Vibrating Wire Embedment Strain Gage is designed to measure valid strain in concrete after embedded in concrete structure. 
Once the gauge is strained, frequency of vibrating wire is changed.
At this time, plucking coil generates resonance frequency and it is delivered to measuring instrument.

The Strain in concrete transmit to the body and vibrating wire, when tensile and pressure occur, if vibrating wire is magnetized by plucking coil then vibrating wire output resonance frequency. This frequency transmits to an output device and shows with engineering unit. 
Then it can count with the pressure or strains using modulus of conversion.