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14:43:50 Page 283
A three-digit display rounds E 0 to 6.38 V. The difference between the input and output values is
attributed to quantization error. With a clock speed of 100 kHz, each ramp step requires 10 ms/step,
and conversion time ¼ 653 steps  10 ms/step ¼ 6530 ms.
COMMENT A similar dual-ramp converter would require twice as many steps and twice the
conversion time.
7.6 DATA-ACQUISITION SYSTEMS
A data-acquisition system is the portion of a measurement system that quantifies and stores data.
There are many ways to do this. The engineer who reads a transducer dial, associates a number with
the dial position, and records the number in a log book, performs all of the tasks germane to a dataacquisition system. This section focuses on microprocessor-based data-acquisition systems, which
are used to perform automated data quantification and storage.
Figure 7.12 shows how a data-acquisition system (DAS) might fit into the general measurement
scheme between the actual measurement and the subsequent data reduction. A typical signal flow
scheme is shown in Figure 7.13 for multiple input signals to a single microprocessor-based/
controller DAS.
Dedicated microprocessor systems can continuously perform their programming instructions to
measure, store, interpret and provide process control without any intervention. Such microprocessors
Data
reduction
Digital
form
Analog
Voltage
Current
Power
Force
etc.
Physical
variable
Transfer
Convert
Convert
Postprocessing
Data-acquisition system
Transducer
Figure 7.12 Typical signal and
measurement scheme.
Multiplexer
Digital
inputs
Signal
conditioning
Analog
transducers
Buffer
Clock
Controller
External
computer
Display
Process
feedback
Storage
Analog-todigital
converter
Figure 7.13 Signal flow scheme for an automated data-acquisition system.
7.6 Data-Acquisition Systems 283
14:43:50 Page 283
A three-digit display rounds E 0 to 6.38 V. The difference between the input and output values is
attributed to quantization error. With a clock speed of 100 kHz, each ramp step requires 10 ms/step,
and conversion time ¼ 653 steps  10 ms/step ¼ 6530 ms.
COMMENT A similar dual-ramp converter would require twice as many steps and twice the
conversion time.
7.6 DATA-ACQUISITION SYSTEMS
A data-acquisition system is the portion of a measurement system that quantifies and stores data.
There are many ways to do this. The engineer who reads a transducer dial, associates a number with
the dial position, and records the number in a log book, performs all of the tasks germane to a dataacquisition system. This section focuses on microprocessor-based data-acquisition systems, which
are used to perform automated data quantification and storage.
Figure 7.12 shows how a data-acquisition system (DAS) might fit into the general measurement
scheme between the actual measurement and the subsequent data reduction. A typical signal flow
scheme is shown in Figure 7.13 for multiple input signals to a single microprocessor-based/
controller DAS.
Dedicated microprocessor systems can continuously perform their programming instructions to
measure, store, interpret and provide process control without any intervention. Such microprocessors
Data
reduction
Digital
form
Analog
Voltage
Current
Power
Force
etc.
Physical
variable
Transfer
Convert
Convert
Postprocessing
Data-acquisition system
Transducer
Figure 7.12 Typical signal and
measurement scheme.
Multiplexer
Digital
inputs
Signal
conditioning
Analog
transducers
Buffer
Clock
Controller
External
computer
Display
Process
feedback
Storage
Analog-todigital
converter
Figure 7.13 Signal flow scheme for an automated data-acquisition system.
7.6 Data-Acquisition Systems 283