1 Government Polytechnic, Muzaffarpur ELECTRONIC MEASUREMENTANDINSTRUMENTATION LAB Subject Code: 1621308 Experiment 1 Aim: Conversion of Galvanometer into Ammeter and Voltmeter. Materials required: Galvanometer Cell Rheostat Ammeter of desired range Resistance wire Key Screw gauge Lab Procedure: The shunt resistance required to convert the galvanometer into ammeter of range I is calculated using the formula, G-the resistance of the galvanometer. I- the range of desired ammeter Ig = nk, the current required for full scale deflection in the galvanometer, where, n- total number of divisions in the galvanometer k- the figure of merit of the galvanometer. Then, the length of the wire required for shunt can be calculated using the formula,
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Government Polytechnic, Muzaffarpur
ELECTRONIC MEASUREMENTANDINSTRUMENTATION LAB
Subject Code: 1621308
Experiment 1
Aim: Conversion of Galvanometer into Ammeter and Voltmeter.
Materials required:
Galvanometer
Cell
Rheostat
Ammeter of desired range
Resistance wire
Key
Screw gauge
Lab Procedure:
The shunt resistance required to convert the galvanometer into ammeter of range I is
calculated using the formula,
G-the resistance of the galvanometer.
I- the range of desired ammeter
Ig = nk, the current required for full scale deflection in the galvanometer,
where, n- total number of divisions in the galvanometer
k- the figure of merit of the galvanometer.
Then, the length of the wire required for shunt can be calculated using the formula,
2
Where, ρ- the resistivity of material of the wire
r- the radius of the wire, which can be measured using a screw gauge.
Cut the resistance wire at a length of (l+2) cm.
Make two marks near the ends of the wire so that the distance between the marks is
exactly l cm.
The wire is now connected to the terminals of the galvanometer so that the marks are just
outside the terminals of the galvanometer.
The galvanometer with the shunt connected across its terminals is the converted ammeter
of the desired range.
Connections are made as shown in the circuit diagram.
The galvanometer with shunt resistance is connected in series to a battery through an ammeter, key
and rheostat.
Insert the key.
Adjust the rheostat and set the current reading I of the given ammeter at a particular value.
The reading of the galvanometer Ig’ is noted. Now, the current through the converted ammeter is
calculated using the relation,
The error of the converted ammeter is calculated as I – I’.
Repeat the experiment by changing the rheostat resistance.
A graph can be drawn with (I – I’) along Y-axis and I’ along X-axis. This is called the
correction graph.
Thus, the converted ammeter is verified with an ammeter of the same range and a
correction graph is obtained.
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Observations:
Resistance of the galvanometer, G = ............ohms
Figure of merit of the galvanometer, k = ............... amp./div.
Number of divisions in the galvanometer scale, n = ................
Current for full scale deflection, Ig = nk =............amp.
Desired range of the converted ammeter (I) ---------mA
Shunt resistance,
Calculations:
Shunt resistance,
Radius of the wire, r = --------cm = ------- X 10-2 m.
Resistivity of the material of the wire, ρ = --------------Ωm
Length of the wire required for shunt can be calculated using the formula,
Result:The given galvanometer is converted into an ammeter of range 0 to ………….A by
connecting a shunt resistance of …………ohms
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Government Polytechnic, Muzaffarpur
ELECTRONIC MEASUREMENTAND INSTRUMENTATION
LAB
Subject Code: 1621308
Experiment 2
Calibration of Ammeter, Voltmeter and Wattmeter.
Objective:
Calibration of voltmeter using DC potentiometer
Calibration of Ammeter using DC potentiometer
Apparatus Required:
1. Calibration of voltmeters and ammeter by Potentiometer
2. Potentiometer
3. Sliding jockey
4. Mains cord
5. Patch cords
Theory:
A potentiometer instrument for measuring the potential (or voltage) in a circuit taps off a fraction
of a known voltage from a resistive slide wire and compares it with the unknown voltage by
means of a galvanometer. The potentiometer method is the usual basis for the calibration of
voltmeters, ammeters, and wattmeters. Since the potentiometer is a DC measurement device, the
instrument to be calibrated must be of the DC or electrodynamometer type. One of the first
requirements in this calibration procedure is that a suitable, stable DC supply be available, since
any variation in the supply voltage causes a corresponding change in the voltmeter calibration
voltage.
