Latest Electronic Instruments ( Electrical Measurements ) MCQs – Electrical Measurements MCQs
Latest Electrical Measurements MCQs
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Electrical Measurements MCQs – Electronic Instruments ( Electrical Measurements ) MCQs
The most occurred mcqs of Electronic Instruments ( ) in past papers. Past papers of Electronic Instruments ( Electrical Measurements ) Mcqs. Past papers of Electronic Instruments ( Electrical Measurements ) Mcqs . Mcqs are the necessary part of any competitive / job related exams. The Mcqs having specific numbers in any written test. It is therefore everyone have to learn / remember the related Electronic Instruments ( Electrical Measurements ) Mcqs. The Important series of Electronic Instruments ( Electrical Measurements ) Mcqs are given below:
Advantages of Electronic Instruments
1. Electronic voltmeters use electronic circuits.
a) True
b) False
Answer: a
Explanation: Voltmeters that make use of rectifiers, diodes, amplifiers, etc in order to produce a current that is in proportion to the quantity that is being measured is known as an electronic voltmeter.
2. In olden days voltmeters were __________
a) made of transistors
b) made of vacuum tubes
c) made of transformers
d) made of diodes
Answer: b
Explanation: Initially, voltmeters were made of vaccum tubes. These voltmeters were known as vaccum tube voltmeters (VTVM).
3. Modern day voltmeters are made of __________
a) made of transformers
b) made of vacuum tubes
c) made of transistors and diodes
d) made of insulated iron coils
Answer: c
Explanation: Nowadays in voltmeters, transistors and semiconductor diodes are used. A transistor voltmeter makes use of transistor in a voltmeter.
4. FETVM is __________
a) an ammeter
b) a galvanometer
c) a multimeter
d) a voltmeter
Answer: d
Explanation: Field effect transistors can also be used at the input. Such voltmeters are known as FETVM (Field Effect Voltmeter).
5. Electronic voltmeters are __________
a) compact
b) large in size
c) not portable
d) difficult to use
Answer: a
Explanation: When compared to conventional analog voltmeters, electronic voltmeters are compact and also portable. This is due to the small size of the components.
6. Electronic voltmeters are not accurate.
a) True
b) False
Answer: b
Explanation: Compared to analog voltmeters, electronic voltmeters are very accurate and precise.
7. Electronic voltmeters are __________
a) dependent of frequency
b) dependent of voltage
c) independent of frequency
d) dependent of current
Answer: c
Explanation: Usually electronic voltmeters can measure frequency in the range of a few volts D.C. to frequencies of the order of hundreds of MHz. As a result, the effect of frequency on the response of electronic voltmeters is negligible.
8. Dynamic range of electronic voltmeter is __________
a) zero
b) limited
c) narrow
d) wide
Answer: d
Explanation: When compared to conventional analog voltmeters, the dynamic range is very wide and improved in electronic voltmeters. Very low as well as very high input signals can be measured using an electronic voltmeter.
9. Loading effect in electronic voltmeters is __________
a) nil
b) high
c) low
d) medium
Answer: a
Explanation: In an electronic voltmeter as the power is supplied by an external circuit, there is no loading effect. In a PMMC instrument, a minimum current of 50 µA is obtained from the signal that is to be measured and this leads to loading effect.
10. Electronic voltmeters are ____________
a) measure high level signals
b) measure low level signals
c) measure medium level signals
d) don’t measure any signal
Answer: b
Explanation: Electronic voltmeters make use of amplifier circuits. As a result they can be used for measuring low level signals.
Consideration in Selecting Voltmeter
1. Input impedance of a voltmeter is ___________
a) high
b) low
c) medium
d) zero
Answer: a
Explanation: In order to prevent the loading effect in a voltmeter, the input impedance is maintained as high as possible. It must be maintained higher than the impedance of the circuit being used.
2. Input impedance depends on _________
a) resistance
b) capacitance
c) inductance
d) voltage
Answer: b
Explanation: Shunt capacitance appearing across the input terminals affects the input impedance. Capacitive reactance of the capacitance is inversely proportional to the frequency.
Xc ∝ 1⁄f
where, Xc is the capacitive reactance
f is the frequency.
3. At high frequencies the capacitive reactance _________
a) is constant
b) increases
c) decreases
d) becomes zero
Answer: c
Explanation: We know that the capacitive reactance is inversely proportional to the frequency.
Xc ∝ 1⁄f
At high frequencies, the capacitive reactance becomes very small.
