This article discusses the revolution that smartphones, apps, and add-on devices have brought in every person’s life. Sensors and apps are turning smartphones into engineering measurement tools. Increasingly, engineers are reaching for their smartphones to test products and equipment. The latest generation of smartphones feature sensor suites and apps that have turned the smartphone into a pocket-size laboratory of engineering instruments. Smartphones and apps have matured far beyond the consumer market to become real engineering tools. In 2013 Samsung Electronics Co. Ltd., added temperature and humidity sensors and pulled ahead of the market with the largest sensor suite. Many apps are available free to the user. The developers monetize their offerings by putting ads in the apps or by offering purchases to upgrade to a ‘pro’ version of the app with more functionality. The apps have also been used in industry to diagnose problems associated with vibration in mechanical systems, and by an electrical company that uses vibration to determine tension in cables. Smartphones, apps, and add-on devices are evolving rapidly, and a smart choice could make your next engineering project go mobile.
The latest prototype of the fan looked good. The air flow met the specification. There was just one problem—an annoying whine. What was causing it? The first step would be to use a frequency analyzer to pinpoint the frequency of the whine. However, we did not have a frequency analyzer, or the budget or time to get one.
My phone buzzed with an incoming text message, interrupting our work. It turned out to be a welcome interruption, because it drew my attention to my smartphone, and I remembered the frequency analyzer app that I had recently downloaded to try out.
I started up the fan again, and took frequency spectrum measurements with the app. There it was—a peak that corresponded to the whine. Just to be sure, I used another app, a frequency generator, to generate a tone at the peak frequency. The generated tone sounded just like the whine.
So the next step was to see if the whine was being generated by the blade passing frequency—the frequency at which the fan blades pass the closest point on the housing. A quick calculation using the number of blades on the fan and the motor rpm showed that the fan blade passing frequency matched the whine frequency. Mystery solved.
We could now consider changing the number of fan blades to shift the whine frequency into a range that cannot be heard as well by the human ear. That would quiet the whine to an acceptable level.
Increasingly, engineers are reaching for their smartphones to test products and equipment. The latest generation of smartphones feature sensor suites and apps that have turned the smartphone into a pocket-size laboratory of engineering instruments.
Smartphones and apps have matured far beyond the consumer market to become real engineering tools. The first generation of engineering apps focused on providing handbook information, CAD and drawing capability, and calculators for engineering formulas or unit conversion.
Now there are apps that can replace tachometers, hygrometers, seismographs, frequency analyzers, and other instruments to make serious engineering measurements immediately available, often at no cost and with no accessories. These apps have been enabled by the rapidly developing sensor suites available on smartphones.
Although smartphones had been around for several years, Apple Inc.’s introduction of the iPhone in 2007 began the era of smartphones with sensors. The first iPhone had a proximity sensor and an accelerometer. In the following years, smartphone manufacturers added sensors including magnetometers, digital compasses, gyroscopes, and barometers.
In 2013 Samsung Electronics Co. Ltd., added temperature and humidity sensors and pulled ahead of the market with the largest sensor suite. In 2014, Samsung maintained dominance in smartphone sensor suites with the Galaxy Note 4 phone, which has heart rate, oximeter, and UV sensors.
Samsung offers “a wide variety of sensors on our devices to allow users to capture accurate information with minimal to no human interaction,” the company said. “Sensors provide a great way to continuously provide critical data to allow smarter decision making across multiple industries.”
Many apps are available free to the user. The developers monetize their offerings by putting ads in the apps or by offering purchases to upgrade to a “pro” version of the app with more functionality. The free versions generally offer plenty of engineering functionality, such as calibration and data export, with minimally intrusive ads.
The Android app SpecScope Spectrum Analyzer by Nfx Development of Manchester, U.K., was used to measure the fan whine. The Frequency Sound Generator app by José Morais, a developer in Lisbon, Portugal, was used confirm the whine frequency by generating a peak-frequency tone to compare to the whine.
Zephyrus Wind Meter for Android from Gaia Consulting of Verona, Italy, uses the sound of air passing over the smartphone microphone to measure air speed up to 20 meters per second. It displays a wind speed versus time chart along with average and maximum values. Although originally designed for meteorological applications, it can successfully be used as an anemometer to measure velocity of air output by small fans.
A rudimentary night vision app can be used as an alternative to a flashlight in dim rooms. The Android app Night Vision Camera by Fingersoft Ltd. in Kempele, Finland, uses the smartphone's camera (so no infrared sensing), but it boosts visibility in low light by shifting images to the green color spectrum, to which the human eye is more sensitive.
Although most apps are published by individuals and small companies, some are now published by major tool supply companies. For example, the Ridgid Digital Bubble Level for both iPhone and Android comes from the Ridgid Tools Division of Emerson, in Elyria, Ohio. It can be used to level equipment conventionally with the smartphone placed on a surface, or remotely through use of the camera.