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Diagram of Callibration of Voltmeter:
Diagram of Callibration of Ammeter:
Procedure:
1. Connect the mains cord to the Trainer kit and switch On Mains Supply.
3. Note the output of standard DC supply (Vdc) by connecting terminal 32 to digital voltmeter
V1’s positive terminal and ground terminal 6 to negative of V1.
4. Once voltage is noted from V1, disconnect them and connect the negative terminal of
galvanometer G1 to positive terminal 32 of DC supply.
5. Connect positive terminal of G1 to jokey.
6. Connect terminal 3 and 4 to digital ammeter A1 polarity wise.
7. Connect DC potentiometer between terminal 5 and 6. Connect 5 to X and 6 to Z terminal. 8.
Vary VR2 knob to set the current in A1 (say 30 mA).
9. Touch jokey to X and then to Z terminals of potentiometer and see the reading of
galvanometer. Compare both reading of galvanometer.
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10. Now slide the jokey on potentiometer wire and the find null point i.e., the point where
galvanometer G1 shows zero reading.
11Connect the circuit according to the provided circuit Diagram.
12. Set the voltage in analog DC Voltmeter (V) to some value (say 1 V) with the help of VR1
knob.
13. Touch jokey to X and then to Z terminals of potentiometer and see the reading of
galvanometer. Compare both reading of galvanometer.
14. Now slide the jokey on potentiometer wire and the find null point.
15. Now measure distance D (in cm) moved from terminal Z to null point.
Observation Table:
For Voltmeter Calibration
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For Ammeter Calibration
Distance L (in cm) moved from terminal Z to null point is
L = [(n-1)*100 + r] cm.
n= number of wire from the Z terminal, for odd line of wire take reading from lower scale and
for even line wire take reading from upper scale.
C=Vdc /L VDC = DC Supply Voltage.
L= Distance
C= Voltage drop per cm.
Precaution:
1. Handle all the equipments with care
2. Make connections according to circuit diagram
3. Take the readings carefully& the connections should be tight
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Government Polytechnic, Muzaffarpur
ELECTRONIC MEASUREMENTANDINSTRUMENTATION
LAB
Subject Code: 1621308
Experiment 3
Determination of Inductance, Capacitance using AC bridges.
Object:- Measurement of the unknown inductance by using Hay’s bridge method
A ferrite "bead" choke, consisting of a cylinder of ferrite encircling a computer power cord to
block electronic noise.
Common-mode (CM) chokes:
The common-mode choke, where two coils are wound on a single core, is useful for suppression
of electromagnetic interference (EMI) and radio frequency interference (RFI) from power supply lines and for
prevention of malfunctioning of power electronics device. It passes differential currents (equal but opposite),
while blocking common-mode currents.[2] The magnetic flux produced by differential-mode (DM) currents in the
core tend to cancel each other out since the windings are negative coupled. Thus, the choke presents little
inductance or impedance to DM currents. Normally this also means that the core will not saturate for large DM
currents and the maximum current rating is instead determined by the heating effect of the winding resistance.
The CM currents, however, see a high impedance due to the combined inductance of the positive coupled
windings.
A typical common-mode choke configuration. The common mode currents, I1 and I2, flowing in the
same direction through each of the choke windings, creates equal and in-phase magnetic fields
which add together. This results in the choke presenting a high impedance to the common mode
signal
Near magnetic field emission reduction
When the CM choke is conducting CM current, most of the magnetic flux generated by the windings is confined with the inductor core due to its high permeability. In this case, the leakage flux, which is also the near magnetic field emission of the CM choke is low. However, the DM current flowing through the windings will generate high emitted near magnetic field since the windings are negative coupled in this case. To reduce the near magnetic field emission, a twisted winding structure can be applied to the CM choke.
The prototype of the balanced twisted winding CM choke
CM choke with DM current
The difference between the balanced twisted windings CM choke and conventional balanced two winding CM choke is that the windings interact in the center of the core open window. When it is conducting CM current, the balanced twisted winding CM inductor can provide identical CM inductance as the conventional CM inductor. When it is conducting DM current, the equivalent current loops will generate inversed direction magnetic fields in space so that they tend to cancel each other.
