October 5, 2020

Smart Meter Pro (v2.0) manual

Hello. I'm android boy, the chief developer of Smart Tools co,.

Smart Meter Pro is the NEW 4th set of the Smart Tools suite released in 2020. It includes 3 tools (sound meter, vibration meter, lux meter), and it is an improved app of "Sound Meter Pro". I will revise the content of this blog soon.

※ Introduction video

Ⅰ. Sound Meter
This tool is using your microphone to measure noise volume in decibels(db), and shows a reference.

① Menu
② Statistic menu (save / load / CSV export)
③ Screen capture
3 Red lines mean max, mean and min values.

④ Refresh : to reset, long-click on the center of meter or click this refresh icon

⑤ Text / Chart toggle

⑥ Black / White toggle : make your screen dim for saving battery
⑦ Play / Pause toggle

 Don't blame this app for Maximum Limitation

Most microphones are aligned to human voice (300-3400Hz, 40-60dB). It is enough for voice calls. But it occurs an issue of 16 bits microphone limitation.

See sound pressure at calibrate menu. It'll stop at 32767 (32767=2^15-1). In conclusion, 16 bits microphones cannot measure above 96 dB. (more link)

Because of additional optimization (background noise reduction), some devices can measure at most 80 dB. Galaxy S3-S5(81-84db), Galaxy Note(81/91db). Most of Motorola and Amazon devices can measure 96 dB fully.

Last year, a German user suggested a trick in order to bypass hardware limitation. Add +30dB at calibrate menu, and close your microphone hole with your finger, so that you can measure a sound over 100dB. Try it out. :)

 Menu & Settings

① Upside down : Most smartphones have a microphone hole at the bottom. It is recommended to point the microphone to the sound source. How? Upside down!

 Statistic Menu
① Save : enter title name for current chart
② Load : load the charts stored. To remove a chart, long-click and select [delete] option.

③ Export : export current data as CSV file into SD card. Move it into PC and open with MS-Excel. This function can store up to 48 hours. Here is an example.

 How to calibrate Sound Meter ???
Since 2010, we had calibrated the app on 500+ android devices (major Galaxy, LG, Xperia, Motorola and Nexus). It's a pity that the results were changed easily depending on OS version.

In order to calibrate the app correctly, you must compare it with an ACTUAL sound level meter. Otherwise, ensure that the measured value of a very quiet room is 30-35dB. If the result were out of range, you could add/reduce number at the calibrate menu.

It is an auxiliary tool for reference. Just enjoy it.

 Level Notification
A lot of users, especially school teachers, wanted to know if their voices were loud. Turn on [Level Notification] option at the settings.
60dB+ : green, 70dB+ : pink,  80dB+ : red. It is a pity that Sound alarm cannot be used due to amplification.

Ⅱ. Vibration Meter
This tool is using a 3-axis acceleration sensor so as to measure device's vibration, movement or the earthquake, and shows a reference. The value is related to Modified Mercalli Intensity scale(MMI). It has no unit.
① Menu
② Statistic menu (save / load / CSV export)
③ Screen capture

④ Refresh : to reset, long-click on the center of meter
⑤ Play / Pause toggle
⑥ Alarm : show current alarm situation

 How to calibrate Vibration meter ???
Most acceleration sensors are unstable and weakened easily, so that calibration is required.

① Go calibrate menu.

② Shake your device as possible as you can. Increase / decrease its sensitivity so that max value reaches about 10-11.
③ Check your unnecessary value measured by no movement.
④ Click [Cut Baseline] button and select an number.

⑤ Repeat ②-④ several times.

. Lux Meter
Light meter measures the ambient brightness with embedded light sensor. It is used to adjust the lighting required for plants or to check the brightness of a study room.

※ Main screen
This app shows the original/calibrated value, maximum, average and minimum.
① Refresh : Refresh the chart
② Chart Y-range : Select the vertical range of the chart (0-100, 250, 500, 1000, 5000) 
③ Play / Pause toggle

※ Point at the light source
For accurate measurement, make sure that your screen with the sensor is facing the ambient light source like the sun, sky, window, lamp and candle. An actual light meter has a large convex sensor, so it has a wide range of exposures. Meanwhile, the embedded sensor on smart device has a narrow range.

※ How to calibrate?
Go menu > calibration. Select factor option, and enter your own calibration value (range : 40 - 400%).
For example, measured value (200 lx), expected or actual value (300 lx) : enter 150%. 

X. etc
Q. It says "Unable to open microphone.".
A. Other app occupied your microphone. Just restart your device.

Q. Where can I find the Screenshot and CSV file?
A.  /storage/emulated/0/smart-tools/, /storage/sdcard0/smart-tools/, /mnt/sdcard/smart-tools/.

Q. I hear nothing. But the app shows 30-40 dB.
A. A microphone cannot catch very low-frequency noise. 0 dB means the vacuum of space.

Q. Is the result dBA weighted?
A. Yes, I calibrated the app with a actual SPL meter with dBA. But db(A) makes no sense because the result is not perfect.

Q. How to disable tick sound switching from chart to text?
A. Turn off [Sound effect] option at the settings.

Q. What is the unit of vibration?
A. It has no unit, just the scale for reference.

 What's new
 - v2.0.3 : Support for OS 11
 - v2.0 : Smart Meter Pro released (Oct. 2020)
If you have any idea to improve it, feel free to contact me at androidboy1@gmail.com. Thank you.