4. Voltage ranges in a meter are _________
a) 5-10-15
b) 20-50-100
c) 0.5-1-1.5
d) 1-3-10
Answer: d
Explanation: Meter scale will have a calibration of 1-3-10 for the voltage range with a separation of 10 dB. It can also be in the sequence of 1.5-5-15. We can also make use of a single scale.
5. Linear meter with 1% accuracy must have _________
a) 100 divisions
b) 50 divisions
c) 200 divisions
d) 500 divisions
Answer: a
Explanation: In order to recognize a reading with 1% accuracy it must have 100 divisions on the 1 V range.
6. Decibel covers a small range of values.
a) True
b) False
Answer: b
Explanation: As the unit decibel makes of the logarithmic scale, it covers a wide range of values of any given quantity.
7. Noise is a function of _________
a) voltage
b) current
c) bandwidth
d) frequency
Answer: c
Explanation: Noise in general depends on the value of the bandwidth. Voltmeter having a large bandwidth takes up more noise. Usually, the sensitivity of a voltmeter is 1mV for a bandwidth of 10Hz – 10MHz.
8. Current can be measured effectively by making use of _________
a) d.c. voltmeter
b) a.c. ammeter
c) d.c. ammeter
d) a.c. voltmeter
Answer: d
Explanation: By making use of an a.c. voltmeter in series with resistance we can obtain the current value. We can also make use of the current probe method to obtain the value of the current without effectively disturbing the circuit.
9. Average responding voltmeter is cheap and accurate.
a) True
b) False
Answer: a
Explanation: Average responding voltmeter is used for a.c. measurements for a sine wave with 10% distortion or less. Hence the average responding voltmeter is cheap and accurate.
Basic Electronic Voltmeter
1. Low voltage signals can be measured by ___________
a) amplifiers
b) transformers
c) transducers
d) voltmeters
Answer: a
Explanation: Electronic voltmeters make use of amplifiers to measure low voltage signals. It consists of two or more stages of D.C. amplifiers.
2. Input impedance of an electronic voltmeter is ________
a) low
b) high
c) medium
d) zero
Answer: b
Explanation: In an electronic voltmeter, the input impedance is maintained very high. This is achieved by making use of an FET (Field Effect Transistor) at the input of an electronic voltmeter.
3. Meter can be isolated from the circuit in a basic D.C. electronic voltmeter.
a) True
b) False
Answer: a
Explanation: Field effect transistor (FET) acts as a source follower and provides very high input impedance. BJT along with resistors form a balanced bridge circuit. As a result the meter circuit can be isolated from the main circuit.
4. Bridge is balanced by ________
a) galvanometer
b) oscillator
c) zero adjustment resistor
d) head phone
Answer: c
Explanation: Bridge circuit in a basic D.C. electronic voltmeter is balanced by making use of a zero adjustment resistor such that the pointer shows zero deflection.
5. What is the effect of the input on the transistor Q2?
a) bias on Q2 decreases
b) bias on Q2 is constant
c) bias on Q2 is zero
d) bias on Q2 increases
Answer: d
Explanation: The bias on the transistor Q2 increases when the input voltage is applied. As a result a proportional amount of current flows through the meter. Hence the deflection of the meter is directly proportional to the applied voltage within the dynamic range.
6. What is basic range of a meter?
a) causes maximum deflection
b) causes minimum deflection
c) causes zero deflection
d) causes medium deflection
Answer: a
Explanation: The input voltage that causes maximum deflection of the meter is known as the basic range of a meter. It occupies the lowest range on the range switch in the unamplified circuits.
7. High range can be obtained in a basic D.C. electronic voltmeter by ________
a) a transformer
b) an attenuator
c) a transducer
d) a resistor
Answer: b
Explanation: By making use of an attenuator in a basic D.C. electronic voltmeter, we get high range of values for the voltage reading. Attenuator is basically a voltage divider circuit with a predefined front panel.
8. Sensitivity of electronic voltmeter is high.
a) True
b) False
Answer: a
Explanation: In a PMMC voltmeter (Permanent Magnet Moving Coil), the sensitivity obtained is less and of the order of a few volts. In electronic voltmeters the sensitivity is very high and is of the order of at least 100 times as that compared to a PMMC voltmeter.
9. Overloading is ________
a) damages the meter
b) increases the temperature
c) doesn’t affect the meter
d) decreases the sensitivity
Answer: c
Explanation: As transistors saturate after a certain range of operating voltage and current, the value of the meter current is limited. As a result, overloading does not affect the meter and it remains safe.
