What is gain error in a DAC?
-
missing codes -
error in the slope of the output staircase waveform -
more or less input voltage is required for the first step than what is specified
Two principal advantages of the dual-slope ADC are its:
-
high speed and low cost. -
high sensitivity to noise and low cost. -
low sensitivity to noise and high speed. -
low sensitivity to noise and low cost.
The process by which a computer acquires digitized analog data is referred to as ________.
-
data acquisition -
monotonicity -
analog resolution -
systematic digital conversion
Describe offset error for a DAC.
-
missing codes -
error in the slope of the output staircase waveform -
more or less input voltage is required for the first step than what is specified
What is the speed of the up/down digital-ramp ADC (tracking ADC)?
-
20 
s -
10 s -
1 s -
Relatively slow
The practical use of binary-weighted digital-to-analog converters is limited to:
-
R/2R ladder D/A converters -
4-bit D/A converters -
8-bit D/A converters -
op-amp comparators
The practical use of binary-weighted digital-to-analog converters is limited to:
-
R/2R ladder D/A converters -
4-bit D/A converters -
8-bit D/A converters -
op-amp comparators
________ are the most linear of all the temperature transducers.
-
Thermistors -
Thermocouples -
IC temperature sensors -
Resistance temperature detectors
What is the major advantage of the R/2R ladder DAC as compared to a binary-weighted-input DAC?
-
It has fewer parts for the same number of inputs. -
It is much easier to analyze its operation. -
It uses only two different resistor values. -
The virtual ground is eliminated and the circuit is therefore easier to understand and troubleshoot.
An analog-to-digital converter has a four-bit output. How many analog values can it represent?
-
4 -
1/4 -
16 -
0.0625
When comparing the conversions from digital-to-analog and analog-to-digital, the A/D conversion is generally:
-
less complicated but more time consuming than the D/A conversion. -
more complicated and more time consuming than the D/A conversion. -
less complicated and less time consuming than the D/A conversion. -
more complicated but less time consuming than the D/A conversion.
________ are the most linear of all the temperature transducers.
-
Thermistors -
Thermocouples -
IC temperature sensors -
Resistance temperature detectors
What is one advantage to using a parallel-encoded (flash) ADC?
-
less expensive -
very fast conversion -
less complicated circuit
Which of the statements below best describes the basic operation of a dual-slope A/D converter?
-
The input voltage is used to set the frequency of a voltage-controlled oscillator (VCO). The VCO quits changing frequency when the input voltage stabilizes. The frequency of the VCO, which is proportional to the analog input voltage, is measured and is displayed on the digital display as a voltage reading. -
A ramp generator is used to enable a counter through a comparator. When the ramp voltage equals the input voltage, the counter is latched and then reset. The counter reading is proportional to the input voltage since the ramp is changing at a constant V/second rate. -
A ramp voltage and analog input voltage are applied to a comparator. As the input voltage causes the integrating capacitor to charge, it will at some point equal the ramp voltage. The ramp voltage is measured and displayed on the digital panel meter. -
Two ramps are generated: one by the input voltage and the other by a reference voltage. The input voltage ramp charges the integrating capacitor, while the reference voltage discharges the capacitor and enables the counter until the capacitor is discharged, at which time the counter value is loaded into the output latches.
The main advantage of the successive-approximation A/D converter over the counter-ramp A/D converter is its:
-
more complex circuitry -
less complex circuitry -
longer conversion time -
shorter conversion time
What is the linearity of a D/A converter?
-
It is the reciprocal of the number of discrete steps in the D/A output. -
It is the comparison between the actual output of the converter and its expected output. -
It is the converter's ability to resolve between forward and reverse steps when sequenced over its entire range of inputs. -
It is the deviation between the ideal straight-line output and the actual output of the converter.
The basic approach to testing D/A converters is to:
-
apply a sequence of binary codes covering the full range of input values to the circuit input while observing the output on an oscilloscope. The output should consist of a linear stairstep ramp. -
single-step the device through its full input range while checking the output with a DMM. -
check the output with zero input and then full input. The output of the converter should extend from zero to its maximum value. If so, then everything in between can be assumed to be operating properly. -
apply the correct input to the analog terminal and then check to see if the proper binary code exists on the digital inputs.
If the same analog signal is to be converted to an 8-bit resolution using a counter-ramp ADC, how many comparator circuits would be used?
-
1 -
8 -
127 -
255
The output of a basic 4-bit input digital-to-analog converter would be capable of outputting:
-
16 different values of voltage or current that are not proportional to the input binary number -
16 different values of voltage or current that are proportional to the input binary number -
32 different values of voltage or current that are not proportional to the input binary number -
32 different values of voltage or current that are proportional to the input binary number
The quantization error in an analog-to-digital converter can be reduced by:
-
increasing the number of bits in the counter and DAC. -
decreasing the number of bits in the counter and increasing the number of bits in the DAC. -
increasing the number of bits in the counter and decreasing the number of bits in the DAC. -
decreasing the number of bits in the counter and DAC.
What is the maximum conversion time for a counter-ramp ADC with 8-bit resolution and a clock frequency of 20 kHz?
-
12.8 ms -
6.4 ms -
0.05 ms -
0.4 ms
One major difference between a counter-ramp A/D converter and a successive-approximation converter is:
-
the counter-ramp A/D converter is much faster than the successive-approximation converter -
with the successive-approximation converter the final binary result is always slightly less than the equivalent analog input, whereas with the counter-ramp A/D converter it is slightly more -
with the successive-approximation converter the final binary result is always slightly more than the equivalent analog input, whereas with the counter-ramp A/D converter it is slightly less -
none of the above
What is the major advantage of the R/2R ladder D/A converter as compared to a binary-weighted D/A converter?
-
It has fewer parts for the same number of inputs. -
It is much easier to analyze its operation. -
It uses only two different resistor values. -
The virtual ground is eliminated and the circuit is therefore easier to understand and troubleshoot.
One disadvantage of the tracking A/D converter is:
-
that it requires two counters—one for up and one for down. -
that the binary output will oscillate between two binary states when the analog input is constant. -
the need for an accurate clock reference for the counter. -
the need for a latch and its associated control circuit.
The primary disadvantage of the simultaneous A/D converter is:
-
that it requires the input voltage to be applied to the inputs simultaneously -
the long conversion time required -
the large number of output lines required to simultaneously decode the input voltage -
the large number of comparators required to represent a reasonable sized binary number
What is the disadvantage to using a counter-ramp type ADC?
-
complex circuit -
high cost -
very slow
A test system using the GPIB is being used to monitor a potentially dangerous crash test from a distance of 200 feet. The engineer decides to have you fabricate a special cable, rather than order one, since all the materials are on hand and the tests are already behind schedule. When the tests are run, the test system is erratic and the data is almost useless. What has gone wrong?
-
The engineer is probably not using the correct data format for the specific instruments being used to collect the data. -
The GPIB cable is too long; a bus extender should be used. -
The cable should be shielded and properly grounded. -
The tests themselves probably produced extraneous signals that confused the instruments, resulting in unusable data.
Which of the following characterizes an analog quantity?
-
Discrete levels represent changes in a quantity. -
Its values follow a logarithmic response curve. -
It can be described with a finite number of steps. -
It has a continuous set of values over a given range.
What is the main disadvantage of the stairstep-ramp A/D converter?
-
The counter must count up from zero at the beginning of each conversion sequence, and the conversion time will vary depending on the input voltage. -
It requires a counter. -
It requires a precision clock in order for the conversion to be reliable. -
All of the above
What is the disadvantage to using a counter-ramp type ADC?
-
complex circuit -
high cost -
very slow