WHEATSTONE BRIDGE惠斯通电桥实验报告

No. Date:2020.5.6 Student number: Name:

1

Title:WHEATSTONE BRIDGE

【Aim 】

To determine the resistance of a wire specimen using a Wheatstonebridge.

【Theory 】

known to high precision, then R x can be measured to high precision. Very small changes in R x disrupt the balance and

are readily detected.

When the bridge is balanced, that is V BD =0, thus

1122I R I R =, 102x I R I R = (1)

So we can get that

1122

102x

I R I R I R I R = (2)

That is

12

0x

R R R R = (3)

So 2

01

x

R R R R =

(4) In fact, it is difficult to exactly decide the value of 2

1/R R , so we use "exchange measure method" to obtain R x .

Exchange the positions of R 1and R 2, or R 0and R x , and adjust R 0to a new value 0

′R , the bridge can get a new

balanced state, thus

102

x R R R R '

=

(5)

Combine equation (4) and (5), we can get

x R = (6)

This equation has nothing to do with R 1and R 2. In this way, we can make the error only relate to the instrument error of R 0, which is the instrument error of the resistor box.

%α⋅=∆x Rx R =885.3╳0.1%=0.9 (Ω)

x

x x R R R =±∆=885.3±0.9(Ω)

S =64.3

【Conclusions 】