Sensors, bridges, data acquisition and feedback control. Short problems, quick points.
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Accuracy is how close a measurement is to the true value; precision is how repeatable it is.
A gauge reads 10.0, 10.1 and 9.9 when the true value is 12.0. The gauge is:
Tightly grouped but far from the true value: precise, not accurate.
MeasurementuncertaintyaccuracyRTDstrain gaugeThat was 1 of 3 problems in this section. The full course has the lesson, a worked example and every problem. Try all of it free for 3 days →
A Wheatstone bridge is balanced (zero output) when the resistance ratios on both sides match, R1/R2 = R3/R4, which lets you find an unknown resistor.
A quarter-bridge strain gauge (GF = 2) with 10 V excitation sees 500 μɛ. What is the bridge output?
Vo ≈ Vex(GF)(ε)/4 = 10(2)(0.0005)/4 = 2.5 mV.
Wheatstone Bridgeanalog-to-digitalresolutionThat was 1 of 3 problems in this section. The full course has the lesson, a worked example and every problem. Try all of it free for 3 days →
Blocks in series multiply; blocks in parallel add.
Blocks of 2 and 5/(s + 1) are in series. What is the overall transfer function?
Series blocks multiply: 10/(s + 1).
Common trap: (D) adds them, which is the rule for parallel blocks.
Control Systemsblock diagramtransfer functionsteady-state errorThat was 1 of 3 problems in this section. The full course has the lesson, a worked example and every problem. Try all of it free for 3 days →
A standard second-order system ωn2/(s2 + 2ζωns + ωn2) overshoots by e−πζ/√(1−ζ²) and settles (2% band) in about 4/(ζωn).
A system has poles at s = −2 and s = +1. It is:
A pole with a positive real part grows without bound: unstable.
second-order systempercent overshootsettling timestabilityThat was 1 of 3 problems in this section. The full course has the lesson, a worked example and every problem. Try all of it free for 3 days →
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