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Right answer is (b) it integrates the input twice

Easiest explanation: The input signal is integrated only for a fixed interval of time and this is the basis for the dual slope METHOD. REFERENCE VOLTAGE is integrated with a negative slope. HENCE the method is known as dual slope integrating TYPE DVM.

Correct choice is (a) no noise

To explain I would SAY: During the process of integration, noise is CANCELED out by the positive and NEGATIVE ramps in the dual slope method. The input SIGNAL is integrated only for a FIXED interval of time and this is the basis for the dual slope method.

Correct option is (d) high

For explanation I WOULD say: In a POTENTIOMETRIC INTEGRATING type DVM, the accuracy is usually high. It generally depends on the REFERENCE of the digital to analog converter. Accuracy of the voltage to frequency converter is less important compared to that of the digital to analog converter.

Right choice is (c) VOLTAGE magnitude

The explanation is: In a potentiometric integrating type DVM, the SLIDER moves based on the magnitude of the feedback voltage with RESPECT to the input voltage. Contact is pushed back to the place where the UNKNOWN voltage equals the feedback voltage.

The correct option is (a) COMPARATOR

Explanation: Comparator accepts the feedback VOLTAGE as an input. Comparator COMPARES the VALUES of the unknown voltage and the feedback voltage. Comparator then provides the difference between the feedback voltage and the unknown voltage as its output.

The CORRECT answer is (d) from a fixed voltage source

Easiest explanation: Reference voltage is applied to the potentiometer. It is OBTAINED from a source of fixed voltage. The position of the slider on the contact surface DETERMINES the VALUE of the feedback voltage.

The correct option is (c) FILTERED

For explanation: In a potentiometric integrated type DVM, the unknown voltage is filtered. It is also attenuated to a suitable magnitude. This forms the INPUT for the comparator. A chopper is usually used as an ERROR DETECTOR.

Correct choice is (B) False

The best explanation: Balance is obtained in a potentiometric INTEGRATING type DVM by adjusting the settings of the potentiometer. HENCE in a potentiometric integrating type DVM, the balance is obtained automatically.

Correct CHOICE is (c) magnitude and stability of pulse GENERATOR

Explanation: Accuracy of the VOLTAGE to frequency conversion depends on the capacity of the pulse generator to produce an electric charge with a suitable magnitude and stability. Hence the accuracy depends on the PRECISION of the charge FEEDBACK.

Right choice is (a) voltage is compared

Explanation: POTENTIOMETRIC INTEGRATING type DVM employs voltage comparison. The unknown voltage is compared with a REFERENCE. The reference value is set by a calibrated potentiometer.

Right ANSWER is (a) True

The best explanation: Each TOOTH in the sawtooth waveform produces a PULSE at the output of the pulse generator. HENCE the number of tooth i.e. the frequency is directly RELATED to the number of pulses.

Right answer is (a) True

The EXPLANATION is: The sawtooth output signal OBTAINED from the integrating type DVM is PASSED through a REVERSIBLE counter. A digital readout displays the value measured by the reversible counter.

Correct CHOICE is (a) directly proportional

The explanation is: When the INPUT signal in a voltage to frequency conversion TYPE INTEGRATED DVM is DOUBLED, the number of tooth in the output signal is doubled per unit time. This doubles the frequency of the output signal.

Right OPTION is (d) negative GOING ramp

To explain I would SAY: The op amp produces a negative going ramp signal for a positive input voltage. Capacitor is discharged after some time and the OUTPUT returns to zero. The next cycle STARTS and the output is a sawtooth waveform. Figure shows the output sawtooth waveform.

The correct answer is (b) counting PULSES

The best explanation: A pulse train is generated. Their FREQUENCY DEPENDS on the frequency of the unknown voltage. Number of pulses present in a definite interval are counted. Unknown INPUT voltage is a MEASURE of the pulses generated.

Correct answer is (c) op amp

To ELABORATE: An op amp forms the heart of the integrating TYPE DVM. Op amp is used as an INTEGRATOR. The input signal is INTEGRATED for a fixed interval giving rise to a RAMP signal at the output.

Right option is (a) voltage is CONVERTED to TIME

Easy explanation: We know that the QUANTITIES time and frequency are related to each other. Voltage is converted into time in a voltage to frequency converter type integrating DVM.

Correct CHOICE is (a) ±12 V

Easy explanation: In the linear ramp technique, a swing of ±12 V is produced by the ramp. This limits the effective voltage available to ±10 V considering the voltage drop ACROSS the COMPONENTS in the CIRCUIT.

Right answer is (d) 5 cycles/second

Explanation: A MULTIVIBRATOR has a typical value of 5 cycles/second. It has an ACCURACY of the order of ±0.005 %. The ramp generator STARTS the next ramp VOLTAGE based on the sample rate.

Correct option is (b) by counting the pulses

The explanation is: The electronic counter USED in the linear ramp TECHNIQUE counts the definite NUMBER of pulses during the start and end pulse. This COUNT is a measure of the input VOLTAGE signal.

