18 Questions
What component sequentially switches between different analog input channels in a data acquisition system?
Analog multiplexer
What circuit acquires the signal voltage and holds its value during the connection time in a data acquisition system?
Sample and Hold circuit
Which component is responsible for timing and controlling the complete data acquisition system?
Programmer sequencer
In a data acquisition system, what is the primary objective related to acquiring the necessary data?
Acquire at the correct speed
When is Analog DAS commonly used in data acquisition systems?
When wide frequency width is required
What type of counter can count up as well as count down in a data acquisition system?
Up-down counter
In the given algorithm, what happens if Vin is less than VDAC at any cycle?
MSB is reset to 0
What is the purpose of the Successive Approximation Register (SAR) in the described algorithm?
To determine the binary count
How many cycles are required for an N-bit conversion using the described algorithm?
$N+1$
What advantage does the described algorithm have over other ADC types?
Medium accuracy with a good balance between speed and cost
When performing a 5-bit ADC conversion as in Example 1, what is the value of VDAC on Cycle 4?
$0.5625V$
What type of data conversion does the described algorithm perform?
Parallel to serial
What is the purpose of a Multiplexer (MUX) in the context provided?
To select and pass data bits serially based on a counter
What happens to the data byte after 8 CLK pulses in the described process?
It is changed to a serial format and sent out through the transmission line
In the context provided, what is the function of an Analog to Digital Converter (ADC)?
Converts a signal from analog to digital form
How many steps are involved in the process of Analog to Digital Conversion mentioned in the text?
3 - Quantizing, Sampling, Encoding
What does a Sampling and Holding circuit do in the context provided?
Samples and freezes the value of an analog signal for a specified period
What role does the counter play in the process described in the text?
It controls the conversion of parallel data to serial data
Study Notes
Data Acquisition System
- The first 8-bit group of parallel data is applied to the inputs of the MUX, and each bit is serially selected and passed through the MUX to the output line.
- After 8-CLK pulses, the data byte has been converted to a serial format and sent out through the transmission line.
Analog to Digital Converter (ADC)
- An ADC is an electronic integrated circuit that converts a signal from analog to digital form.
- ADC provides a link between the analog world of transducers and the digital world of signal processing and data handling.
Process of Analog to Digital Conversion
- The process involves three steps: sampling and holding, quantizing, and encoding.
- Sampling and holding involves sampling the voltage of a continuously varying analog signal and holding its value at a constant level for a specified minimum period of time.
- Quantizing involves breaking down the analog value into a set of finite states.
- Encoding involves assigning a digital word or number to each state and matching it to the input signal.
Sampling and Holding Circuit
- The circuit is an analog device that samples the voltage of a continuously varying analog signal and holds its value at a constant level for a specified minimum period of time.
- The processed analog signal is given to an analog multiplexer, which switches sequentially between a number of different analog input channels.
- Each input is connected to the output of the multiplexer for a specified period of time, and a sample-hold circuit acquires the signal voltage and holds its value while an A/D converter converts the value into digital form.
Objectives of Data Acquisition System
- The system must acquire the necessary data at the correct speed.
- The system must use all data efficiently to inform the operator about the state of the input.
- The system must monitor the complete plant operation to maintain online optimum and safe operation.
- The system must be able to summarize and store data for diagnosis and record purposes.
- The system must be flexible and capable of being expanded for future requirements.
- The system must provide an effective human communication.
Application of Data Acquisition System
- Analog DAS is used when wide frequency width is required or when lower accuracy can be tolerated.
Elements of Data Acquisition System
- DAC = Digital to Analog Converter
- EOC = End of Conversion
- SAR = Successive Approximation Register
- S/H = Sample and Hold Circuit
- Vin = Input Voltage
- Comparator Vref = Reference Voltage
Successive Approximation Register (SAR) Algorithm
- The algorithm uses an n-bit DAC and original analog results.
- It performs a binary comparison of VDAC and Vin.
- MSB is initialized at 1 for DAC.
- If Vin < VDAC (VREF / 2^n), then MSB is reset to 0.
- If Vin > VDAC (VREF / 2^n), then the successive bits are set to 1; otherwise, 0.
- The algorithm is repeated up to LSB.
- At the end, DAC in = ADC out.
- N-bit conversion requires N comparison cycles.
Advantages of SAR ADC
- Capable of high speed and reliable operation.
- Medium accuracy compared to other ADC types.
- Good trade-off between speed and cost.
- Capable of outputting the binary number in serial (one bit at a time) format.
This quiz covers the process of converting an 8-bit parallel data into a serial format utilizing a Multiplexer (MUX) and counter. The data is serialized by selecting each bit sequentially through the MUX and sent out through a transmission line after 8 clock pulses. The process repeats for each byte of data.
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