Tekscan FlexiForce A201 Variable Resistance Sensors

The FlexiForce A201 variable resistance sensors can be used with Biometrics DataLINK and DataLOG systems, Thought's ProComp2, ProComp Infiniti and FlexComp Infiniti systems, as well as customer data acquisition systems.

The FlexiForce A201 force sensor is an ultra-thin, flexible printed circuit. The force sensors are constructed of two layers of substrate (polyester/polyimide) film. On each layer, a conductive material (silver) is applied, followed by a layer of pressure-sensitive ink. Adhesive is then used to laminate the two layers of substrate together to form the force sensor. The active sensing area is defined by the silver circle on top of the pressure-sensitive ink. Silver extends from the sensing area to the connectors at the other end of the sensor, forming the conductive leads. A201 sensors are terminated with male square pins, allowing them to be easily incorporated into a circuit. The two outer pins of the connector are active and the center pin is inactive.

8" A201 Sensor

The FlexiForce single element force sensor acts as a force sensing resistor in an electrical circuit. When the force sensor is unloaded, its resistance is very high. When a force is applied to the sensor, this resistance decreases. The resistance can be read by connecting a multimeter to the outer two pins, then applying a force to the sensing area. In the image below, the plot shows both the Force vs. resistance and Force vs. conductance (1/R). Note that the conductance curve is linear, and therefore useful in calibration.

One way to integrate the A201 force sensor into an application is to incorporate it into a force-to-voltage circuit. A means of calibration must then be established to convert the output into the appropriate engineering units. Depending on the setup, an adjustment could then be done to increase or decrease the sensitivity of the force sensor. The chart to the right shows a typical sensor response (based on our recommended drive circuit shown below).

Specifications & Features

Physical Properties
Thickness	0.008" (.208mm)
Length	8" (203mm) 6" (152mm) 4" (102mm) 2" (51mm)
Width	0.55" (14mm)
Sensing Area	0.375" diameter (9.53mm)
Connector	3-pin male square pin
Thickness	0.008" (.208mm)
Typical Performance
Linearity Error	< ±3%
Repeatability	< ±2.5% of full scale (conditioned sensor, 80% force applied)
Hysteresis	< 4.5% of full scale (conditioned sensor, 80% force applied)
Drift	< 5% per logarithmic time scale (constant load of 90% sensor rating)
Response Time	< 5 microseconds
Operating Temperatures	15°F - 140°F (-9°C - 60°C)
Force Ranges	0-1 lb. (4.4 N) 0-25 lbs. (110 N) 0-100 lbs. (440 N)*
Temperature Sensitivity	Output variance up to 0.2% per degree F (approx. 0.36% per degree C)

* See recommended drive circuit below. In order to measure forces above 100 lbs. (up to 1000 lbs.), apply a lower drive voltage and reduce the resistance of the feedback resistor (1 kΩ min).

Example of a FlexiForce Excitation Circuit

Optional Components

FlexiForce Female Berg Receptacle

The female berg connector is an optional component that easily connects A201 sensors (which have a male pin termination) to discrete wires or another flexcircuit.

FlexiForce Male Berg Connector

The male berg connector is an optional component that can be easily crimped to an A201 sensor that has been trimmed in length.

FlexiForce Quickstart Board

The FlexiForce Quickstart Board is a finished single voltage source circuit which can be quickly dropped into a prototype or easily designed into a product to obtain force measurements.

It is designed for easy integration of FlexiForce sensors. It provides a 0-5V analog voltage output that can be used as an input on your microcontroller or third-party data acquisition system. The Quickstart Board contains:

(1) FlexiForce Quickstart Board
- Dimensions: 1.25" x 1.25"
- Input: 3.3V - 9V
- Output: 0V - 5V nominal (Vin ≥ 5V)
(1) battery clip
(2) FlexiForce A201 sensors

Benefits:

Signal conditioning that allows the ability to adjust or modify dynamic range
Eliminates time developing circuits
Perfect for a plug and play product to drop into a design

Ordering information

Part No.	Description
A201-1-8	0-1 lb Flexiforce series sensors 8-pack
A201-25-8	0-25 lb Flexiforce series sensors 8-pack
A201-100-8	0-100 lb Flexiforce series sensors 8-pack
FLEXF-FBR	FlexiForce Female Berg Receptacle
FLEXF-MBC	FlexiForce Male Berg Connector
FLEXF-QB	FlexiForce Quickstart Board

A201 sensors can also be ordered in 2", 4", and 6" lengths for an additional fee.