Introduction to DIGITAL INSTRUMENTATION
Digital instrumentation:
In digital instrumentatio as we have, all the transducers considered so far have had an analog outcome, that is the outcome is a different kind from the views but its value is appropriate to the value of the views. Why should we go to the real and costs of transferring an analog signal into a digital one in which the outcome quantity is personalized into a series of existing yearnings composed its statistical equivalent? The objective is precise. Once a quantity has been indicated as a wide range it cannot change its value like an analog sign may do while it is being ready. Also, if the sign is indicated in binary analysis, the managing can be done numerically in a micro-processor or pc. An analog signal is become a digital one by sampling,
In digital instrumentatio as we have, all the transducers considered so far have had an analog outcome, that is the outcome is a different kind from the views but its value is appropriate to the value of the views. Why should we go to the real and costs of transferring an analog signal into a digital one in which the outcome quantity is personalized into a series of existing yearnings composed its statistical equivalent? The objective is precise. Once a quantity has been indicated as a wide range it cannot change its value like an analog sign may do while it is being ready. Also, if the sign is indicated in binary analysis, the managing can be done numerically in a micro-processor or pc. An analog signal is become a digital one by sampling,
- sampling theorem : that convert an analog signal into digital samples and convert them back into original signal provided the number of samples per second is more than twice the highest frequency in the signal.
A continuous signal can be represented by completely and rebuit from a set of instantaneous measurements or samples of its voltage which are made at equal spaced times and The interval between such samples must be less than one-half of the period of the highest-frequency component in the signal.
Suppose the signal contains a higher frequency than we expected, so that in fact the number of samples per second is less than twice that frequency. We then get what is known as aliasing; the samples convert back into a false lower frequency.
- Analog to digital conversion?
As we know,The main types of A/D converter: single slope, dual slope, successive approximation and flash.
We can say that,The sample voltages from the sample-and-hold amplifier are converted into binary numbers by another integrated circuit, an analogue-to-digital converter (usually abbreviated to A/D converter).
- Digital to analog conversion?
here,It has as many inputs as there are digits in the binary numbers which represent the voltage values.
In digital to analog conversion,after transmission, processing, etc., the digital signal may have to be converted back to analog form. This is done by another integrated circuit: a digital-to-analog converter (D/A).
As we know that The D/A converter circuit, known as an R-2R ladder,
Each input operates its own electronic switch (a logic gate) which connects that particular leg of the ladder to the reference voltage, if the binary digit is a 1, or to earth if it is a 0. If all the legs but one are connected to earth, the one connected to the reference voltage produces a current which flows towards the inverting input of the op-amp and is halved by the resistance network at each junction through which it passes. Thus the current contribution of each leg is weighted to correspond to the position of that particular digit in the complete binary number; for example, in a 4-bit D/A converter the current produced by the most significant bit (MSB) will be 8 times (2(4-1)=8) the current produced by the least significant bit (LSB). an output voltage proportional to the sum of the currents it produces by The op-amp .
Post a Comment