Force Sensing Resistor FSR400S Series

FSR™ 400 series is part of the single zone Force Sensing Resistor™ family. Force sensing resistors, or FSRs, are robust polymer thick film (PTF) devices that exhibit a decrease in resistance with increase in force applied to the surface of the sensor. This force sensitivity is optimized for use in human touch control of electronic devices such as automotive electronics, medical systems, and in industrial and robotics applications.

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Description

The standard 400 sensor is a round sensor 7.62mm in diameter. Custom sensors can be manufactured in sizes ranging from 5mm to over 600mm. Female connector and short tail versions can also be ordered.

Features

• Actuation force as low as 0.1N and sensitivity range to 10N.
• Easily customizable to a wide range of sizes
• Highly repeatable force reading; as low as 2% of initial reading with repeatable actuation system
• Cost effective
• Ultra thin; 0.35mm
• Robust; up to 10 million actuations
• Simple and easy to integrate

Applications

• Detect & qualify press – Sense whether a touch is accidental or intended by reading force
• Use force for UI feedback – Detect more or less user force to make a more intuitive interface
• Enhance tool safety – Differentiate a grip from a touch as a safety lock
• Find centroid of force – Use multiple sensors to determine centroid of force
• Detect presence, position, or motion – Of a person or patient in a bed, chair, or medical device
• Detect liquid blockage – Detect tube or pump occlusion or blockage by measuring back pressure
• Detect proper tube positioning
• Many other force measurement applications

Device Characteristics

Application Information

FSRs are two-wire devices with a resistance that depends on applied force.

For specific application needs please contact Interlink Electronics support team. An integration guide is also available.

For a simple force-to-voltage conversion, the FSR device is tied to a measuring resistor in a voltage divider configuration (see Figure). The output is described by the equation:

In the shown configuration, the output voltage increases with increasing force. If R_FSR and R_M are swapped, the output swing will decrease with increasing force.

The measuring resistor, R_M, is chosen to maximize the desired force sensitivity range and to limit current. Depending on the impedance requirements of the measuring circuit, the voltage divider could be followed by an op-amp.

A family of force vs. V_OUT curves is shown on the graph below for a standard FSR in a voltage divider configuration with various R_M resistors. A (V+) of +5V was used for these examples.