Strain sensors

Mechanical loading on a component by a force leads to a mechanical tension, Formula: σ = F–A , and to a strain, Formula: ε = Δ—l lo. As strain is a relative change in length of the loaded component, it is dimensionless. In most applications, strain measurement is used as a means of measuring the force on a component indirectly. The advantage of this is that the component undergoes practically no change as a result of the installation of the sensor, which is very small in size compared with the sensors used for direct measurement. In contrast to direct measurement of force, the strain measuring signal is dependent on the
force application point.

The strain is measured either at the surface or directly inside the structure.

The piezoelectric surface strain sensor is secured to a suitable point on the surface of the component with a single screw.

The mounting screw transmits the force between the two contact surfaces of the sensor and the component by stiction. A change in the longitudinal measurement of the component is transferred to the elastic element of the sensor, where it acts as a shear force on a piezoelectric sensor element. In complex structures, the right mounting point for the surface sensor must be determined by trial and error.

Strain sensors installed inside the structure require a cylindrical bore for mounting purposes. The advantage of this is that the measuring element can be placed where conditions are optimal. Since strains occur in different directions, Kistler offers sensors which measure strains which act lengthwise or crosswise in relation to the mounting bore. To enable these sensors to measure both tensile and compression strains, they are mechanically preloaded in the mounting bore.

Compared with conventional strain measurement technology, piezoelectric strain sensors are extremely sensitive.

Sensor, surface mounted

Strain sensor «HighSens» Type 9232A
Type	Measuring	Sensitivity	Natural	Operating	L	W	H	Weight
	range			temperature
Uncalibrated	µε	pC/µε	kHz	°C	mm	mm	mm	g
9232A	±600	≈-80	≥12	0 … 70	40	17	15	50
Characteristics Very high sensitivity, extremely low acceleration sensitivity, also suitable for measurements on moving parts, safe against overload, degree of protection IP 65 (with connecting cable)			Applications Indirect force measurement on mechanical presses, machine tools, fast-running production machinery, automatic assembly machinery			Accessories Connecting cable Type 1979A…, 1635C…

Strain transmitter Type 9234A...
Type	Measuring	Sensitivity	Operating	L	B	H	Weight
	range		temperature
Uncalibrated	µε	mV/µε	°C	mm	mm	mm	g
9234A...	±600	≈17…1700	-10 … 70	63,5	21	17	93
Characteristics Very high sensitivity, extremely low acceleration sensitivity, integrated load amplifier, adjustable via remote control, safe against overload, degree of protection IP 65 (with connecting cable)			Applications Indirect force measurement on mechanical presses, machine tools, fast-running production machinery, automatic assembly machinery		Accessories Connecting cable Type 1787A..., 1789A..., 1700A66/68

Strain sensor Type 9233B…
Type	Measuring	Sensitivity	Natural	Operating	L	W	H	Weight
	range		Frequency	temperature
Calibrated	µε	pC/µε	kHz	°C	mm	mm	mm	g
9233B…	±300	≈-6	≈4	-30 … 100	38	22	30	210
Characteristics High sensitivity, mounting screw M6, safe against overload, corrosion-resistant, unlimited service life under changing load, degree of protection IP 67 (with cable Type 1915A…)			Applications Indirect force measurement on presses.			Accessories Connecting cable Type 1913A..., 1917A…, 1915A… T-adapter Type 1700A1 Protective cover Type 9437A…

For more information about other products of strain sensors, please download this catalog.

Back