MindMap Gallery Electrical measurement mind map
Mind map of electrical measurement mind map. It includes factors causing temperature errors of strain gauges, temperature compensation methods of resistance strain gauges, resistance strain gauge measurement circuits, etc.
Edited at 2021-10-18 23:06:18One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
Project management is the process of applying specialized knowledge, skills, tools, and methods to project activities so that the project can achieve or exceed the set needs and expectations within the constraints of limited resources. This diagram provides a comprehensive overview of the 8 components of the project management process and can be used as a generic template for direct application.
One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
Project management is the process of applying specialized knowledge, skills, tools, and methods to project activities so that the project can achieve or exceed the set needs and expectations within the constraints of limited resources. This diagram provides a comprehensive overview of the 8 components of the project management process and can be used as a generic template for direct application.
Strain gauge temperature error and compensation
Factors causing temperature errors of strain gauges
Effect of temperature coefficient of resistance wire
Rt=R0(1 αΔt)
ΔRα=Rt-R0=R0αΔt
ΔRα=Rt-R0=R0αΔt
Influence of linear expansion coefficient of specimen material and resistance wire material
The coefficients are the same
Ambient temperature changes will not cause additional deformation
coefficients are different
As the ambient temperature changes, the resistance wire will produce additional deformation, resulting in additional resistance changes.
As the ambient temperature changes, the resistance wire will produce additional deformation, resulting in additional resistance changes.
Calculation formula
length change
ls, lg
The resistance wire is stuck to the component
Δl, εβ, ΔRβ
Relative change in total resistance of strain gauge
ΔRt/R0
other factors
The performance parameters of the strain gauge itself (K0, α, βs) and the linear expansion coefficient βg of the tested piece
Temperature compensation method of resistance strain gauge
line compensation
Bridge compensation (prerequisite: no force)
fully compensated
R3=R4
Same as α, β, k, R0
Same material
Same temperature compensation
Strain gauge compensation
Selective
Use own temperature to select α, k0, βs
Disadvantage: one strain gauge corresponds to one material
Bimetal sensitive gate
Composition of metal wires with different temperature coefficients
Adjust the length of the sensitive gate
Thermistor compensation
Negative temperature coefficient thermistor
Resistance strain gauge measurement circuit
DC bridge
Circuit composition
It consists of four bridge arms R1, R2, R3 and R4 and a bridge power supply U
Circuit characteristics
When there is no change in the measured value, the four bridge arms meet a certain relationship and the output is zero; when the measured value changes, the balance of the measuring bridge is destroyed and there is a voltage output.
Bridge balance conditions
The ratio of the resistances of two adjacent arms should be equal, or the product of the resistances of two opposite arms should be equal.
Voltage sensitivity
When the relative change amount of bridge voltage U and resistance ΔR1/R1 is constant, the output voltage and sensitivity of the bridge are also constant and have nothing to do with the resistance value of each bridge arm resistor.
nonlinear error
rL
Elimination method: half-bridge differential, full-bridge differential
half bridge differential
Uo has a linear relationship with ΔR1/R1, there is no nonlinear error, and the bridge voltage sensitivity KU=E/2 is twice that of single-arm operation.
Full bridge differential
The bridge differential circuit not only has no nonlinear error, but its voltage sensitivity is 4 times that of monolithic operation.
Insufficient DC bridge
When the strain gauge R1 is working, its resistance value changes very little, that is: △R1 is very small, and the corresponding output voltage of the bridge is also very small, that is, Uo is very small. Therefore, it is generally necessary to add an amplifier for amplification. The input impedance of the amplifier is much greater than the output impedance of the bridge. At this time, the bridge is still regarded as open circuit, and Uo is basically unchanged.
AC bridge