angular accelerations through accelerometers
angular accelerations through accelerometers
(OP)
I have to measure angular acceleration in a vehicle and since I haven't gyrobox, I have to use two accelerometer placed at known distance. At work I have only accelerometer with +/- 50g full scale. Are they good for the measurements I have to carry out? I'm doubtful, they have a low sensitivy for my need.





RE: angular accelerations through accelerometers
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: angular accelerations through accelerometers
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: angular accelerations through accelerometers
RE: angular accelerations through accelerometers
What are the accelerations you are interested in?
Is it something like a general purpose accelerometer used for vibration analysis? Noise floor of a a few dozen micro-gs depending on frequency, but unsuitable for "low frequency" events.
https://ww
Then there are these kind of interesting comsumer product accelerometers.
http://
A word like "Low" applied to sensitivity in some ways reminds me of my wife's response to my inquiry of how much some some purchased item cost. Her reply is almost certain to be "oh, not very much."
I used to think I simply didn't know any more about the item's price after hearing that answer than I did before. But now I know what it really means is that in a few years the equity line on the house is going to be all tapped out.
RE: angular accelerations through accelerometers
http
has you can see my accelerometers has a sensitivity of 40mV/g.
RE: angular accelerations through accelerometers
What is the shaft speed?
What is the frequency range?
6-degrees is angular displacement, but what is the angular acceleration you expect (max and min) to measure?
Why do you want to measure angular acceleration instead of velocity or displacement?
Not only do the accelerometers have to produce adequate voltage, but the summing amplifier and telemetry system have to handle the signals with minimum noise. I would consider alternative methods such as an angular accelerometer or encoder-F/V system.
Walt
RE: angular accelerations through accelerometers
I have to measure vehicle roll and pitch accelerations. I don't know what should be the maximum roll and pitching angles (but I suppose less than 6 degrees for both of them) and their acceleration values. I need to measure the angular acceleration for finding a correlation with the trasmitted driver acceleration. In the company I work, we haven't an angular accelerometer. What do you mean for encoder f/v system?
thanks
RE: angular accelerations through accelerometers
While it's certainly not impossible to use linear accelerometers, it's nontrivial, since you do not know the center of rotation.
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: angular accelerations through accelerometers
Yes 50g accelerometers are completely inappropriate for that application. 2-3g is more like it. You will also need good low frequency response, 0.3 Hz cutoff sounds about right.
The good news is that three or four accelerometers will measure pitch and roll succesfully.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: angular accelerations through accelerometers
for my measurements, it is better to use the accelerometer in DC coupling or in AC coupling?
I haven't understood, what do you mean for " 0.3 Hz cutoff sounds about right". Which cutoff frequency do you means? Do you mean the accelerometer natural frequency?
RE: angular accelerations through accelerometers
Disregard most of my comments, since I made the incorrect assumption that you were measuring angular acceleration (torsional vibration) of a rotating shaft.
"for my measurements, it is better to use the accelerometer in DC coupling or in AC coupling?" You have to understand what the measurements are for; need static acceleration (0 Hz) or not.
Forget about the two low sensitivity accelerometers you have and get the appropriate sensor. Here are two expamples:
http://
http://www
My advise is to spend some time understanding what is needed (requirements and end use) for the measurements before making the measurements.
Walt
RE: angular accelerations through accelerometers
Thanks for the suggested sensors, but I believe we haven't these on my company, I will try to ask a collegue.
However probably I can find some accelerometers with +/-5g of full scale, do you think with those ones can I measure the vehicle pithing and rolling accelerations with a good accuracy? Moreover I don't need to know the centre of rotation, but only the distance between the two accelerometer, isn't it?
RE: angular accelerations through accelerometers
RE: angular accelerations through accelerometers
RE: angular accelerations through accelerometers
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: angular accelerations through accelerometers
ISO road vehicles standard reccomeds these instrumentation maximum errors and full scale:
max error full scale
lateral acceleration +/- 0,15m/s^2 +/- 15ms^2
roll rate +/- 0,2°/s +/-20°/s
for pitch rate I have found nothing.
So do you think whit +/-5g full scale accelerometer it is possible to perform good measures?
I have found the following sensor, it is cheap, do you think it is good enough?
http://ww
RE: angular accelerations through accelerometers
full scale maximun error
for angles: +/-15° +/-0.15°
for angles rate +/- 50°/s +/- 1°/s
so If I have two accelerometers with a maximum error of 0.25g and the distance between the accelerometers is 0.85m, so the maximum error of angle acceleration should be 0,21°/s^2. So how can I asses if the maximum error of my instrumentation is good enough? I hope I have explained better my need.
thanks
RE: angular accelerations through accelerometers
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: angular accelerations through accelerometers
RE: angular accelerations through accelerometers
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: angular accelerations through accelerometers
RE: angular accelerations through accelerometers
sqrt(2)*σ/sensor_spacing
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: angular accelerations through accelerometers
if the max error is 0,25g and the sensor spacing is 0,85 should the max error for angular acceleration be 0,25/(2*0.85)=0,14deg/s^2?
Whereas I'm interested to a frequency range 0-5Hz, is there a way to compare that angle acceleration error to the angle rate rate error of 1°/s? Only for understanding if the measure should be good enough.
RE: angular accelerations through accelerometers
- Steve
RE: angular accelerations through accelerometers
Then, you need to pay attention to the units. This is pretty sloppy work as an engineer.
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: angular accelerations through accelerometers
I have another question, if for example I need to measure the angle rate with the maximum error of +/-1°/s, but if I measure the angle acceleration what should its maximum error be for having the same max error in calculating the angle rate as integrate of the angle acceleration ?
RE: angular accelerations through accelerometers
TTFN
FAQ731-376: Eng-Tips.com Forum Policies