The equivalent current loops and the magnetic fields generated
Measurement for near magnetic field emission
We need to conduct a current to a certain inductor. And then, use a probe to measure the near field emission. First of all, a signal generator is connected to an amplifier, serving as a voltage source. The output of the amplifier is then connected to the measured inductor. To monitor and control the current flowing through the inductor, a current clamp is used to clamp the conducting wire. An oscilloscope is connected to the current clamp to show the current waveform. A probe is then used to measure the flux in the air. A spectrum analyzer is connected to it to collect the data
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Government Polytechnic, Muzaffarpur
ELECTRONIC MEASUREMENTANDINSTRUMENTATION LAB
Subject Code: 1621308
Experiment :5
Aim: To observe the loading effect of a multi-meter while measuring voltage across a low
1.9 Refer to Figure 4. Calculate the voltage across each of the resistors using the voltage
divider rule.
V1(unloaded)
V2(loaded)
1.10 Connect the circuit of Figure 4 and measure the voltages V1 and V2 with both the
DMM and VOM voltmeters.
Reading V1 V2
DMM
VOM
1.11 Calculate the corresponding loading effect of the DMM and the VOM
1.12 Replace the resistors 5.6 kW and 3.9 kW with 5.6 MW and 3.9 MW in Figure 4.
Calculate the voltage across each of the resistors and measure the voltage across each of
the resistors with DMM and VOM.
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1.13 Calculate the corresponding loading effect of the DMM and the VOM.
3. Ammeter Loading Effect:
Use a DMM ohmmeter to measure the actual resistance of a 4.7 W resistor. Use a
DMM voltmeter to adjust the voltage source to 0.3 V. Calculate the unloaded current of
the circuit in Figure 5.
Actual resistance of the 4.7 W
resistor = ____________W
Unloaded current , I = _______________A
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Connect the circuit of Figure 5. Use the DMM as ammeter first and record the meter’s
reading. Repeat with a VOM ammeter. (Ensure that the ammeter is on the correct range
and polarity to measure the current).
Calculate the loading effect of the two ammeters
2.4 Calculate the internal resistance of each of the ammeters
2.5 Replace the 4.7 W resistor with a 47 W resistor and adjust the voltage of the DC supply to
3 V. Measure the current of the circuit with the DMM and VOM ammeters and
calculate the corresponding loading effect.
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Government Polytechnic, Muzaffarpur
ELECTRONIC MEASUREMENTANDINSTRUMENTATION LAB
Subject Code: 1621308
Experiment :6
Aim:Measurement of voltage, frequency, time period and phase angle using Cathode Ray
Oscilloscope (CRO).
Apparatus: CRO, Function generator, Digital Voltmeter, Connecting Wires
Circuit Diagram:
An oscilloscope is a measuring device used commonly for measurement of voltage, current, frequency, phase difference and time intervals. The heart of the oscilloscope is the cathode ray tube, which generates the electron beam, accelerates the beam to high velocity, deflects the beam to create the image, and contains the phosphor screen where the electron beam eventually becomes visible. To accomplish these tasks, various electrical signals and voltages are required. The power supply block provides the voltages required by the cathode ray tube to generate and accelerate the electron beam, as well as to supply the required operating voltages for the other circuits of the oscilloscope. Relatively high voltages are required by the cathode tubes, on the order of a few thousand volts, for acceleration, as well as a low voltage for the heater of the electron gun, which emits the electrons. Supply voltages for the other circuits are various values usually not more than few hundred volts.
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The oscilloscope has a time base, which generates the correct voltage to supply the cathode ray tube to deflect this part at a constant time dependent rate. The signal to be view is fed to you vertical amplifier, which increases the potential of the input signal to a level that will provide a usable deflection of the electron beam. To synchronize the that the horizontal deflection starts at the same point of the input vertical signal each time it sweeps, a synchronizing or triggering circuit is used. This circuit is the link between the vertical input and the horizontal time base. Procedure: Phase Measurement using Lissajous Patterns (X-Y Mode):
To Measure the phase difference of two sine waves their frequencies must be equal.
1. Connect a 1Volt peak-peak, 1KHz sine wave signal from the function generator to the
horizontal input of the CRO.
2. Connect the output of phase shift network to the vertical input as shown in figure.
3. Adjust the vertical and horizontal gains properly for good display.
4. Observe Lissajous Patterns for different combinations of R and C values.
Calculate the phase angle as
Sine θ = A/B
A: Distance between the points where the ellipse crosses the y-axis and the origin. B: Distance between the origin and the y – co-ordinate of the maxima of the ellipse. Calculate theoretical phase difference as
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! = tan-1 (f1/f2)
Where f2 = 1/2"RC f1 = input signal frequency.