True RMS Responding Voltmeter
1. R.M.S value means _________
a) root mean square
b) rate mean second
c) root median second
d) rate mode second
Answer: a
Explanation: R.M.S value indicates the Root Mean Square. It is obtained by taking the square root of the average value of the square of the input signal. It is also known as the effective value.
2. Meter reading is obtained by ________
a) sensing voltage
b) sensing heat power
c) sensing current
d) sensing resistance
Answer: b
Explanation: In a true R.M.S responding voltmeter, the meter reading is obtained by sensing the heat power of the waveform. The heat power is directly proportional to the r.m.s value of the input.
3. Measurement of heat power ________
a) uses a heat sink
b) uses a thermometer
c) uses a thermocouple
d) uses a black body
Answer: c
Explanation: A thermocouple is used to measure the heat power in a true R.M.S responding voltmeter. Input voltage under measurement is applied to the heater to which a thermocouple is also attached.
Measurement Of Power And Related Parameters MCQs
4. Sufficient heating of the heater is ensured by ________
a) increasing the temperature
b) making use of induction coil
c) amplifying d.c. input
d) amplifying a.c. input
Answer: d
Explanation: Maximum heating of the heater is obtained by making use of an amplified a.c. input. As a result the thermocouple generates maximum voltage level in order to cause the meter deflection.
5. Power in a thermocouple is given by ________
a) Power = E2 rms / Rheater
b) Power = E2 rms
c) Power = Rheater
d) Power = E2 rms × Rheater
Answer: a
Explanation: The power consumed in a thermocouple is given by the relation
Power = E2rms ⁄ Rheater
where, Erms is the r.m.s value of the a.c. input signal
Rheater is the resistance of the heater.
6. What is the main disadvantage of a true r.m.s responding voltmeter?
a) presence of transducer
b) presence of thermocouple
c) presence of transformer
d) presence of oscillator
Answer: b
Explanation: Thermocouples have non-linear voltage and current characteristics. This is the major drawback of the true r.m.s responding voltmeter. This is overcome in some instruments by making use of an additional thermocouple in the same thermal environment.
7. What is the naming convention for the two thermocouples?
a) thermocouple 1 and thermocouple 2
b) input thermocouple and output thermocouple
c) measuring thermocouple and balancing thermocouple
d) internal thermocouple and external thermocouple
Answer: c
Explanation: The thermocouple used in the input section of the voltmeter is known as the measuring thermocouple whereas the thermocouple used in the feedback path is known as the balancing thermocouple.
8. Sensitivity is of the order of ________
a) MV
b) V
c) GV
d) mV
Answer: d
Explanation: By making use of true r.m.s responding voltmeter we get the sensitivity of the order of mV. The voltage ranges from 100 µV to 300 V with a frequency range of 10 Hz to 100 MHz.
9. Response of thermocouples is fast.
a) True
b) False
Answer: b
Explanation: Crest factor limits the meter reading in a true r.m.s responding voltmeter when complex signals are taken into consideration. Also, the meter costs higher compared to average and peak responding meters. As a result the response of the thermocouples is slow.
Electronic Multimeter
1. Electronic multimeter measures ________
a) voltage, current and resistance
b) voltage and current
c) current and power
d) energy and power
Answer: a
Explanation: A.C. as well as D.C. voltage, current and resistance can be measured by making use of an electronic multimeter. It is also known as a voltage-ohm meter.
2. Basic circuit of multimeter consists ________
a) of a.c. amplifier
b) of d.c. amplifier
c) operational amplifier
d) power amplifier
Answer: b
Explanation: A.C. as well as D.C. voltage, current and resistance can be measured by making use of an electronic multimeter. The basic circuit of a multimeter is made up of d.c. amplifier circuit in the form of a balanced bridge.
3. Input signal magnitude is limited by ________
a) button
b) resistance
c) attenuator
d) voltage
Answer: c
Explanation: A range switch is provided in an electronic multimeter in order to limit the input signal in terms of magnitude. We can adjust the input attenuator and limit the input signal in terms of magnitude.
4. Electronic multimeter consists of a rectifier.
a) True
b) False
Answer: a
Explanation: An electronic multimeter is used for the measurement of A.C. as well as D.C. voltage, current and resistance. It consists of a rectifier section that is used to convert the a.c. input signal to d.c. voltage.
