Data acquisition is the process of digitizing data from the world around us so it can be displayed, analyzed, and stored in a computer. To help you choose the right tool for your application, we have a complete guide to DAQ systems in 2018 on our website. Let’s go over the basic components of a DAQ system, and if you want more information about the various options for your application, check out the full post at mccdaq.com/data-acquisition.
Components of a Data Acquisition System
All data acquisition systems consist of three essential elements – Sensor, Signal Conditioning, and Analog-to-Digital Converter (ADC).
At the core of all data acquisition systems is an Analog to Digital Converter (ADC). As the name implies, this chip takes data from the environment and converts it to discrete levels that can be interpreted by a processor. These discrete levels correspond to the smallest detectable change in the signal being measured. The higher the number of “bits” of an ADC (12-bit, 16-bit, 18-bit etc.), the greater the number of discrete levels that can represent an analog signal and the greater the resolution of the ADC. The resolution of an ADC is essentially analogous to the ticks on a measuring stick. A measuring stick with mm tick marks has more resolution than a measuring stick with only cm tick marks. Whether you need mm or cm tick marks depends on what you are measuring – the same is true for ADC resolution.
Sensors, often called Transducers, convert real-world phenomenon like temperature, force, and movement to voltage or current signals that can be used as inputs to the ADC. Common sensors include thermocouples, thermistors, and RTDs to measure temperature, accelerometers to measure movement, and strain gauges to measure force. When choosing the right sensor for your measurement system, it’s important to consider factors like the accuracy of the sensor and the signal conditioning required to record a readable signal.
To make quality measurements on transducers, additional circuitry is often needed between the transducer and the ADC. This circuitry is generally referred to as signal conditioning and can include amplification/attenuation, filtering, Wheatstone bridge completion, excitation, linearization, calibration, and cold-junction-compensation (CJC). Different sensors have different signal conditioning needs. For instance, signal conditioning for a strain gauge requires excitation, bridge completion and calibration. Thermocouples, which output signals in the mV range, need to be amplified as well as filtered before going through the ADC.Many times, signal conditioning circuitry is contained within a data acquisition device, but signal conditioning may also be part of the transducer. Load cells, for example, contain the bridge completion, calibration circuitry, and amplification. Many MEM (micro-electro-mechanical) sensors also contain signal conditioning.
For more information, go to mccdaq.com/data-acquisition.