## Acceleration (without g)

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The experiment “Acceleration (without g)” just gives the raw data from the phone’s (typically virtual) accelerometer.

Note, that there is a possibly confusing distinction between “Acceleration with g” and “Acceleration (without g)”. The sensor in your phone actually measures a force on a sample mass, which includes the contribution from gravitational acceleration. Therefore, this sensor will report the earth’s acceleration of 9.81 m/s² while the phone is resting (which is what we call “Acceleration with g”). In contrast, the physical acceleration is zero when the phone is resting (or moving at a constant speed), so most phones offer a virtual sensor which subtracts the constant acceleration (usually by taking into account the data from other sensors as well). This is what we call “Acceleration (without g)” and it will actually report an acceleration of zero while the phone is not accelerated.

## 4 thoughts on “Acceleration (without g)”

1. Jeremy Béguelin says:

Is that possible to increase the sampling?

1. Sebastian Kuhlen says:

If you have an up to date version of phyphox (1.0.6, released on 24 February 2017), the rate should already be the maximum supported by your device. For older versions there was a limit of 25Hz for the raw experiments, but custom experiments could be as fast as possible (that is, again, as fast as supported by the device).

In general, you can create a simple custom experiment by pressing the “+” button on the main screen and set the desired rate for your sensor. Here “0” means as fast as possible and any other value means, that phyphox will average the data to get close to your desired rate (again, it can of course not exceed the hardware limits).

1. Eric Byrne says:

Could I use this channel to collect road noise and compare it to a channel that tracks gps location. For example, If I wanted to check how bumpy the route was between a hen house and the egg distributor ?

1. Sebastian Staacks says:

Sorry for the late reply.

In principle, this should be possible, although in practice there might be a few things to consider:
– When trying to measure bumps in a road, you need to mount the phone in a way that it does not pick up too much vibration. If the phone is simply fixed to a truck, the vibration from the motor can be much stronger than the bumps you are interested and you will see more noise than the actual bumpyness of the road. This will depend on where you mount the phone and some damping might help as well… Or maybe the most realistic thing would be to place the phone between the eggs 🙂
– You can easily record acceleration and GPS simultaneously in phyphox, but it might be difficult to plot it in a way that is easily interpreted. To plot the vibration directly against the GPS coordinates, you either need to only record acceleration on each GPS fix (which would be much slower than what you need) or duplicate the GPS data to assign them to each acceleration reading (which should work fine if you don’t mind the redundant data). Both can be set up with our editor (see menu at the top), but still, plotting the acceleration against longitude and latitude is not really the most intuitive way to view it. I would rather suggest, to create a simple experiment (using the “+” button in the main menu) and check acceleration and location to record both over time. Simply export the recorded data somewhere else (for example Excel) and simply look up the times of relevant features, look up the coordinates at that time in the GPS data and enter it in Google Maps to see the location at which this feature occurred.