LISSAJOUS’ FIGURES
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Government Polytechnic, Muzaffarpur
ELECTRONIC MEASUREMENTANDINSTRUMENTATION LAB
Subject Code: 1621308
Experiment :7
Aim: Measurement of time period, frequency,
Theory:
There are many methods for measurements of frequency or time. In our experiment only a few of
them are used: analog methods based on measurement of time with the oscilloscope, and direct
method based on of measurement frequency and time with the multifunction digital counter.
Oscilloscope method used in the experiments are extremely simple - they implement either
internal (linear) time base, or external reference signal (Lissajous method). Having known the
time base speed time/div (a value which may be read from oscilloscope’s screen), all we need to
do is to measure the length of one or more cycles of the observed signal.. This method is fast but
not very precise.
Sinusoidal (external) time-base method (The Lissajous method).
An other analog frequency measurement method involving the oscilloscope rely on using the
oscilloscope as a kind of null indicator for comparison of a sine signal with unknown frequency
with a reference sine signal whose frequency should be well defined and easily varied. One of
the signals is fed to the Y channel of the oscilloscope, the second one to the X channel. An
interaction of these two signals produces on the display more or less complicated snaky loops,
whose form allows for determining the unknown frequency. A typical Lissajous figure is shown
in Fig. 1
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Fig. 1 Frequency measurement with the Lissajous method a) measurement diagram, b) Lissajous
figure and frequency determination.
If we assume that fy is the unknown frequency signal connected to the Y channel and fx is the
reference signal connected to the X channel then we have
where nx, ny denote number of intersections of the Lissajous curve with horizontal and vertical
axes, respectively, and dφ/dt is the rate of phase change (the trace rotation speed). The reference
signal should be adjusted until the displayed figure is possibly stable (dφ/dt ≈ 0). It is sometimes
attainable with difficulty, and needs both signal sources involved having adequate frequency
stability. The method's error is roughly equal to relative calibration error of the reference source.
Due to the mentioned stability problems, usefulness of the method is limited to rather low
frequency applications.
Digital counter method.
Digital counter methods rely on continuing number of events (in this case – the number of
cycles) with the counter open during precisely determined window. The periodic input signal of
any shape, including sine waveform, is formed in an input shaper block to have standard form of
possibly short pulses that are fed to the counter controlled by an accurate and stable quartz
oscillator (see Fig.2).
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If the counter is opened for e.g. 1 second, then the number of pulses counted during this time
directly gives the measured frequency. If we denote open gate time as τ, input signal period as
Tx, and number of cycles counted as N, then
and the unknown frequency is equal to
It is intuitively obvious that the accuracy of this method mainly depends on the accuracy of gate
timing. It may be shown that the limiting error of direct frequency measurement method is equal
to
where δgfref is the limiting error of quartz oscillator frequency.5gfk is the limiting.
In conclusion, one may see that the limiting error of direct frequency measurement method decreases
- as the number N increases, i.e. measured frequency rises,
Table 1. Measurement functions of 53220A Keysight digital frequency counter
Table 2. Measurement functions of 1052 Rigol oscilloscope
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Note: Before the measurements:
- connect power supply to the F01 Module.
- set a frequency counter impedance to 50 Ω for inputs 1 and 2:
Measurements of time parameters of sinusoidal signals
1.1 Use the DFC 53220A (Digital Frequency Counter) to measure time parameters (period and
frequency) of sine signal from generator G1 output in F01 module
Measure appropriate parameters using following functions
a) PERIOD – measure the period of the signal with gating time of 1 s. If selected gating
time is longer than measured period, the DFC measures an average period.
b) FREQ – measure the frequency of the signal with gating time of 1 s. In this case, the
frequency is measured with the indirect method.
c) TOTALIZE:GATED – counting the number of pulses during 1 s of Gate Time. This case
realizes the direct frequency measurement method (using frequency definition – counting of
phenomena occurrences during reference time interval).
Compare and comment obtained results from PERIOD, FREQ and TOTALIZE:GATED
measurement method
1.2 Use the oscilloscope to measure time parameters (period and frequency) of sine signal from
generator G1 output in F01 module.
Take measurements of the period and frequency with the use the manual procedure (length
measurements) and the automatic measurement functions. Set the oscilloscope to minimize
measurements errors.
Insert the oscillograms into the report. Write down Cx constant and measurement results.
Estimate the limiting error of both measurements.
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Compare and comment obtained results of period and frequency measurements with the
corresponding values obtained in point 1.1a and 1.1b. Assume the DFC as a reference
instrument.
Measurements of time parameters of rectangular signals.
