Temp Sensor
Thermocouple output
Small voltage created by Seeback effect
Which device has the lowest permanent pressure loss: orifice plate, rotameter, or Venturi?
Venturi meter.
What does GF stand for?
Gauge Factor.
Why use a piezoelectric accelerometer?
It converts vibration into charge/voltage with high frequency response.
State Ohm’s Law.
V = IR.
Why does a thermocouple require Cold Junction Compensation (CJC)?
because it measures temperature difference, not absolute temperature
Define beta ratio (β).
The ratio of throat diameter to pipe diameter: β = d₂ / D₁.
Why use a half-bridge for bending?
One gauge is in tension and one in compression → signals add, temperature cancels.
Define resonant frequency.
The natural frequency at which the sensor vibrates and its output becomes distorted.
Write the voltage divider equation.
Vout=Vin(R2/R1+R2)
An RTD is made from which material and outputs what type of signal?
Platinum; resistance that increases with temperature.
Write the Venturi meter flow equation.
Q=CdA2 square root 2 delta P/rho(1-beta4)
Calculate strain using GF and ΔR/R.
E =
E=(delta R/R)/GF
Why must the measurement frequency be far below the resonant frequency?
To ensure accurate, linear response without amplification or distortion.
How does a multimeter measure resistance?
It applies a known current and measures the voltage drop.
Explain the Law of Intermediate Temperatures in one sentence.
The thermocouple voltage between two temperatures equals the sum of voltages across intermediate temperature steps.
Why does an orifice plate waste more energy than a Venturi?
Sharp edges cause large permanent pressure loss due to flow separation.
Why is a Wheatstone bridge needed for strain measurement?
Because strain gauges create tiny resistance changes that must be amplified into voltage.
What electrical problem occurs when two grounds exist (machine chassis + DAQ wall outlet)?
A ground loop.
Why does a Wheatstone bridge improve the ability to detect very small resistance changes compared to measuring resistance directly with a multimeter?
A Wheatstone bridge converts tiny resistance changes into measurable voltage differences and cancels out large fixed resistances, allowing the circuit to amplify only the small change of interest—something a multimeter cannot resolve accurately.
Thermocouples, RTDs, and thermistors all respond to temperature, but each does so using a different physical principle.
Explain the sensing principle of all three sensors in one sentence each.
Thermocouple: Generates a voltage from the Seebeck effect between two dissimilar metals.
RTD: Changes resistance because metals increase resistance with temperature.
Thermistor: Shows a large change in resistance due to temperature-dependent charge carrier movement in semiconductors.
Explain why a Venturi meter has significantly lower permanent pressure loss than an orifice plate, focusing only on fluid dynamics concepts
Because a Venturi has smooth, gradual converging and diverging sections that minimize turbulence and flow separation, while an orifice plate causes sudden contraction and separation that wastes energy as irreversible pressure loss.
Why does installing strain gauges in a full-bridge configuration greatly improve both sensitivity and temperature compensation compared to a quarter-bridge?
A full bridge improves sensitivity because all four gauges change in complementary ways that add to the output, and it improves temperature compensation because all gauges experience the same thermal drift, which cancels out in the bridge.
Explain why accelerometer mounting method (stud, adhesive, magnet, handheld probe) dramatically changes the accuracy of high-frequency vibration measurements.
High-frequency vibrations require a rigid mechanical path; any flexible or compliant mounting (like magnets or adhesives) adds resonance and damping that distort the transmitted vibration and produce false frequency content.
Describe why resistance cannot be measured directly when a component is operating inside a powered circuit (such as a thermistor or strain gauge).
Because the circuit’s voltage and current interfere with the meter’s test signal, making the reading meaningless—resistance must be measured indirectly by converting it into a voltage using a divider or bridge when the circuit is energized.