The sensor will be fixed onto the wall of the building.
It's not only cars so it could be multiple elements effecting the structure but would like to get a better understanding of vibration that could be affecting the structure..

OK with that in mind I suggest you read this paper by Bruel and Kjaer and then this Endevco paper attached PDF. That should get you started on measuring shock and vibration. I have used products from both extensively over the years. Next when collecting data, any data, you need someplace to put it. You also need to consider environment of where sensors are placed and axis of concern.

Here is a crude example of affixing an accelerometer to a floor fan.


The output goes to a charge amplifier and then is recorded and charted.


The accelerometers look like this.



These are typical accelerometers used in industrial environments. You won't find them on Ebay or in a cheap parts bin. They are calibrated. You need to decide what is suitable for your specific application.

Ron

 

You can do a DIY seismometer. When I first built my version, I installed it on the basement floor of a townhouse in a city. It was essentially useless for sensing low-level seismic activity because it had too much interference - it could sense someone walking in the townhouse, walking on the sidewalk in front of my townhouse and could definitely sense each passing vehicle.

 

The question which hasn't been answered is what is the goal of the measurements. Is it to detect motion? Is it to determine of level of vibration? If it is to measure vibration, what resolution is needed?

Acceleration is a crap way of measuring displacement at low frequency. Is displacement a necessary part of the goal? Acceleration will be more sensitive (at least if an accelerometer is used for the measurement).

Displacement sensors won't work without a convenient skyhook to provide a fixed reference point.

Maybe strain gages? Depends on what the goal is and if there's a place to measure strain.

So the question remains – what is the goal?

 

The question which hasn't been answered is what is the goal of the measurements. Is it to detect motion? Is it to determine of level of vibration? If it is to measure vibration, what resolution is needed?

Acceleration is a crap way of measuring displacement at low frequency. Is displacement a necessary part of the goal? Acceleration will be more sensitive (at least if an accelerometer is used for the measurement).

Displacement sensors won't work without a convenient skyhook to provide a fixed reference point.

Maybe strain gages? Depends on what the goal is and if there's a place to measure strain.

So the question remains – what is the goal?

They only remain unanswered when you don't read the answers.

The sensor will be fixed onto the wall of the building.
It's not only cars so it could be multiple elements effecting the structurebut would like to get a better understanding of vibration that could be affecting the structure..

 

You can do a DIY seismometer. When I first built my version, I installed it on the basement floor of a townhouse in a city. It was essentially useless for sensing low-level seismic activity because it had too much interference - it could sense someone walking in the townhouse, walking on the sidewalk in front of my townhouse and could definitely sense each passing vehicle.

Thanks, this could work for my application. How do I start with a seismometer?

 

The question which hasn't been answered is what is the goal of the measurements. Is it to detect motion? Is it to determine of level of vibration? If it is to measure vibration, what resolution is needed?

Acceleration is a crap way of measuring displacement at low frequency. Is displacement a necessary part of the goal? Acceleration will be more sensitive (at least if an accelerometer is used for the measurement).

Displacement sensors won't work without a convenient skyhook to provide a fixed reference point.

Maybe strain gages? Depends on what the goal is and if there's a place to measure strain.

So the question remains – what is the goal?

The goal is to detect movement in a structure, which initially will be a house.
Yes, it will be based on detecting vibration. Motion might not be necessary.

Well what is the realistic resolution that is needed? I would have thought a small moment of 1mm would be execpeted. Unless i am wrong.

Displacement is not necessary, just vibrations or minium movement.

 

Thanks, this could work for my application. How do I start with a seismometer?

https://www.instructables.com/DIY-Seismometer/

That is a start - you can also go crazy with Log amplifiers tuned to multiple ranges and raspberry pi's with remote data storage. Add two more seismometers to triangulate the source of the activity and velocity of the propagated wave.

 

OK with that in mind I suggest you read this paper by Bruel and Kjaer and then this Endevco paper attached PDF. That should get you started on measuring shock and vibration. I have used products from both extensively over the years. Next when collecting data, any data, you need someplace to put it. You also need to consider environment of where sensors are placed and axis of concern.

Here is a crude example of affixing an accelerometer to a floor fan.
View attachment 266261

The output goes to a charge amplifier and then is recorded and charted.
View attachment 266262

The accelerometers look like this.

View attachment 266263

These are typical accelerometers used in industrial environments. You won't find them on Ebay or in a cheap parts bin. They are calibrated. You need to decide what is suitable for your specific application.

Ron

Hi, What is the pricing for such accelerometers? Are they outputting a analogue signal?

 

Hi, What is the pricing for such accelerometers? Are they outputting a analogue signal?

There are all types and qualities. You can get analog output but these are limited in functionality because you need to find one that matches the range you want to look at. Otherwise, many of the significant digits are kind of useless if your signal doesn't really fill the dynamic range of the sensor.
Better is to get a sensor with a much bigger range and many more bits of resolution then you think you need. That way, your uncharacterized movement can be captured.
Search accelerometers on Digikey.com and use the parametric search to narrow down to find what you want / need.

 

You can also download an app to your phone and use the accelerometer on your phone. Fasten your phone to the vibrating structure. Watch the numbers.

 

Hi, What is the pricing for such accelerometers? Are they outputting a analogue signal?

They are expensive to very expensive. Last ones I bought were over $1000 USD each. If all you want is something to sense vibration at a hobby level and do not need any degree of accuracy then I would take the route suggested by MrSalts Post #22. If you just want to measure vibration in a wall and don't care about the accuracy then an inexpensive sensor will do just fine. The PDF I posted from Endevco explains things as to vibe and shock sensing. A Google of vibration sensing will get you a dozen hits. You need to decide what works best for your application including environment. Also if you want to log the data you get.

