List of applications that DAQ systems can be used for
There are countless applications for data acquisition. Any physical phenomenon or physical property as a function of time is a candidate for data acquisition. Data acquisition is beneficial in both laboratory and industrial settings. However, with the advent of Internet of Things, data acquisition is now commonplace in the home, small business, or hobbyist garage. Educational applications range from middle school, afterschool programs, science camps, to high schools and universities. Engineering students, professors, and graduate researchers alike use DAQ systems everyday.
Below are some real-world examples of data acquisition applications.
Measuring the temperature of a chemical reaction with respect to time can be very insightful. At a very basic level, it can be indicative of whether the the chemical reaction is endothermic or exothermic. If the reaction is endothermic, the reaction is absorbing energy, thus the temperature decreases. The contrary is true if the reaction is exothermic; the reaction releases energy thus the temperature increases.
Photocell detecting light from plasma processing chamber.
A photocell is a sensor that can measure the intensity of light. Other light sensors are capable of measuring color (spectrum), or detecting modulated sources.
1M. V. Malyshev and V. M. Donnelly, "Determination of electron temperatures in plasmas by multiple rare gas optical emission, and implications for advanced actinometry," Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, vol. 15, no. 3, pp. 550-558, 1997.
Processing plasma discharge producing detectable light signature.1
Plasma processing is a key technology used in many industries for coating materials from sunglasses, to LCD screens and solar panels. One novel application of light detection is employed to measure the temperature of a processing plasma discharge. Directly measuring a plasma discharge electrically perturbs the discharge itself, so using optical detection method is prefered when permissible. To do so, a DAQ system could be used to collect light intensity at certain wavelengths to determine the excitation signatures of specific noble gasses in the discharge. A Nyquist DAQ device and a few photo sensors (with bandpass coating) could serve this purpose with little physical setup. This could replace thousands of dollars worth of spectroscopy equipment.
Common Omnidirectional Electret Condenser Microphone1
An important application of sound data acquisition is monitoring sound levels in the workplace. The Occupational Safety and Health Administration (OSHA) limits the maximum sound levels and the duration at which sound levels can be sustained. For example, OSHA limits sound levels at 90 dBA to 8 hours. 100 dBA is limited to 15 minutes. For every 3 decibels over 85 dbA, the allowed exposure time is decreased by half. By using a data acquisition system coupled with a microphone, employers can ensure they don't exceed OSHA limitations.
Sound frequency (Hz) and sound intensity (dB) can be directly measured with an appropriate sensor and DAQ. The microphone is a well known sensor to convert sound waves into analog electrical signals. Often modern compact microphone assemblies contain an amplifier to convert the mechanical vibration mode (electret, piezo, or coil) to a measurable voltage. This voltage can then be logged directly by a DAQ or amplified, filtered or integrated for a particular application. Afterward the data logged by the DAQ can be converted into the frequency domain for further analysis or even simply recorded for playback.
1Occupational Safety & Health Administration [OSHA], "OSHA Technical Manual - Noise," 2013.
A simple application of a flow sensor and data acquisition system can be used to monitor the performance of HVAC systems. If the flow performance rapidly degrades, it could be an indicator that there is a problem with the system and isn't operating as efficiently as it should be.
Commercial air flow transducer for HVAC system.1
There are many sensors that measure flow from residential water meters to chemically reactive gas mass flow controllers (MFCs). Flow is measured in a rate and each sensor or controller is typically calibrated for a particular gas or liquid. The output (generally voltage) is proportional to the calibrated metric. This voltage is recorded and processed by the DAQ and software. Flow controllers have the added functionality to maintain a set flow rate as programmed by an input voltage. The DAQ would then set a flow rate using an analog output port and measure the resultant flow with an analog input port. MFCs are generally controlled using 0-5V, 0-10V, or serial RS-232 signals.
Mass flow controller (MFC) internal diagram.2
Expanding on the mass flow controller concept, a chemical engineer could use a DAQ to measure and control a set of MFCs for a chemical deposition process. Typically, such a process would use a "recipe" to control a temperature, plasma, or other energy source as well as a host of MFCs to produce a chemical coating or film. Once wired to the DAQ, the MFCs would be able to meter the gasses flowing through them and control the rate using a proportional valve and feedback loop. The loop's input variable would be a voltage from the DAQ as a flow rate set point. For example, 1V signal from the DAQ to the MFC might allow 100 standard cubic centimeters per minute (SCCM) of gas to flow into the reaction chamber.
1Courtesy of Eldridge Products, Inc, http://www.epiflow.com/
2Courtesy of Horiba, http://www.horiba.com/
A load cell is the sensor that can measure force applied to it. It converts the force to an electrical system for a data acquisition system to record.
A common use of measuring force is for laboratory and industrial scales. Another popular use is in industrial robotics for tactile sensing. This is important in material handling applications. Too much force and the payload could be damaged. Not enough force and the robot won't be able to pick up the payload.
Position & Displacement+
A popular position sensor is an ultrasonic transducer. Ultrasonic transducer converts ultrasonic waves to an electrical signal. Another popular position sensor in industrial settings is an Eddy current sensor. These sensors thrive in extreme environments (low/high temperature, dirty, or high pressure).
In the automotive industry, ultrasonic sensors are frequently used to measure the distance between the vehicle and an object. This makes a useful backup sensor.
Eddy current sensors can be used to monitor the vibration of rotating shafts. Logging these vibrations is important as increased vibrations could be a sign of upcoming failure.
We are all familiar with acceleration. Acceleration is the rate of change of velocity over time. An accelerometer is the sensor used for measuring acceleration.
There are many reasons one would be interested in measuring acceleration. For example, designers of autonomous vehicles want smooth acceleration and deceleration to minimize any jerky actions of the vehicle. Autonomous vehicles, especially those in development, are equipped with data acquisition systems to measure how the vehicle responds to the accelerator and brake input.
Acidity and alkalinity are measured in a unit called pH (potential of hydrogen). It is measured on a scale of 0 to 14 with 0 being the most acidic, 7 being neutral, and 14 being the most alkaline. This scale is a logarithmic scale, meaning a pH level of 4 is 10 times more acidic than a pH level of 5.
The proper pH of an aquarium is paramount to the well-being of the fishing living in it. Acidity of the water needs to remain at the correct level without big fluctuations or swings. By using data acquisition, one can monitor the pH levels of their aquarium. If data acquisition shows the pH levels are trending down, corrective action can be taken to bring the pH back up and stabilize it.
Swimming pools need to monitor their pH levels over time as well. The ideal pH of a swimming pool is 7.4 as this is the pH level of the human eye. In other words, maintaining a pH of 7.4 will minimize irritation and burning of the eyes. If the pH drops too low, damage could occur to the pool itself. If the pH is too high the water can become cloudy. The effectiveness of chlorine also drops with a high pH.
Combinations of Sensors+
It's often the case that multiple types of sensors are needed to give an understand of the physical world. For instance, a farmer who wanted to monitor the condition of their crop would want to use a combination of moisture sensors, pH sensors, and light sensors. By using this data, the farmer could ensure the crop has the correct amount of moisture, ideal pH levels, and is receiving the proper amount of sunlight.