_V1 20V R1 w 400ΚΩ R2 400ΚΩ
Given the circuit below. The voltage across R2 is measured with the following meters:
- Analog voltmeter ( Rin = 100KΩ )
- An oscilloscope ( Rin = 1MΩ )
- A DMM ( Rin = 10MΩ )
Determine:
The theoretical voltage across R2
VR2 = (400kΩ / (400kΩ + 400kΩ)) * 20V = 10V
The actual voltage measured by the analog meter and the % error
Req = R2 || Rin → ( (400kΩ * 100kΩ) / (400kΩ + 100kΩ) ) → Req = 80kΩ
Vreq = ((80kΩ) / (400kΩ + 80kΩ)) * 20V = 3.33V
The actual voltage measured by the analog meter is 3.33V
% error = ((3.33V - 10V) / 10V) * 100 → % error = 66.7%
The actual voltage measured by the oscilloscope and the % error
Req = R2 || Rin → ( (400kΩ * 1MkΩ) / (400kΩ + 1MΩ) ) → Req = 285.7kΩ
Vreq = ((285.7kΩ) / (400kΩ + 285.7kΩ)) * 20V = 8.33V
The actual voltage measured by the oscilloscope is 8.33V
% error = ((8.33V - 10V) / 10V) * 100 → % error = 16.7%
The actual voltage measured by the DMM and the % error
Req = R2 || Rin → ( (400kΩ * 10MkΩ) / (400kΩ + 10MΩ) ) → Req = 384.6kΩ
Vreq = ((384.6kΩ / (400kΩ + 384.6kΩ)) * 20V = 9.8V
The actual voltage measured by the oscilloscope is 9.8V
% error = ((9.8V - 10V) / 10V) * 100 → % error = 2%
Can you check if my answer is correct?
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