Universiti Malaysia Perlis

1. Universiti Malaysia Perlis ENT356 INSTRUMENTATION SYSTEM Lecture 6: Introduction to Computer Data Acquisition System (DAQ) Sem 2, 2010/2011

2. Data Acquisition System? Data acquisition systems are products or processes used to collect information to document or analyze some phenomenon

3. 5 components vital when building/setup of a DAQ System • Sensors and Transducers A transducer is a device that converts a physical phenomenon into a measurable electrical signal, such as voltage or current. The ability of a DAQ system to measure different phenomena depends on the transducers to convert the physical phenomena into signals measurable by the DAQ hardware. Transducers are synonymous with sensors in DAQ systems.

4. 5 components vital when building/setup of a DAQ System (b)Signals The appropriate transducers convert physical phenomena into measurable signals. However, different signals need to be measured in different ways. For this reason, it is important to understand the different types of signals and their corresponding attributes. Signals can be categorized into two groups: ·Analog·Digital

5. 5 components vital when building/setup of a DAQ System (c) Signal Conditioning Sometimes transducers generate signals too difficult or too dangerous to measure directly with a DAQ device. For instance, when dealing with high voltages, noisy environments, extreme high and low signals, or simultaneous signal measurement, signal conditioning is essential for an effective DAQ system. Signal conditioning maximizes the accuracy of a system, allows sensors to operate properly, and guarantees safety.

6. 5 components vital when building/setup of a DAQ System (d) DAQ Hardware DAQ hardware acts as the interface between the computer and the outside world. It primarily functions as a device that digitizes incoming analog signals so that the computer can interpret them. Other data acquisition functionality includes:· Analog Input/Output· Digital Input/Output· Counter/Timers· Multifunction - a combination of analog, digital, and counter operations on a single device

7. 5 components vital when building/setup of a DAQ System (e)Driver and Application Software DriverSoftwareSoftware transforms the PC and the DAQ hardware into a complete data acquisition, analysis, and presentation tool. Without software to control or drive the hardware, the DAQ device will not work properly. Driver software is the layer of software for easily communicating with the hardware. It forms the middle layer between the application software and the hardware. Driver software also prevents a programmer from having to do register-level programming or complicated commands in order to access the hardware functions.

8. 5 components vital when building/setup of a DAQ System Application Software • The application layer can be either a development environment in which you build a custom application that meets specific criteria, or it can be a configuration-based program with preset functionality. Application software adds analysis and presentation capabilities to driver software. To choose the right application software, evaluate the complexity of the application, the availability of configuration-based software that fits the application, and the amount of time available to develop the application. If the application is complex or there is no existing program, use a development environment.

9. common terms in DAQ System (a)Analog-to-digital converter ADC An electronic device that converts analog signals to an equivalent digital form (b)Digital-to-analog converter DAC An electronic component found in many data acquisition devices that produce an analog output signal

10. common terms in DAQ System (c) Digital input/output DIO Refers to a type of data acquisition signal. Digital I/O are discrete signals which are either one of two states: on/off, high/low, 1/0, etc (d) Single Ended input Refers to the way a signal is wired to a data acquisition device. In single-ended wiring, each analog input has a unique high connection but all channels share a common ground connection

11. Resolution The smallest signal increment that can be detected by a data acquisition system. For example, a system has 12-bit resolution, one part in 4,096 resolution, or 0.0244 percent of full scale Sample rate The speed at which a data acquisition system collects data. Normally expressed in samples per second. For multi channel data acquisition devices the sample rate is typically given as speed of ADC. To obtain individual channel sample rate, you need to divide the speed of the A/D by number of channels being sample

12. RS 232 A standard for serial communications found in data acquisition system. Limitation is it support communication to one device to the bus at a time and only supports transmission distances up to 50 feet RS 485 A standard for serial communications found in many data acquisition system. RS 485 is more flexible which supports communication to more than one device on the bus at a time and supports transmission distances of approximately 5000 feet

13. differences between 5 common types of DAQ System

14. Basic DAQ system purpose: To acquire data from temperature sensor RTD, store and analyze in desktop PC

15. Thank you