Ron

 

The goal is to detect movement in a structure, which initially will be a house.
Yes, it will be based on detecting vibration. Motion might not be necessary.

Well what is the realistic resolution that is needed? I would have thought a small moment of 1mm would be execpeted. Unless i am wrong.

Displacement is not necessary, just vibrations or minium movement.

MrSalts has all the answers, so I will defer to his vast knowledge. I've only been involved in vibration analysis for 40 years with a patent in the field.

You might study a bit on the relationship between acceleration, velocity and displacement and spend some time understanding what results you are looking for, but again, this is only based on 40 years of doing all types of vibration analysis.

 

MrSalts has all the answers, so I will defer to his vast knowledge. I've only been involved in vibration analysis for 40 years with a patent in the field.

You might study a bit on the relationship between acceleration, velocity and displacement and spend some time understanding what results you are looking for, but again, this is only based on 40 years of doing all types of vibration analysis.

I don't have all the answers, I just read the OP's posts and give the answers I have. If you have something to add, add it. If you think I'm wrong, say it. Just don't accuse me of having all the answers.

 

If you just want quick and simple spend a few dollars (USD) on Amazon and get a few of these. Glue one to the end of an old hacksaw blade and see if that works out for you. Less knowing a budget and how accurate you want this I can't add anything.

Ron

 

Or you can get 15 sensors for about the same price.

https://www.amazon.com/TIMESETL-Pickup-Amplifiers-Acoustic-Guitar/dp/B077YJ3H6R/ref=sr_1_4

 

Or you can use an digital IMU with a decent MEMS accelerometer:
BMX160 https://www.bosch-sensortec.com/media/boschsensortec/downloads/datasheets/bst-bmx160-ds0001.pdf
https://forum.allaboutcircuits.com/...2210-on-linux-with-libusb.179080/post-1691231
180 μg/√Hz

• 3-axis, ±2.0 g full-scale
• 16-bit data output

Or a low noise accelerometer like this:
LIS3DHH https://www.st.com/en/mems-and-sensors/lis3dhh.html
45 μg/√Hz

• 3-axis, ±2.5 g full-scale
• 16-bit data output

These are nice but a really good unit for what the OP wants (microtremor seismometer measurements) will cost a bit with a analog front-end to match.
https://www.jae.com/files/user/motion-sense-control/catalog/ja-40ga-en.pdf
0.1 x 10-6 G/√Hz max.

Dangerous special gases and chemicals are handled at semiconductor manufacturing plants. Earthquake detection and mitigation systems are common additions to other safety systems.

 

Or you can use an digital IMU with a decent MEMS accelerometer:
BMX160 https://www.bosch-sensortec.com/media/boschsensortec/downloads/datasheets/bst-bmx160-ds0001.pdf
https://forum.allaboutcircuits.com/...2210-on-linux-with-libusb.179080/post-1691231
180 μg/√Hz

• 3-axis, ±2.0 g full-scale
• 16-bit data output

Or a low noise accelerometer like this:
LIS3DHH https://www.st.com/en/mems-and-sensors/lis3dhh.html
45 μg/√Hz

• 3-axis, ±2.5 g full-scale
• 16-bit data output

These are nice but a really good unit for what the OP wants (microtremor seismometer measurements) will cost a bit with a analog front-end to match.
https://www.jae.com/files/user/motion-sense-control/catalog/ja-40ga-en.pdf
0.1 x 10-6 G/√Hz max.

Dangerous special gases and chemicals are handled at semiconductor manufacturing plants. Earthquake detection and mitigation systems are common additions to other safety systems.

This is very interesting. The BMX160 and ST solution being 16-bit, does that mean each bit could be representing a less than cm> of movement?

 

MrSalts has all the answers, so I will defer to his vast knowledge. I've only been involved in vibration analysis for 40 years with a patent in the field.

You might study a bit on the relationship between acceleration, velocity and displacement and spend some time understanding what results you are looking for, but again, this is only based on 40 years of doing all types of vibration analysis.

Where would be starting point to under the all these topics. I presume YouTube could be good choice?

 

This is very interesting. The BMX160 and ST solution being 16-bit, does that mean each bit could be representing a less than cm> of movement?

It's 16384 LSB/g sensitivity of a noisy signal. There are ways to reduce the noise using DSP but they all have trade-offs in latency and bandwidth. You can add two, three or more accelerometer output samples at a time and divide by number of samples in the block to get the average each set of sample blocks with a low-pass filter. You can process this signal forever but it won't provide the actual sensitivity provided by an expensive microtremor seismometer sensor you need.
https://gi.copernicus.org/preprints/gi-2020-11/gi-2020-11-manuscript-version5.pdf

Here I'm collecting the raw BMX160 IMU x,y,z accelerometer data on a Linux system via USB and scaling it to normalized units for graphic display on a Java program with the quaternion w being magnetometer z data.

    /* Write to the pipe */
            snprintf(fifo_buf, 255, "%7.3f,%7.3f,%7.3f,%7.3f,%7.3f,%7.3f,%7.3f,%7.3f,%7.3f\n", magn.x, magn.y, magn.z, gyro.x, gyro.y, gyro.z, accel.x, accel.y, accel.z);

                System.out.println(String.format("w = %+7.3f     x = %+7.3f     y = %+7.3f     z = %+7.3f", w, x, y, z));
                Quat4d quaternion = new Quat4d((w * 0.05), x, y, z);
                Vector3d vector = new Vector3d((ax * 0.02), (ay * 0.02), (az * 0.02));
                transformGroup.setTransform(new Transform3D(quaternion, vector, 1.0));

This will give you a nice hand-waving display or a earthquake sensor but it won't detect cars next to a building.

 

So that I understand it correctly.

16-bit is 65535, so what is 16384?Maybe I misunderstood something?