Data Acquisition Hardware Overview

Data Acquisition Hardware

• Data Acquisition (DAQ) systems capture real-world signals and convert them into digital information for computers to process.
• A DAQ system typically comprises three main components: a terminal block, a cable, and a DAQ device.
  • The terminal block provides physical connections for signals.
  • The cable transmits the signal from the terminal block to the DAQ device.
  • The DAQ device acquires the signal and transforms it into a format the computer can understand.
• DAQ devices are available in several forms, including PCI, PCMCIA, USB, and Ethernet.
  • The choice of bus structure depends on the specific application requirements in terms of data transfer rate, portability, and connection distance.
• The NI BNC-2120 is a convenient connector block with labeled BNC connectors for connecting analog signals to NI DAQ devices.

DAQ Device Components

• Computer I/O Interface Circuitry: Facilitates data transfer between the DAQ device and the computer.
• I/O Connector: Connects the terminal block to the DAQ device.
• Real-Time System Integration (RTSI) Bus: Enables communication and signal synchronization between multiple DAQ devices connected to the same computer.

Analog Input Circuitry

• Multiplexer: Selects one input channel at a time to connect to the instrumentation amplifier.
• Instrumentation Amplifier: Amplifies or attenuates the signal to ensure proper range for the ADC.

Analog-to-Digital Converter (ADC)

• Converts an analog voltage signal into a digital number for computer interpretation.
• The ADC's resolution, determined by the number of bits used, dictates the accuracy of the conversion.
• Analog input circuitry and the ADC work together to acquire analog signals for measuring level, shape, and frequency.

Analog Output Circuitry

• Digital-to-Analog Converter (DAC): Converts a digital number from the computer into an analog signal, output through the I/O connector.
• DACs are useful for generating DC signals, specific tones, and waveforms.

Digital I/O Circuitry

• Performs both input and output functions.
• Can acquire or generate digital signals using software or hardware timing.
• Applications range from monitoring switch states to controlling relays.

Counter Circuitry

• Acquires and generates digital signals.
• Utilizes internal timing signals (timebases) for measuring signal rates.
• Typical applications include measuring motor shaft frequencies and controlling stepper motors.

Choosing Appropriate DAQ Hardware

• Consider the following factors:
  • Bus of DAQ device: The bus impacts data transfer rate, latency, synchronizability, portability, and connection distance requirements.
  • Signals to measure: Determine the type and characteristics of the signals, such as code width and input range.
  • Accuracy of measurements: Resolution and ADC specifications affect the accuracy of the measurements.

Data Acquisition Software Overview

• DAQ software is essential to control DAQ hardware and process acquired data.
• National Instruments' NI-DAQmx provides user-friendly graphical VIs for configuring and operating DAQ devices.

Summary

• DAQ systems capture real-world signals, convert them into digital data, and transmit them to computers.
• The choice of DAQ hardware and software depends on the specific application requirements and signal characteristics. Understanding the fundamental components of DAQ devices is essential for building effective measurement and control systems.

This quiz explores the key components and functionalities of Data Acquisition (DAQ) systems. Learn about the terminal block, cable, and various types of DAQ devices including USB and Ethernet options. Understand how these systems convert real-world signals into digital information.