2.1 Use the DFC 53220A (Digital Frequency Counter) to measure time parameters (period and
frequency) of sine signal from generator G2 output in F01 module.
Prior to the measurements assess the stability of the G2 generator and adjust the resolution of the
frequency counter. To do this, set the number of digits displayed on the frequency counter
display in a way to achieve observed instability of the result on the least significant digit
.
a) Measure the period and frequency using the PERIOD and FREQ functions respectively. Set
the gating time of 1 s.
Compare and comment on the results
b) Measure the pulse width of rectangular waveform (Width: Pos) and time interval between
pulses (Width: Neg).
c) Determine duty cycle of the signal based on the parameters obtained in point a) and b).
d) Measure the duty cycle of the signal using automatic function in the DFC (DutyCycle: Pos).
Compare and comment results obtained in points c) and d).
2.2 Use the oscilloscope to measure time parameters (period and frequency) of sine signal from
generator G2 output in F01 module
a) Take measurements of the period and frequency with the use the manual procedure (length
measurements) and the automatic measurement functions. Set the oscilloscope to minimize
measurements errors.
Insert the oscillograms into the report. Write down Cx constant and measurement results.
Estimate the limiting error of both measurements
Compare obtained results of period and frequency measurements with the corresponding values
obtained in point 2.1a. Assume the DFC as a reference instrument.
point 3.1.
Compare obtained results of period and frequency measurements with the corresponding values
obtained in point 2.1a. Assume the DFC as a reference instrument.
b) Take measurements of the pulse width and time interval with the use the manual procedure
and the automatic measurement functions (WIDTH+ and WIDTH-).
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Insert the oscillograms into the report. Estimate the limiting error of the measurements.
c) Based on results in point a) and b), determine value of the duty cycle and estimate the limiting
error of both results.
d) Take measurements of the duty cycle with the use of automatic function +DUTY.
Compare values of duty cycle obtained in points 2.1c and 2.1d. Assume the DFC as a reference
instrument
Measurements of phase shift of sinusoidal signals
3.1 Connect the output of the G1 generator to the input of the phase shifter PF in F01 module.
Use the DFC to measure the phase shift between signals on the input and output of the PF
module.
To gain measurement result in range of 0 - 360ºset option:
3.2 Use the oscilloscope to measure phase shift between signals on the input and output of the PF
module. Use the sine signal from G1 as an input signal for the phase shifter (PS).
Take measurements with the use the manual procedure (length measurements. Set the
oscilloscope to minimize measurements errors. Insert the oscillogram into the report and mark all
sectors used for ε calculation.
Estimate the limiting error of phase shift measurement.
Compare and comment obtained result of phase shift measurement with the corresponding value
of phase shift obtained in point 3.1.
Conclusion::
In conclusion, one may see that the limiting error of direct frequency measurement method
decreases
- as the number N increases, i.e. measured frequency rises,
- gating time τ is longer
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Government Polytechnic, Muzaffarpur
ELECTRONIC MEASUREMENTANDINSTRUMENTATION LAB
Subject Code: 1621308
Experiment :8
Aim: Measurement of rise, fall and delay times using a Cathode Ray Oscilloscope
Theory:
Rise Time
In the digital world, rise time measurements are critical. Rise time may be a more appropriate
performance consideration when you expect to measure digital signals, such as pulses and steps.
our oscilloscope must have sufficient rise time to accurately capture the details of rapid
transitions. Rise time describes the useful frequency range of an oscilloscope.
To calculate the oscilloscope rise time required for our signal type, use the following equation:
This basis for oscilloscope rise time selection is similar to that for bandwidth. As in the case of
bandwidth, achieving this rule of thumb may not always be possible given the extreme speeds of
today’s signals. Always remember that an oscilloscope with faster rise time will more accurately
capture the critical details of fast transitions. In some applications, we may know only the rise
time of a signal. A constant allows we to relate the bandwidth and rise time of the oscilloscope,
using the equation:
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Rise time is the amount of time a pulse takes to go from a low to high voltage. By convention,
the rise time is measured from 10% to 90% of the full voltage of the pulse. This eliminates any
irregularities at the pulse’s transition corners. Pulse width is the amount of time the pulse takes to
go from low to high and back to low again. By convention, the pulse width is measured at 50%
of full voltage. Figure 69 illustrates these measurement points.
For rise time and fall time measurements, the 10% and 90% amplitude points are used as starting
and ending reference points.
