Sensing technology and system configuration

AMTI utilizes two types of sensing technologies in its products: Hall Effect and strain gage. Each offers distinct benefits and requires a unique hardware setup.

Hall Effect

Hall Effect force plates and force sensors are economical, lightweight, portable instruments that function as standalone systems for specific applications. Their patented design uses Hall Effect sensors to measure all six force components and allows for high overload protection on all axes.

Multiple Hall Effect sensors and magnets are arranged inside the force transducer. The sensors measure magnetic field changes that occur when integrated spring elements deflect due to the forces and moments acting upon the top surface.

Signal amplification occurs inside AMTI’s Hall Effect-based products, eliminating the need for an external amplifier and limiting the necessary system components to an analog or digital data cable. If the digital output is used, an interconnection box may be used to connect two force plates or force sensors to a computer.

Mounting is possible with Hall Effect force plates, but is typically unnecessary for the recommended applications.

The trade-off for this simple design is lower sampling rates and less stiffness, which results in lower natural frequency of the platform top.

Strain gage

Most of AMTI's products use strain gage technology, which provides the most accurate and flexible force measurement solution. (Hall Effect platforms offer comparable measurement performance when employed for their intended use.)

The working surface of an AMTI strain gage-based product is supported by thin-walled cylindrical sensing elements. Each element is instrumented with strain gages, which are excited by a constant, user-selectable, voltage supplied by the connected signal conditioner.

When a load is applied to the working surface of the transducer, strains occur in the walls of the supporting cylinders. This changes the electrical resistance of the strain gages and produces a change in the output voltage that is proportional to the forces being applied. AMTI's patented arrangement of strain gages isolates the signals caused by individual forces and moments, allowing them to be accurately and separately quantified.

Signal Conditioner

An AMTI signal conditioner is required for use with each strain gage force platform or force sensor. The signal conditioner provides the required excitation voltage to the strain gage elements. It then amplifies and conditions the returned signal to produce an output that is ready for use by a computer or other data acquisition system.

Cable

The force plate or force sensor is connected to the signal conditioner via a 100-percent-double-shielded cable, which uses twisted pair conductors for signal sensing and excitation to provide the highest possible noise immunity. AMTI manufactures a large variety of cables and connector combinations and routinely makes custom cables to meet customers' needs. For more information regarding cables and connectivity options, visit the cable selection guide page.

Mounting

Proper mounting of strain gage force plates and force sensors is important as their bases are required to be flat, rigid and level for optimal results. Force plates, however, may be left freestanding for activities with low shear forces, such as balance studies. Please see the Force Plate Mounting Options and Force Plate Layout Examples pages for more details.
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