Analog Multimeter MeasuringCurrent 10-26
Transcript of Analog Multimeter MeasuringCurrent 10-26
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Analog Multimeter, MeasuringCurrent
Steps in using your meter to
measure Current flow.
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Basic Steps and Precautions
Remember; Voltage is measured across
a component, but current flowsthrough a component.
You must break the circuit and place
the meter in series with the circuitand/or component.
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This is not a Auto-ranging DigitalMultimeter! Pay attention to the
polarity of the circuit components and
the lead placement.
The Black Lead is the Negative Lead.
The Red Lead is the Positive Lead.
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This is the circuit without the meter
leads in place
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Can you calculate the total resistance?
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Try the following steps to calculate RT
Take R1 or R5 value and divide by 2
This gives you 4.7k /2 = 2350
Now bring R2 in to the mix
2
2
equiv
ParallelEquiv
equiv
R xRR
R R
2350 101902.83
2350 10
x k
k
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Add Equivalent value to R3 and R4
RT = R1,5,2 equiv + R3 + R4
RT
= 1902.83 + 240 + 470k
RT = approximately 472.143k
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IT can now be calculated
You have calculated RT = 472.143K
The total voltage is given as 12VDC.T
T
T
EI
R
1225.416
472.143A
k
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You must break the circuit to place the
meter in series with the component.
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Remember to start at a higher level
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You calculated less than 50A
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You would use the 50 meter range and
this would be the actual range
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This means 20 = 20, 40 = 40 etc
The minor increments = 1.0 A
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What is the meter reading?
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This meter reading is approximately
25.4A. Can you see it?
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Do you know if any other points will have
the same value? If so, where and why?
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Places to measure IT with probes placed
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Calculations for Parallel branches
Calculate voltage drop for parallel
equivalent circuit
Use the calculated equivalent resistance
for the parallel branches multiplied by
the total current.
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254.16 x 1902.83 48.36mV
The next step is to divide the
equivalent voltage by each branchs
resistance to determine thatbranchs current.
The sum of the Branch currents
should equal the Total Currentapplied.
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Here are the component values again
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Remember; the voltage is .04836 V.
.04836 / 10000 = 4.836A
Two resistances of 4.7k
.04836 / 4700 10.29A
IT 25.416A
4.836 + 10.29 + 10.29 = 25.416A
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Where would you open the Parallel
circuits to measure the currents?
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Here is where you open the Parallel
circuits to measure the currents?
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Where would you place your probes to
measure the calculated currents?
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You calculated less than 50A
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You would use the 50 meter range and
this would be the actual range
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This means 20 = 20, 40 = 40 etc
The minor increments = 1.0 A
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What is the meter reading?
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This meter reading is approximately
4.8A. Can you see it?
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You would use the 50 meter range and
this would be the actual range
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What is the meter reading?
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This meter reading is approximately
10.3A. Can you see it?
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Questions?
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The End
Developed and Produced by the
Instructors in the CIE InstructionDepartment. 10/2011