The CORRECT option is (C) mutivibrator

Easiest explanation: Initiation of the measurement cycles is taken care of by the sample rate multivibrator. This vibrator OSCILLATES at the rate of 1000 cycles per SECOND. It is adjusted by a front panel CONTROL.

The correct CHOICE is (a) frequency

To elaborate: In the LINEAR ramp TECHNIQUE, resolution is dependent on the frequency of the local OSCILLATOR. By adjusting the frequency of the local oscillator the resolution of the linear ramp can be made higher.

Right answer is (b) time measurement

To explain I WOULD say: Linear ramp technique works on the PRINCIPLE of measurement of time required by a linear ramp to rise from 0 V to the INPUT voltage. It can also be the time required by the input voltage to FALL to 0 V.

Right answer is (d) linear ramp

To elaborate: The linear ramp technique essentially CONSISTS of a linear ramp. It is either POSITIVE or negative GOING. Range of the linear ramp varies from –12 V to +12 V. Base range varies from –10 V to +10 V.

Correct option is (b) False

For explanation I WOULD SAY: In a successive approximation type DVM, the ACCURACY is DEPENDENT on the internal reference supply. It also depends on the accuracy of the digital to analog converter that is used in the circuit.

Correct option is (c) SOLID state devices

The EXPLANATION is: Solid state devices can be used in order to INCREASE the SPEED of operation in a successive approximation type DVM. Electromechanical switches provide a low speed of operation.

Correct CHOICE is (b) S = fsmin × R

The best explanation: In a successive approximation type DVM, the sensitivity is given by the relation

S = fsmin × R

where, S is the sensitivity

R is the resolution

fsmin is the full SCALE reading when the RANGE is minimum.

Right answer is (d) generate sequence code

Easiest explanation: A COMPARATOR is used in a successive APPROXIMATION TYPE DVM so as to compare the output of the D/A converter with the unknown voltage. Logic control and sequencer TAKES the INPUT from the comparator and generates the sequence code.

The correct answer is (a) True

The EXPLANATION: If the output of the digital to analog converter BECOMES EQUAL to the unknown voltage in terms of magnitude, the D/A converter generates the set pattern of VOLTAGES successively.

The correct option is (a) of a digital divider

The explanation: Servo balancing type DVM makes use of a LINEAR divider in a potentiometer. In the case of a successive approximation type DVM we make use of a digital divider. A digital divider is BASICALLY a digital to analog CONVERTER.

Right option is (b) weight of an object

Explanation: A successive approximation TYPE DVM WORKS on the principle of measuring the weight of an object. It consists of an object on one of the sides of the balance and an APPROPRIATE weight on the other SIDE of the balance. The weight of the object is determined by SUCCESSIVELY adding and removing weights from the balance.

Correct option is (a) True

The explanation: Since it is difficult to follow the reading visually at high reading speeds, USER has to WAIT till a stable reading is OBTAINED. The DIGITIZING period depends on the MAXIMUM speed at which the value is read from the meter.

Correct option is (d) converts analog signal to digital

The EXPLANATION is: DVM converts analog signal to digital. The process is KNOWN as digitization and the CIRCUIT used to obtain the conversion is known as a digitizing circuit. Time needed for this conversion is known as digitizing PERIOD.

Correct CHOICE is (c) 3-6 DIGITS

The explanation is: The DVM consists of 3 to 6 digits. As the number of digits are INCREASED the RESOLUTION also increases. Thus, the resolution of a DVM is very high.

Correct option is (B) filtering

To explain: Filters can be used to ELIMINATE the normal mode NOISE SIGNALS. When used for low voltage measurement, noise present at the input can cause errors in the analog to digital CONVERTER.

Right choice is (a) 4 lines

The BEST EXPLANATION: Type of DVM used depends on the digital output lines. Four lines of BCD or a SINGLE line SERIAL output may be provided so as to READ the output from a DVM.

The correct choice is (c) high

For explanation I would say: Typical input impedance of a DVM is USUALLY very high. Typical VALUE is of the order of 10 MΩ. This is usually DONE in order to reduce the LOADING effect.

Right OPTION is (b) high

To elaborate: Accuracy of a DVM is based on the resolution. Resolution depends on the NUMBER of digits. The more the number of digits, the HIGHER is the accuracy. For a DVM, the accuracy is of the order of ±0.005 % of the reading.

The CORRECT CHOICE is (a) 1 or 10 V

Explanation: In a DVM, the basic range is 1 V or 10 V. Range of a DVM can be EXTENDED from a few µV to kV. This is ACHIEVED by making use of an attenuator.

Right ANSWER is (b) False

The explanation: The OUTPUT OBTAINED from a DVM can be used directly. It can be recorded and is ALSO suitable for further processing.

Right choice is (a) 1 V to 1000 V

For EXPLANATION I WOULD say: In a DVM, the INPUT voltage range is given as 1 V to 1000 V. It includes automatic range SELECTION and overload indication.