Simple
Bridge Name Best for... The Interview Hook
Function
Medium-sized "It's the classic bridge, used everywhere
Wheatstone Measures medium
resistors (the R values from simple resistors to basic fault finding
Bridge resistances.
you see most often). in cables."
"It's the essential upgrade to the
Kelvin's Double Measures Low Very small resistors Wheatstone; it's designed to cancel out the
Bridge resistances. (less than 1 Ω). error from the test leads themselves,
ensuring a perfect reading for low values."
"It's smart because it measures an
Maxwell's Measures Coils with medium unknown L by using a known
Bridge Inductors (L). quality (not too lossy). C—capacitors are cheaper and more stable
standards than inductors."
"This is the power system bridge; its main
Measures
High-voltage job is to measure the insulation quality
Schering Bridge Capacitors (C) and
insulation testing. (loss angle) of big things like cables and
quality.
bushings."
"This bridge is different—it actually
Creating a stable,
Measures measures the frequency of the AC signal
Wien's Bridge single audio
Frequency (f). itself, and it’s the core circuit for many
frequency.
audio oscillators."
Concept DC Bridges AC Bridges Advantages (Applicable to most bridges)
What does it Resistance (R) Impedance (L,C) and High Accuracy: Measurement is based on the null indication
measure? only. Frequency (f). principle (zero current or zero voltage), which does not depend on
Battery (DC AC Oscillator (AC the calibration of the detector itself, leading to very high
Power Source? supply). supply). precision.
More complex, need Independence: The final balance equation is typically independent
special shielding (like of the source voltage and its impedance.
a Wagner Earth Comparison Method: Unknown quantity is accurately compared
Simple, easier to Device) to block stray against a known, precise standard component.
Complexity? use. noise.
Headphones or CRO Disadvantages (General)
Galvanometer (detects AC Sensitivity: The accuracy depends heavily on the sensitivity of the
Detector? (detects DC null). null/silence). null detector (galvanometer for DC, or CRO/Headphone for AC).
Time Consumption: Achieving the exact null balance can be a
time-consuming and tedious manual process.
Heating Effects (DC): In DC bridges measuring low resistance, the
current can cause I2R heating, altering the resistance and
introducing errors.
Shielding (AC): AC bridges are prone to errors from stray magnetic
fields and stray capacitance, necessitating complicated and costly
shielding and earthing arrangements (like the Wagner earth
circuit)
Created By: Zaid Thakor
Bridge Name Best for... The Interview Hook
Function
Medium-sized "It's the classic bridge, used everywhere
Wheatstone Measures medium
resistors (the R values from simple resistors to basic fault finding
Bridge resistances.
you see most often). in cables."
"It's the essential upgrade to the
Kelvin's Double Measures Low Very small resistors Wheatstone; it's designed to cancel out the
Bridge resistances. (less than 1 Ω). error from the test leads themselves,
ensuring a perfect reading for low values."
"It's smart because it measures an
Maxwell's Measures Coils with medium unknown L by using a known
Bridge Inductors (L). quality (not too lossy). C—capacitors are cheaper and more stable
standards than inductors."
"This is the power system bridge; its main
Measures
High-voltage job is to measure the insulation quality
Schering Bridge Capacitors (C) and
insulation testing. (loss angle) of big things like cables and
quality.
bushings."
"This bridge is different—it actually
Creating a stable,
Measures measures the frequency of the AC signal
Wien's Bridge single audio
Frequency (f). itself, and it’s the core circuit for many
frequency.
audio oscillators."
Concept DC Bridges AC Bridges Advantages (Applicable to most bridges)
What does it Resistance (R) Impedance (L,C) and High Accuracy: Measurement is based on the null indication
measure? only. Frequency (f). principle (zero current or zero voltage), which does not depend on
Battery (DC AC Oscillator (AC the calibration of the detector itself, leading to very high
Power Source? supply). supply). precision.
More complex, need Independence: The final balance equation is typically independent
special shielding (like of the source voltage and its impedance.
a Wagner Earth Comparison Method: Unknown quantity is accurately compared
Simple, easier to Device) to block stray against a known, precise standard component.
Complexity? use. noise.
Headphones or CRO Disadvantages (General)
Galvanometer (detects AC Sensitivity: The accuracy depends heavily on the sensitivity of the
Detector? (detects DC null). null/silence). null detector (galvanometer for DC, or CRO/Headphone for AC).
Time Consumption: Achieving the exact null balance can be a
time-consuming and tedious manual process.
Heating Effects (DC): In DC bridges measuring low resistance, the
current can cause I2R heating, altering the resistance and
introducing errors.
Shielding (AC): AC bridges are prone to errors from stray magnetic
fields and stray capacitance, necessitating complicated and costly
shielding and earthing arrangements (like the Wagner earth
circuit)
Created By: Zaid Thakor
