Contents
How is a strain gauge noisy?
Strain measurements must often be made in the presence of electric and/or magnetic fields which can superimpose electrical noise on the measurement signals. This technical note identifies some of the more common noise sources, and describes the routes by which the noise is induced into strain gage circuits.
What happens when a strain gauge is stretched?
Metal strain gauges typically have gauge factors of the order of 2.0. When such a strain gauge is stretched its resistance increases, when compressed its resistance decreases. Thus the gauge on the upper surface increases in resistance while that on the lower surface decreases.
How do you increase the sensitivity of a strain gauge?
For the same strain gage, changing the bridge configuration can improve its sensitivity to strain. For example, the full-bridge type I configuration is four times more sensitive than the quarter-bridge type I configuration. However, full-bridge type I requires three more strain gages than quarter-bridge type I.
What are the advantages of strain gauges?
The main advantages of mechanical strain gauges are the ease with which they can be used, their relatively low cost and the fact that they are reusable. Electrical resistance strain gauges overcome most of the disadvantages of mechanical gauges.
Why is strain gauge bridge sometimes excited with AC?
The bridge network is excited by a voltage applied across the opposite corners, the voltage can be AC or DC. AC voltages can have the advantage that low DC outputs are not adversely affected by DC offsets, but the most commonly used voltage source is DC since it is more readily available and easy to measure.
Is a strain gauge a variable resistor?
A strain is simulated by modifying the variable resistor so a voltage appears on the bridge output and is detected by the Strain Gauge measuring device connected to the bridge output. The resistor values used in the bridge in user systems can have a variety of values.
Why do you need a strain gauge amplifier?
In summary, strain gauges often need instrumentation differential amplifiers to boost the low-level measurement signals while canceling out any attendant noise. Many companies provide strain gauge signal condition instrumentation amplifiers and other required filters and electronics in one package.
What causes noise in a strain gage circuit?
Virtually every electrical device that generates, consumes, or transmits power is a potential source for causing noise in strain gage circuits. And, in general, the higher the voltage or current level, and the closer the strain gage circuit to the electrical device, the greater will be the induced noise.
How does a strain gauge transducer work?
As a transducer, which converts a measured analog quantity into an electrical signal, the strain gauge consists of a high-resistance, fine-wire, or thin-foil grid that is securely bonded to a specimen. When the specimen undergoes a stress, the resistance of the strain gauge is changed.
How is the resistance of a strain gauge measured?
In an ideal case, the strain gauge is the only resistor in the circuit that varies and then only due to a change in strain on the surface of the specimen to which it is attached. The unknown strain gauge resistance Rx is to be measured; resistances R1 , R2, and R3 are known, where R2 is adjustable if needed.