About this app

"Working Scale" uses your phone's sensors to measure the mass of a small object placed on it. The minimum mass you can measure accurately with typical Android devices is about 5 grams. Best results can be obtained for masses between about 10 and 100 grams.

For example, if you place your Android device on a carpet and gently push down on one end with your finger, it will come back to its original position after you remove your finger. The carpet has spring-like properties.

This app is designed to make use of the spring-like properties of common objects in combination with a known mass (a "calibration mass") to measure an unknown mass. Two different methods are employed by "Working scale". The first method measures the tilt angle of the Android device when an object is placed on it. The second one measures the oscillation period of the Android device when an object is placed on it and they are set in motion when resting on a springy object (a meter stick or yard stick). The app tracks your device's changing angle using its built-in motion sensors.

Here are the steps you should follow to get the best results:

Tilting method:

1. Place your Android device face-up on a carpet, sofa cushion, slightly inflated Zip-lock bag (good), flexible "ice pack(s)" (best), folded towel, or any other "springy" object. It helps to place a small piece of paper on your Android device where you plan to place the calibration mass. This makes it less likely that it will slide.

2. Press the 'Start' button. Do not touch the device again until it commands you to place the calibration mass on it.

3. For users in the USA, we recommend using at least one quarter for the calibration step (but two quarters is better). You should use more coins for larger devices. You should easily notice movement of the device when you place the coin(s) on it. You can look up the mass of a quarter (or other coin) on the US mint coin specifications web page (http://www.usmint.gov/about_the_mint/?action=coin_specifications). Watch the progress bar and make sure you place the coin(s) on the device after the progress bar begins moving, and make sure the device stops moving before the progress bar reaches the end. You can enter the mass of the calibration mass in the 'Settings' page prior to starting your calibration and measurements. There, you can also enter the number of calibrating masses (for instance, one, two or three coins). As a general rule, the mass of your unknown object should not be too different from the total mass of your calibrating masses.

4. After the calibration step, place your unknown on top of the calibration mass. The accuracy is at best 0.1 gram; more often a single measurement will have an accuracy of 0.2 - 0.3 grams, but it will depend on the setup. You can run your own tests of the accuracy by placing known masses on the device.

5. When you are done, press the Stop button. Press the 'clear' button to reset the displays to '0.00'.

6. It is recommended that you enable the averaging display. It displays the average of every 10 measurements.

Oscillating method:

1. Place a meter stick or yard stick on a table, with about one-third of it off the end of the table. Place something heavy on the part of the ruler on the table (such as several large books).

2. Place the Android device near the end of the stick that is off the end of the table.

3. Press the 'Start' button, and follow the on-screen instructions.

A save button allows you to store measurements.

Be careful when trying to measure liquids that you do not spill any on your Android device.

If you have any suggestions for improvements or just want to share with us your interesting project with this app, please contact us at ggonzo47@gmail.com

Use "Working Scale" for science experiments, measuring small quantities of ingredients for a recipe, or making a game of guessing masses or weights.

The accuracy is about +/- 0.2 grams. This is NOT a gag app!

"Working Scale" doesn't have any ads.

New features

Version 1.5: fixed problem with back button. Fixed several more UI issues.
Version 1.6: added option to keep screen on or not. Additional UI adjustments.
Version 2.0: major update. Improved the stability of the readings.
Version 3.0: Another major update. Added a completely different second method for measuring mass.
Version 3.1: UI adjustments.
Version 3.2: Updated to work on newer devices.