Undergrad Measuring Low Resistance: Why Meter Bridge is the Preferred Choice

Click For Summary
The meter bridge is preferred over the post office box for measuring low resistance due to its superior sensitivity and accuracy. The post office box, which operates as a Wheatstone bridge, is limited in its measurement range and primarily used for identifying short circuits rather than measuring resistance. Its design does not effectively utilize the meter's sensitivity because it is affected by the bridge components. Additionally, the meter bridge allows for a more precise measurement technique by enabling current to pass through the meter for full-scale deflection before measuring the voltage drop across an unknown low resistance. Overall, the meter bridge is more effective for low resistance measurements compared to the post office box.
phymath7
Messages
48
Reaction score
4
TL;DR
Why post office box can't be used to measure high or low resistance?
Why meter bridge is chosen over post office box to measure low resistance?
 
Physics news on Phys.org
What is "post office box" (or "vox")?
 
Ah. According to the Wikipedia article the Post Office Box (origin UK) is in fact a Wheatstone bridge circuit.
 
phymath7 said:
TL;DR Summary: Why post office box can't be used to measure high or low resistance?

Why meter bridge is chosen over post office box to measure low resistance?
Who says it can't be used to measure high or low resistance ?
The post office box was two arms of a Wheatstone bridge.
It was used to find short circuits, not open breaks in the line.
 
phymath7 said:
TL;DR Summary: Why post office box can't be used to measure high or low resistance?

Why meter bridge is chosen over post office box to measure low resistance?
I think the measurement range will be limited by the available ratio arms and standard resistances. In addition, a bridge does not make best use of the meter sensitivity because it is shunted by the bridge components. There is a sensitive method for low resistances where we first pass a current through the meter to give full scale deflection and then measure the drop in reading when the meter is shunted by the unknown low resistance.
(Sorry, I recently disposed of my copy of "Telephony", by Herbert and Proctor, which would have given the definitive answer).
 

Thread 'Reference frames, center of rotation, etc'

Topic about reference frames, center of rotation, postion of origin etc Comoving ref. frame is frame that is attached to moving object, does that mean, in that frame translation and rotation of object is zero, because origin and axes(x,y,z) are fixed to object? Is it same if you place origin of frame at object center of mass or at object tail? What type of comoving frame exist? What is lab frame? If we talk about center of rotation do we always need to specified from what frame we observe?
View full post »

Similar threads

Measurement technology textbook problems
  • · Replies 1 ·
Replies
1
Views
717
Undergrad How to understand experiment to measure heat capacity of solid?
  • · Replies 1 ·
Replies
1
Views
2K
Measurement technology textbook problems
  • · Replies 2 ·
Replies
2
Views
619
Undergrad Why does resistance reduce current in whole circuit?
  • · Replies 38 ·
2
Replies
38
Views
5K
Meter Bridge Experiment: Limitations for Measuring Small Resistance
  • · Replies 8 ·
Replies
8
Views
8K
Calculating Copper Wire Gauge for Resistance Thermometer Bridge Circuit
  • · Replies 6 ·
Replies
6
Views
2K
Human Resistance vs. Circuit Conductors
  • · Replies 6 ·
Replies
6
Views
1K
Wheatstone bridge, only one R value known
  • · Replies 30 ·
2
Replies
30
Views
3K
Trying to buy a quality EM meter for low frequency measurements
  • · Replies 4 ·
Replies
4
Views
2K
Theoretical vs measured electrical resistance: Percent error relation
  • · Replies 9 ·
Replies
9
Views
6K