5. Multimeter can be used as an ammeter by ________
a) connecting series resistances
b) making use of a transducer
c) making use of a transformer
d) connecting shunts
Answer: d
Explanation: An electronic multimeter can be used as an ammeter by making use of shunt resistances across the meter. This is achieved by range selecting switch.
6. Multimeter can be used for D.C. voltage measurement by ________
a) connecting series resistances
b) connecting shunt resistances
c) connecting star delta resistances
d) using a switch
Answer: a
Explanation: We can obtain a wide range of D.C. voltage from a multimeter by connecting various series resistances in the circuit through a range selection switch. By adjusting the value of the resistance we get the required D.C. voltage.
7. Multimeter can be used only for low resistance measurement.
a) True
b) False
Answer: b
Explanation: A multimeter is used for the measurement of A.C. as well as D.C. voltage, current and resistance. By manipulating the scale with a multiplication factor of 100 and 10, 000 we can make use of a multimeter for measuring high resistances.
8. What is the role of a rectifier in a multimeter?
a) bias purpose
b) thermal stability
c) rectification
d) inversion
Answer: c
Explanation: When the multimeter is used for the measurement of A.C. voltages, rectifier section is used. It mainly performs the conversion of the input A.C. voltage into D.C. for the measurement of A.C. voltage.
9. What is the initial setting made in a multimeter before it is used for measuring resistance?
a) fine adjustment
b) instrument is open circuited
c) voltage is applied
d) zero adjustment
Answer: d
Explanation: Initially the multimeter is short circuited and zero adjustment control is made. This is done till the meter reads zero resistance or in other words displays full scale current.
Digital Voltmeters
1. Digital voltmeters converts ________
a) analog to digital signal
b) digital to analog signal
c) current to voltage
d) resistance to voltage
Answer: a
Explanation: In general digital voltmeters are known as DVM. They convert analog signals into digital voltage. They also display the voltage to be measured in the form of discrete numerals in place of pointer deflection.
2. Digital voltmeters can be used to measure ________
a) voltage only
b) voltage, temperature, pressure, etc
c) voltage and current
d) voltage and resistance
Answer: b
Explanation: Digital voltmeters are used for the measurement of A.C. as well as D.C. voltages and also to measure physical quantities such as temperature, pressure, stress etc. through the use of appropriate transducer and signal conditioning circuits.
3. A digital voltmeter reduces parallax error.
a) True
b) False
Answer: a
Explanation: A digital voltmeter minimizes the errors due to human interference, interpolation mismatch and errors due to parallax. A digital display is used to show the output voltage on a front panel.
4. In a DVM, a transducer converts ________
a) input to a proportional current
b) input to a proportional power
c) input to a proportional voltage
d) input to a proportional resistance
Answer: c
Explanation: In a digital voltmeter, a transducer is used. In general a transducer converts a physical quantity into an electrical signal. In a DVM the transducer converts the input signal into a proportional voltage.
5. In a DVM, a signal conditioning circuit is used ________
a) to bring current to a suitable limit
b) to bring resistance to a suitable limit
c) to bring resistance to s suitable limit
d) to bring voltage to a suitable limit
Answer: d
Explanation: In a DVM, signal conditioning circuit is used. It converts the input signal into an voltage of suitable limit. This is done so that the voltmeter can read the magnitude of the signal correctly.
6. Input range of DVM is _________
a) 1 V to 1000 V
b) 0.1 V to 10 V
c) 0.01 V to 1 V
d) 0.001 V to 0.1 V
Answer: a
Explanation: In a DVM, the input voltage range is given as 1 V to 1000 V. It includes automatic range selection and overload indication.
7. Output in digital form can’t be used directly.
a) True
b) False
Answer: b
Explanation: The output obtained from a DVM can be used directly. It can be recorded and is also suitable for further processing.
8. What is the effect of IC chips on DVM?
a) increase in cost
b) increase in power
c) reduction in cost
d) increase in size
Answer: c
Explanation: Advancement in IC chips have ensured the reduction in the cost of the DVM’s. Size and power needs of DVM’s have been reduced by a huge margin.
Performance Parameters of Digital Voltmeters
1. Basic range of DVM is _________
a) 1 or 10 V
b) 0.1 or 1 V
c) 10 or 100 V
d) 100 or 1000 V
Answer: a
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.
2. Accuracy of a DVM is ________
a) low
b) high
c) medium
d) zero
Answer: b
Explanation: 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.
3. Input impedance of a DVM is ________
a) low
b) zero
c) high
d) medium
Answer: c
Explanation: 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.
