Q: Why does PocketMeter not run on my first generation iPhone?
A: The microphone on the first generation iPhone is not sensitive enough. For a more technical explanation: The first generation iPhone can only record at a sample rate of 8kHz (compared to 44.1kHz on the new iPhone 3G) on its internal microphone, which is not sufficient for our distance measuring algorithms.
Q: Why does PocketMeter not run on my iPod touch?
A: PocketMeter requires a built-in microphone and speaker to operate.
Q: How does PocketMeter work?
A: PocketMeter emits sound and measures the time it takes for the echo to return. Using this information and the law of physics (speed of sound) the distance can be calculated. We have developed sophisticated algorithms to improve the accuracy and filter the results to make PocketMeter suitable for most environments.
Q: What can I measure?
A: As PocketMeter relies on an echo to measure, it can measure distances to objects that reflect sound. Good examples are flat walls and floors. If the target consists of soft material, like carpet or curtain, no echo will be reflected and it will be difficult to calculate the correct distance. If you want to measure an object (e.g. table, bed), try placing it next to a wall and use the wall as the target.
Q: Why can measuring be tricky at times?
A: PocketMeter measures the echo – but because the speaker on the iPhone emits sound in multiple directions, there may be unwanted echoes. Let us assume you want to measure the distance to a wall, but the echo also gets reflected on your table, chair and even your body. Our algorithms try to evaluate which echo may be the intended one, but in certain circumstances might fail to do so. If you believe the result is incorrect, try tilting or twisting the iPhone slightly, so the sound takes a slightly different route.
Q: Why do I need to enter a temperature and how accurately must it be?
A: Sound propagation is dependent on air temperature. In hot air, sound travels faster than in cold air. Luckily the effect of temperature does not have a very big impact. Usually it is sufficient to estimate the temperature within a range of 5 °C (10 °F) to achieve an accuracy of 1% - e.g. if you enter 25 °C (77 °F), but the actual temperature is 20 °C (68 °F), PocketMeter will show 99 cm (99 inches) instead of the correct 1 m (100 inches).
Q: What is the operating range?
A: PocketMeter can measure distances from approximately 20 cm (8 inches) to 4 m (13 ft) - the minimum distance slightly depends on your iPhone hardware, so on some iPhones the minimum distance is slightly higher.
Q: My iPhone always shows a constant distance reading (e.g. 0.31 m), what should I do?
A: Update PocketMeter to the newest version - the very first version released on the AppStore had a problem, where some users always got a constant distance reading. After investigating the issue, we found out, there are some slight differences in the iPhone hardware (most probably due to manufacturing variations), which caused this problem.
The microphone and speaker on the bottom of the phone should not be covered by any obstacles, usual suspects are:
- iPhone covers: Please make sure the holes for the microphone and speaker are not covered.
- Dirt and dust: If you put your iPhone in your pocket, dirt and dust might cover the microphone and speaker holes. Gently blow off the dust.
Q: What is this "Min. Distance" all about?
A: When PocketMeter emits sound, this sound also produces vibrations on the iPhone case, microphone and the speaker itself. This will introduce interference with our echo measuring algorithms, because those vibrations produce false echoes, especially on the lower range (less than 50 cm, 20 inches). Because there are normal iPhone manufacturing differences, those interferences can be different from iPhone to iPhone. On the original release the minimum distance was set to 20 cm (8 inches), which was a bit to optimistic. On the new release, the minimum distance can now be set by the user and defaults to 50 cm (20 inches) which should work for most iPhones. If you still see a constant reading, try to further increase the value or if you never experienced any problems so far, you can also try to lower the value again.
Q: What is the accuracy I can achieve?
A: The theoretical limit is around 1 cm (0.4 inches), if you entered the correct ambient air temperature.
Q: The temperature will stick to 0°, even when I try to adjust it. Is this a bug?
A: If you downloaded a pirated version of PocketMeter, the temperature can't be adjusted and will stay at 0° all the time. If you like the application, consider buying a legitimate copy from the AppStore.
Q: I would like to use PocketMeter to decide if my new truck will fit into my garage, what do you recommend?
A: Do not use PocketMeter for critical measurements. We are not responsible for any inaccuracy and the result of your action.