Procedure:
1. Apply a signal to the INPUT jack. Set the vertical MODE to the channel to be used. Use the VOLTS/DIV and VARIABLE to adjust the waveform peak-to-peak height to five divisions. 2. Using the vertical POSITION control and the other controls, adjust the display sich that the wavedoem is centered vertically in the display. Set the SWEEP TIME/DIV to as fast a setting as possible consistent with observation of both the 10% and 90% points. Set the SWEEP VARIABLE control to CAL position. 3. Use the horizontal POSITION control to adjust the 10% point to coincide with a vertical graduation line and measure the distance in divisions between the 10% and 90% points on the waveform. Multiply this by the SWEEP TIME/DIV and also by 1/10 if "X10MAG" mode was used. . NOTE: The graticule on the CRT includes the 0, 10, 90, and 100 % lines assuming that 5 divisions correspond to 100 %. Use them as a reference for accurate measurements. Using the formula: Risetime = Horizontal distance (div) X (SWEEP TIME/DIV setting) / "X10 MAG" value.
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Example For the example, the horizontal distance is 3.3 divisions. The SWEEP TIME/DIV is 2 (us/div) Substituting the given value Risetime = 3.3 (div) X 2 (us/div) = 6.6 us Rise time and fall time can be measured by making use of the alternate step 3 as described below as well. 4. Use the Horizontal POSITION control to set the 10% point to coincide with the center vertical graduation line and measure the horizontal distance to the point of the intersection of the waveform with the center horizontal line. Let this distance be D1. Next adjust the waveform position such that the 90% point coincides with the vertical centerline and measure the distance from that line to the intersection of the waveform with the horizontal centerline. This distance is D2 and the total horizontal distance is then D1 plus D2 for use in the above relationship in calculating the rise time or fall time. Using the formula: Risetime = (D1 + D2) (div) X (SWEEP TIME/DIV setting) / "X10 MAG" value.
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Example
For the example, the measured D1 is 1.6 divisions while D2 is 1.4 divisions. If SWEEP
TIME/DIV is 2 us/div we use the following relationship
Substituting the given value:
Rise time = (1.6 + 1.4) (div) X 2 (us/div) = 6 us
Conclusion:
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Government Polytechnic, Muzaffarpur
ELECTRONIC MEASUREMENTANDINSTRUMENTATION LAB
Subject Code: 1621308
Experiment :9
Aim: Measurement of R, L and C using a LCR bridge/Universal bridge.
Apparatus Required:
LCR meter ,connecting chords
Theory:
LCR meters are measuring instruments that measure a physical property known as impedance.
Impedance, which is expressed using the quantifier Z, indicates resistance to the flow of an AC
current. It can be calculated from the current I flowing to the measurement target and the voltage
V across the target’s terminals. Since impedance is expressed as a vector on a complex plane,
LCR meters measure not only the ratio of current and voltage RMS values, but also the phase
difference between current and voltage waveforms.
LCR meter measurement circuit: Two-terminal method
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Typical equations for LCR meters
Equivalent circuit mode
Open correction and short correction
The test fixture used when measuring a target has residual components and can be expressed
using an equivalent circuit such as that shown in the figure below. Consequently, the measured
value Zm is expressed using an equation that contains these residual components, as shown
below. To calculate the true value Zx, it is necessary to calculate the open residual component
and short residual component and then correct the measured value. These correction processes
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are known as open correction and short correction, respectively, and LCR meters include
functionality for performing both.
Zm: Measured value
Zs:
Short residual impedance (Rs: residual resistance; Ls: residual inductance)
Yo:
Open residual admittance (Go: residual conductance; Co: stray capacitance)
Zx:
True value (measurement target’s impedance)
Measurement signal level
The measurement signal output from the LCR meter is voltage-divided between the output
impedance R and the measurement target Zx. Thus the set measurement signal level V is not
applied as-is to the measurement target Zx. LCR meters have three measurement signal modes.
Open-voltage (V) mode:
The user sets the measurement signal level V in the figure. This value is the voltage when the
measurement terminals are in the open state.
Constant-voltage (CV) mode:
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The user sets the value Vx in the figure (the voltage between the measurement target Zx’s
terminals). This mode is used when measuring targets that exhibit voltage dependence, for
example MLCCs with a high dielectric constant.
Constant-current (CC) mode:
The user sets the value I in the figure (the current that flows to the measurement target Zx). This
mode is used when measuring measurement targets that exhibit current dependence, for example