Data Acquisition Computer Boards

Data acquisition computer boards are self-contained printed circuit boards (PCBs) that plug into backplanes and motherboards, or interface directly with computer buses. They receive multiple electrical or electronic inputs from devices such as sensors and translate analog data into a digital format that computers can process. Data acquisition computer boards are an integral part of data acquisition systems for monitoring, analyzing, and/or controlling systems and processes. These devices include random access memory (RAM) and can include software that supports real time graphing, mathematical functions such as averaging, and statistical calculations such as deviation. 

Data acquisition computer boards can receive AC voltage, DC voltage, AC current, DC current, charges from piezoelectric devices, and frequency inputs. These PCBs work with accelerometers, thermocouples, thermistors, resistance temperature detectors (RTDs) and strain gauges, as well as with linear rotary and variable differential transformers (LVDTs and RVDTs). Data acquisition computer boards can also receive specialized inputs from encoders, tachometers, timers, and relays. Some data acquisition computer boards output voltage such as 0 – 10 V or current loops such as 0 – 20 mA. Other devices output frequencies such as AM or FM. Timer, counter, relay, and resistance outputs are also available.  

There are several types of analog-to-digital converters (ADC) for data acquisition computer boards. Flash ADCs apply the input in parallel to many fast comparators whose thresholds are spaced equally throughout a range of input voltages. Half-flash ADCs combine the results of two sequentially performed, lower-resolution flash conversions to determine the output code. Integrator ADCs provide an output code that represents the average value of the input voltage over a time interval. Successive approximation ADCs sequentially compare a series of binary-weighted values with an analog input to produce an digital output in a series of steps. Voltage-to-frequency ADCs convert an input voltage to an output pulse train with a frequency proportional to the input voltage. Delta sigma circuits sample at a rate and frequency that pushes the quantization noise out of range.  

Data acquisition computer boards include integral, multi-pole, analog and digital filters that support a variety of functions. Some devices provide programmable, anti-aliasing filters that include a low pass cutoff frequency and a high pass cutoff frequency. Filter types include Bessel, Butterworth, Cauer, Chebyshev, and linear phase. Cauer and Chebyshev filters provide a relatively fast response or roll-off. Bessel and Butterwoth filters do not. Linear phase response filters preserve the phase characteristics of a signal by time-delaying the signal components equally. Low pass, high pass, band pass, band stop, and all pass filters are available. In addition, some data acquisition computer boards include an integral amplifier with programmable gain and a variable bandwidth.

Data acquisition computer boards work with computer bus types such as universal serial bus (USB), peripheral component interconnect (PCI), and industry standard architecture (ISA). They support numerous network typologies, including Ethernet, DeviceNet, and smart distributed system (SDS). Data acquisition computer boards are used in a variety of environmental, vehicular, marine, aerospace, military, seismic, and meteorological applications. They are also used in medical imaging applications that use cameras, and in biomedical applications.

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