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Chapter 2 DAQ System Overview
Signal Conditioning
Most computer-based measurement systems involve plug-in data acquisition (DAQ) devices
with some form of signal conditioning. Sensors and transducers usually require signal
conditioning before a measurement system can effectively and accurately acquire the signal. The
front-end signal conditioning system can include functions such as signal amplification,
attenuation, filtering, electrical isolation, simultaneous sampling, and multiplexing. In addition,
many transducers require excitation currents or voltages, bridge completion, linearization, or
high amplification for proper and accurate operation.
Sensors and Transducers
Sensors generate electrical signals to measure physical phenomena, such as temperature, force,
sound, or light. Strain gauges, thermocouples, thermistors, angular encoders, linear encoders,
and resistance temperature detectors (RTDs) are commonly used sensors.
To measure signals from these various transducers, you must convert them into a form that a
DAQ device can accept. For example, the output voltage of most thermocouples is very small
and susceptible to noise. You may need to amplify or filter the thermocouple output before
digitizing it. The manipulation of signals to prepare them for digitizing is called signal
conditioning.
For more information about sensors, refer to the following documents:
• For general information about sensors, visit
ni.com/sensors.
• If you are using LabVIEW, refer to the LabVIEW Help by selecting Help»Search the
LabVIEW Help in LabVIEW and then navigate to the Taking Measurements book on
the Contents tab.
Table 2-3. USB Device Accessories, Power Supply, and Ferrite
Description Part Number
Universal power supply with mini-combicon
connector, 12 VDC, 2.5 A
781513-01
USB X Series mounting kit with DIN rail clip* 781515-01
USB X Series mounting kit* 781514-01
USB X Series lid with thumbscrew fasteners 781661-01
USB cable with locking screw, 2 m 780534-01
EMI suppression ferrites, 10.2 mm length 781233-02
*
Not for use with NI USB BNC devices.
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