Understanding Shock Sensor G-Force Ranges & Outputs

In summary: If you are looking for a sensor with a certain range, you would need to find a sensor that has that range. Piezo crystal sensors generally have a range of 10,000g-20,000g. A sensor that has a higher range would be better because it would be able to measure smaller shocks. The maximum acceptable acceleration for a piezoelectric sensor is 50,000g. If you are looking to measure shocks that are above this range, you would need to use a different sensor.
  • #1
samodelov.1
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I have no experience with shock sensors and am looking for some insight. The ones I have found say a range in g's (example - range: 10,000g) and then give a maximum value. I was wondering if the range would be similar to a minimum that the sensor is able to read or how close to the given range I would have to be in order for it to give me an output. Supposedly, it is not going to give any output if there is just some weight on the sensor (if I understand correctly), but can it be damaged if a weight (well below the maximum) is placed on it for a sustained amount of time? Thanks!
 
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  • #2
I'd doubt that you can damage it by putting on a small (but reasonable) load on top of the IC, because, well, you're probably not actually causing the sensing element to actually do anything (more than likely, you're just applying this load to the device package). I'm not a devices expert, however, the designs that I've seen have micro paddles inside of a cavity that deflect whenever the device is accelerated. However, something like a strain gauge or force meter (where a load is applied and then measured) is a different beast altogether.

So, if you use this chip to prop up, say, a 5-ton hydraulic press, you'll probably smash the sensor. If you're attempting to load the sensor using, say, a sledgehammer, you'll also probably smash it, and do so before you can get anything out of the sensor. If you're just squeezing the device into your enclosure, you're probably okay.
 
  • #3
Chances are if it's a shock sensor it's probably a piezo crystal sensor, such as this. Piezoelectric sensors generally exhibit significant signal decay at frequencies comparable to the reciprocal of their time constant, meaning that a (quasi)statically applied loading may show a brief load but will tail off to zero. As a result, any static loads applied to the sensor shouldn't give a reading, but may affect the sensor's frequency response.

If you multiply the sensitivity (e.g. in my example above, 0.5 mV/g) by the acceptable range of accelerations (e.g. [itex]\pm[/itex] 10 000 g), you'll see the range of voltages the sensor can produce, in this case [itex]\pm[/itex]5 V. Accelerations above this will cause the sensor to read full output (e.g. 20 000 g will actually be output as 10 000 g or +5 V due to saturation).

The maximum tolerable acceleration or shock (here 50 000 g) is the maximum overload acceleration the manufacture has confidence in that the sensor can handle for a very short duration before damage is sustained.

So if you have a test setup where shocks of up to 7 000 g will be measured frequently but occasionally due to operator error can produce a single shock of up 20 000 g, you should be fine - a shock outside the maximum measureable range will be clipped.

Have a read through the information on the PCB website for more information regarding sensors in general, especially piezo ones.
 
  • #4
Thanks for all the information! It has been really useful, especially the PCB website. I would be using the sensor more as a switch to trigger the next action and just need the step response, rather than an exact and repeatable voltage.

I want to make sure that I get a sensor with the correct range to give me a response but last as long as possible. I assume that there would be a decay over time of the response. Do you know how I can calculate the life of a piezoelectric sensor? If anyone knows on average how many cycles a piezoelectric sensor can still give a decent step response, that would also be helpful. It would be best though if I could calculate how low I would need to put the threshold voltage for the next action, figuring in decay over time. I'd like to use it for a couple years, if possible, with only a couple cycles a day.

Thanks!
 

1. What is a shock sensor?

A shock sensor is a device that detects sudden, rapid movements or impacts and converts them into an electrical signal. This signal can then be used to trigger an alarm or activate a safety mechanism.

2. How does a shock sensor measure G-forces?

A shock sensor typically contains a mass suspended by a spring. When a sudden movement occurs, the mass will move and compress the spring, producing a force proportional to the G-forces experienced. This force is then converted into an electrical signal for measurement.

3. What is the range of G-forces that shock sensors can measure?

The G-force range that a shock sensor can measure varies depending on the specific sensor. Some sensors may have a range of 10G, while others can measure up to 100G or more. It is important to choose a sensor with a range appropriate for the application it will be used in.

4. What are the outputs of a shock sensor?

The output of a shock sensor is typically an electrical signal, such as voltage or current, that can be measured and recorded. Some sensors may also have a visual or audible alarm output in addition to the electrical signal.

5. How can understanding shock sensor G-force ranges improve safety?

By understanding the G-force range that a shock sensor can measure, safety measures can be implemented to protect against potentially dangerous impacts or movements. For example, in a vehicle, a shock sensor can trigger the deployment of airbags if a certain G-force threshold is exceeded, protecting the passengers from injury.

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