyone have any suggestions regarding smoothing the output of a piezo
vibration sensor attached to a back massager? My setup right now is a LDT
Piezo film vibration sensor connected to an adc0831 via a full bridge
rectifier and a 22uf filtering cap on the A/D input. I have the stamp
averaging ten samples from the ADC but the reading still bounces around
some. The application notes from Measurement Specialties do not go into too
much detail other than they use a "charge amplifier". Is there a better
method to interface the sensor to a stamp? I took a guess at using the
rectifier, and I have no idea if my cap is the right size or not. Any
advice will be appreciated. Thank you.
Jeff
[noparse][[/noparse]Non-text portions of this message have been removed]
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