How Good is Your Mobile Phone as an Angle Gauge?

I wanted to know how good is your Mobile Phone as an Angle Gauge? So I checked it against a known set of angles and a known gauge.

Using a surface table and a sine bar

So I set up an experiment using a surface table (an accurate flat plate), a sine bar and a Wixey angle gauge. This allows me to set an an accurate angle with the sine bar and then compare this to a digital gauge and a phone.

The phone in question is a Samsung A71 running Android.

A sine bar is essentially a triangle where the bar itself is a 5 inch long hypotenuse and the slip gauges are precise thicknesses and form the opposite side. Hence sine(angle) = opposite length / hypotenuse length.

First was the turn of the Wixey digital angle gauge. This does have a benefit of a magnetic base. Firstly I place the sine bar on the flat surface plate and set the angle gauge to zero. Then set about changing the angle of the bar with the different heights I could achieve with a combination of slip gauges. I recorded all of the values.

Wixey Digital Angle Gauge

Then I started the angle gauge on the phone. You can do this on the latest Android phones by carefully pulling the tab across from the right hand side of the main window. You will see a slither of grey 2/3rds of the way up the screen. Pull this tab out and you will get options such as: Compass, Tally counter, Torch, Surface level, Ruler. There is also a settings icon that allows you to change the options available.

Select the Surface level and turn your phone on it’s side. You now have an Android angle gauge. So, how good is your mobile phone as an angle gauge?

phone used as an angle gauge
Image shows angle is 17.5°

I calibrated the phone once I had placed it on edge on the sine bar and with the sine bar flat on the surface table. I then repeated the steps of increasing the height (length of the opposite edge). Again I recorded all of the values.

I entered all of the values recorded into a spreadsheet, converted the sine gauge values to angles and plotted these versus the gauge measurements.

actual versus measured angles
Measured versus Actual Angles. The grey line is the perfect absolute line.

From the plot you can see that both devices give very accurate values. Interestingly the Samsung A71 gives more accurate values above 30°. I calculated the RMS errors for both devices and the Wixey digital angle gauge is +/-0.22° and the Samsung A71 is +/-0.12°.

What this does say to me is that you can trust both devices. Also, the only advantage of the Wixey gauge is it is compact and has a magnetic base. Otherwise, you could replace the Wixey angle gauge with your phone.

Since posting this article someone asked me to plot the error in each device versus the absolute angle. This is an interesting plot as you can see the error increasing as the angle increases.

mobile phone angle error

2 thoughts on “How Good is Your Mobile Phone as an Angle Gauge?”

  1. That is amazing, it just goes to show how sophisticated software can manage a simple sensor very well indeed. Rhanks for posting.

    • Hi Roger, yes, it is rather good. It’s even worth making a simple holder for the phone. I haven’t tried other phones yet though. Best regards, Nigel


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