Humidity sensors are relatively new to smartphones. Only Samsung's Galaxy S4 and Note 3 phones have them at this time.
The Physics Toolbox by Vieyra Software of Washington, D.C., uses these humidity sensors in its hygrometer app, which is available as a stand-alone for iPhone or Android. It is also available as part of the larger Physics Toolbox Sensor Suite, which includes the hygrometer as well as a g-force meter, linear accelerometer, gyroscope, barometer, proximeter, thermometer, magnetometer, light meter, sound meter, tone generator, orientation meter, and a stroboscope.
According to Chrystian Vieyra of Vieyra Software, “The Physics Toolbox apps have been used by a doctor who studies head trauma, a test pilot from the military who was looking for cheaper ways to measure g-forces, researchers in the naval aircraft industry, researchers in directional drilling that use the magnetometer app to test for rogue magnetic fields in their equipment, and dancers who want to quantify their abilities using accelerometers. The apps have also been used in industry to diagnose problems associated with vibration in mechanical systems, and by an electrical company that uses vibration to determine tension in cables.”
Helen Lucke, a researcher at Covance Laboratories Ltd. in Harrogate, U.K., has used The Physics Toolbox accelerometer app to help train patients in the correct technique for handling a metered dose inhaler.
An MDI has a canister containing the drug and a propellant, and must be shaken by a patient to suspend the drug for delivery. The frequency and intensity of the shaking varies with personal technique and can influence the drug delivery.
To investigate the effects of various shaking methods, users in a study were asked to hold and shake an inhaler, then to hold and shake a smartphone in the same manner. The accelerometer in the smartphone and the accelerometer app in The Physics Toolbox provided a trace that characterized each approach to shaking the MDI. When compared to the drug delivery data for each shaking method, the preferred shaking mode became clear.
This resulted in a very detailed recommendation for shaking MDIs for best drug delivery: “Keeping your elbow still and holding the canister so the mouthpiece is pointing away from you, shake the canister in an arc for 5 seconds at 1 cycle per second (i.e. using a windscreen wiper-like motion).”
Concerns about air pollution are driving some of the newest available sensors for smartphones. Robert Bosch GmbH of Stuttgart, Germany, is a major sensor supplier to smartphone manufacturers. The company offers a sensor suite that combines a gas sensor with pressure, temperature, and humidity sensors, and provides volatile organic compound detection in the parts per million range. VOCs are outgassed from paint, adhesives, pesticides, furniture, and building supplies, and these pollutants tend to build up indoors leading to air quality concerns.
CO2 concentration is another measurement of air quality. Asahi Kasei Microdevices Corp. of Tokyo, Japan, manufactures infrared photo-diodes that can be used to detect CO2 spectroscopically.
Already there are a range of add-on devices to extend the functionality of smartphones with many different types of sensors. These range from low cost, maker-style options to more expensive professional grade devices.
The American Physical Society of College Park, Md., offers SpectraSnapp, an iPhone app that works with a simple accessory to turn the phone into a spectroscope for the identification of light emitting materials. For those with access to a simple maker-space or home workbench, directions are available at itunes.apple.com for making a simple spectroscope that fits over the smartphone camera.
For phones without humidity and temperature sensors, a German company, TFA Dostmann GmbH & Co., offers the Smarthy thermo-hygrometer which plugs into the headphone port on Apple and Android mobile devices. At about $45, it is in the middle price range of smartphone peripherals. It is available in the U.S. through Amazon.com from Dostmann's distributor, LaCrosse Technology of La Crosse, Wis.
Beyond rudimentary night vision apps that shift the color spectrum, FLIR Systems Inc. in Wilson-ville, Ore., offers true thermal imaging as an addon to either iPhone or Android. Seek Thermal Inc. of Santa Barbara, Calif., also offers true thermal imaging accessories for both iPhone and Android. In the $200 - $300 price range, these are among the more expensive peripherals available.
In 2013, the Kickstarter-funded company, Sensorcon of Buffalo, N.Y., launched the Sensordrone with 11 sensors that communicate with a smartphone via Bluetooth. According to Sensorcon, the device measures “carbon monoxide levels, hydrogen sulfide levels, ambient temperature, humidity and pressure, non-contact infrared temperature, oxidizing and reducing gases, and more.” Now the company is working on a new product, Sensor-drone Core, which can be tailored with a smaller sensor suite to application-specific needs.
Even well-established companies are working on integrating their conventional instruments with smartphones.
Fluke Corp. of Everett, Wash., offers Fluke Connect to connect its conventional instruments with smartphones to identify, diagnose, and share data.
The next time you consider upgrading to a new smartphone, consider the sensor suite, and the apps and accessories that are available for your phone of choice. Smartphones, apps, and add-on devices are evolving rapidly, and a smart choice could make your next engineering project go mobile.