HP 34970A manual HI Source HI Sense LO Sense LO Source

Chapter 8 Tutorial

Measurement Fundamentals

For more information on strain gages, refer to “Practical Strain Gage Measurements” (HP Application Note 290-1). This application note is also available on the HP Website in the Test and Measurement section (www.hp.com).

dxu °uy” uqsu qyu y rq ytu”t qyu°uu4 Sy q y

vy” wyt rut q y”qxuu rqs“yw4 dxu yu y” qyu ”yy qy yu r y ”

ratio of the foil’s strained to unstrained resistance: ε = ΔR/R.

The Yz Wz” (PO) indicates the sensitivity of a strain gage and is a measure of the fractional resistance change per strain: PO = (ΔR/R)/ε . Devices with a higher gage factor will exhibit a greater resistance change per strain applied.

Strain gages are available in many patterns with various numbers and configurations of elements. The most common element is the single gage

form shown below. Multi-element strain gages, also called , are used to measure components of strain in different directions. Two-element (90°) and three-element (45° or 60°) configurations are the most common.

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jStrain gages are used to sense many types of physical parameters. Strain gages are primarily a force-sensing device. Force is measured indirectly by measuring the deformation of a test body to a known applied force thus producing a resistance change proportional to the applied force. Many other physical quantities can be measured through force measurements. Common applications of strain gages include weight, pressure, flow, and level measurements.

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