4. In DVM the common mode rejection noise is eliminated by ________
a) increasing the signal amplitude
b) making use of a resistance
c) using a transformer
d) guarding
Answer: d
Explanation: In a DVM, common mode noise can be eliminated through guarding. A guard is basically a sheet metal box around the circuit. This is made available to the circuit being measured by making use of a terminal at the front panel.
5. Output of DVM needs ________
a) 4 lines
b) 2 lines
c) 8 lines
d) 16 lines
Answer: a
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.
6. Normal mode noise can be eliminated through ________
a) attenuation
b) filtering
c) amplification
d) a transformer
Answer: b
Explanation: 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.
7. DVM has ________
a) 1-3 digits
b) 2-5 digits
c) 3-6 digits
d) 7-10 digits
Answer: c
Explanation: 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.
8. What is a digitizing circuit?
a) converts digital signal to analog
b) boosts the magnitude of a digital signal
c) attenuates a digital signal
d) converts analog signal to digital
Answer: d
Explanation: 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.
9. User must wait for a stable reading.
a) True
b) False
Answer: a
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.
Successive Approximation Type DVM
1. A successive approximation type DVM makes use _______
a) of a digital divider
b) of an analog divider
c) of an oscillator
d) of a transducer
Answer: a
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.
2. Successive approximation type DVM is based on the principle of ______
a) acceleration of an object
b) weight of an object
c) velocity of an object
d) momentum of an object
Answer: b
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.
3. Which compares the output in a successive approximation type DVM?
a) op amp
b) diode
c) comparator
d) rectifier
Answer: c
Explanation: A comparator is used to compare the output of the digital to analog converter in a successive approximation type DVM. As a result the comparator provides high or low signals.
4. D/A converter generates the set pattern successively.
a) True
b) False
Answer: a
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.
5. What is the role of logic control and sequencer in a successive approximation type DVM?
a) generate analog voltage
b) generate power
c) generate current through resistance
d) generate sequence code
Answer: d
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.
6. Resolution of a successive approximation type DVM is given by which of the following relation?
a) R = 1⁄10n
b) R = 1⁄10
c) R =10n
d) R = 10
Answer: a
Explanation: The resolution of a successive approximation type depends on the number of digits. It is given by the relation,
R = 1⁄10n
where, R is the resolution
n is the number of digits.
7. Sensitivity of a successive approximation type DVM is given by which of the following relation?
a) S = fsmin
b) S = fsmin × R
c) S = R
d) S = fsmin ⁄ R
Answer: b
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.
8. Speed of a successive approximation type DVM can be improved by making use of ______
a) electrical switches
b) mechanical devices
c) solid state devices
d) transformers
Answer: c
Explanation: 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.
9. Accuracy depends on external supply.
a) True
b) False
Answer: b
Explanation: 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.
Ramp Type DVM
1. Ramp type DVM uses ___________
a) a linear ramp technique
b) a non-linear ramp technique
c) an exponential ramp technique
d) an asymptotic ramp technique
Answer: a
Explanation: A ramp type DVM makes use of a staircase ramp technique or a linear ramp technique. Compared to the linear ramp technique, the staircase ramp technique is much simpler.
2. Linear ramp technique is based on __________
a) voltage measurement
b) time measurement
c) current measurement
d) resistance measurement
Answer: b
Explanation: 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.
3. Time is measured using __________
a) clock
b) logic gates
c) counter
d) flip-flops
Answer: c
Explanation: An electronic counter is used for the measurement of time in the linear ramp technique. A digital display is used to show the numerical value of time.
4. Which is the main device used in the linear ramp technique?
a) exponential ramp
b) asymptotic ramp
c) non-linear ramp
d) linear ramp
Answer: d
Explanation: 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.
5. Resolution depends on __________
a) frequency
b) resistance
c) voltage
d) current
Answer: a
Explanation: 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.
6. How is input voltage measured?
a) by using a voltmeter
b) by counting the pulses
c) by using a multimeter
d) by using a transformer
Answer: b
Explanation: 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.
7. Which determines the rate of measurement cycles?
a) oscillator
b) amplifier
c) mutivibrator
d) oscilloscope
Answer: c
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.
8. What is the typical value of the multivibrator?
a) 10 cycles/second
b) 0.2 cycles/second
c) 50 cycles/second
d) 5 cycles/second
Answer: d
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.
9. Swing of the ramp is __________
a) ±12 V
b) ±10 V
c) ±8 V
d) ±5 V
Answer: a
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.