Normal Range for Strain Gauge Readings on a Car Suspension
Procedure for Selecting the Right Strain Gauges
Before the right strain gauge can be selected, the measurement goal needs to be clearly set. The main question to be considered is whether the strain gauge will be used for experimental tests, immovability tests or for transducer manufacturing.
The strain approximate selection for experimental examination will exist done regarding the following selection criteria:
| 1. Geometry: | Number and position of grids (blueprint) |
| two. Strain guess series: | Construction of strain gauge |
| 3. Connections: | Type and position |
| 4. Temperature response adaptation: | Material to which strain gauge temperature response is matched |
| 5. Active grid length: | in mm |
| 6. Electrical resistance: | in Ohm |
1. Geometry of the Strain Gauge
2. Strain Gauge Series
HBM offers different strain gauge series for strain measurement. Strain estimate serial are divers by the combination of strain judge carrier (e.g. Polyimide) and the measuring grid foil (eastward.g. Constantan). All strain gauges within a strain judge serial offer the same carrier and measuring filigree foil cloth. Therefore many specifications are identical for one strain gauge serial.
For experimental tests robust and flexible strain gauges, which can be used under arduous atmospheric condition, have singled-out advantages. Strain gauges having the synthetic, polyimide, as carrier fabric for the measuring grid and with the series identification "Y" are in this category. This series contains a large number of different types of strain gauges used for a variety of tasks in experimental tests. There are also numerous special types of strain gauges, e.one thousand. hole-drilling and band core rosettes for the conclusion of residual stresses in structural parts and strain judge bondage for the investigation of stress distribution on complex structures.
3. Connections
HBM offers strain gauges with unlike connectedness configurations.
 | Integrated solder tabs (east.1000. LY4)
|
 | Big solder tabs with strain relief (due east.yard. LY6)
|
 | Ni-plated copper leads, uninsulated, approx. 30 mm (1.eighteen inch) long (east.g. LY1)
|
 | Fluoropolymer-insulated connection wires, approx. 50 mm (1.97 inch) long (east.one thousand. K-C LY4)
|
 | Fluoropolymer-insulated connexion wires, approx. fifty mm (1.97 inch) long (e.g. K-C LY4)
|
4. Temperature Response Adaptation
Strain gauges that are connected individually in a Wheatstone quarter bridge circuit volition show an output signal if the temperature changes. This signal is called "apparent strain" or "thermal output" and is independent of the mechanical load on the examination object.
Still, it is possible to adjust a strain gauge to the thermal expansion coefficient of a specific material, such that the output signal is very small in case of a temperature change. Such strain gauges are called strain gauges with "matched temperature response" or "cocky-compensated" strain gauges.
To benefit from their matched temperature response, strain gauges must be selected to the thermal expansion coefficient a of the test fabric.
| Code | Material | Thermal expansion coefficient ∝ |
| 1 | Ferritic steel | 10.8 ⋅ ten-6/One thousand (6 ⋅ ten-6/°F) |
| iii | Aluminum | 23 ⋅ 10-vi/1000 (12.8 ⋅ x-6/°F) |
| 5 | Austenitic steel | 16 ⋅ x-6/1000 (8.9 ⋅ 10-vi/°F) |
| 6 | Quartz glass / blended | 0.v ⋅ x-half-dozen/K (0.3 ⋅ x-6/°F) |
| 7 | Titanium / gray cast iron | 9 ⋅ x-6/G (v ⋅ 10-6/°F) |
| 8 | Plastic | 65 ⋅ 10-6/K (36.1 ⋅ 10-6/°F) |
| ix | Molybdenum | 5.four ⋅ 10-6/K (3 ⋅ 10-6/°F) |
5. Active Grid Length
The strain gauge measuring grid length depends on the aim of measurements, as the result of the measurement using strain gauges volition be the hateful strain underneath the measuring grid. In full general, measuring grid lengths of 3 or 6 mm (0.118 or 0.236 inches) represent a good solution.
Long measuring grids are recommended where in that location is an inhomogeneous cloth, such as concrete or forest. A long strain gauge volition bridge the inhomogeneities of the work piece and, as a measurement outcome, will supply the strain underneath the measuring grid.
Short measuring grids are suitable for detecting a state of local strain. They are therefore suitable for determining strain gradients, the maximum point of notch stresses and similar stresses.
half dozen. Electrical Resistance
HBM strain gauges are available in 120, 350, 700 and i,000 Ohm versions. The selection of the resistance depends on the constraints of the measurement task. Other resistances are available on request.
| Low Ohm strain gauges | High Ohm strain gauges |
| + Lower influence of electromagnetic interferences | + Lower influence of electric resistance in connectedness paths (sideslip-rings, cables,...) |
| + Lower influence of a change in isolation resistance | - "Meliorate" antennas in the case of interferences |
| - College power requirement | - Higher influence of a alter in isolation resistance |
| - More cocky-heating due to higher current menstruum compared to loftier Ohm strain gauges |
Application report
Influence of resistance and other parameters on the temperature at the measurement bespeak
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Selection Guide for Strain Gauges for Experimental Tests
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Source: https://www.hbm.com/en/7164/how-to-find-the-right-strain-gauge/
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