Use of adhesive: If force is applied over an area which includes the adhesive, the resulting response characteristic will be drastically altered.) In an extreme case (e.g., a large, flat, hard actuator that bridges the bordering adhesive), the adhesive can present FSR actuation

Actuation cycle time: FSR mechanical settling time = on the order of seconds

FSR application type: 1) Force switch = the number of force threshold in one. 2) Dynamic force measurement = changing force measurement

Force accuracy calibration: Error spread measurement

Part calibration: For increased accuracy. Circuit gain adjustment for each FSR. Or each FSR's resistance is tested and select only usable units.

Temperature compensation

Spurious results: Due to sensor error or system error

- Do's and dont's

Avoid air bubbles and any contamination for the FSR laminating surface.

Use of double-sided laminating adhesives: Cover the entire surface of the sensor.

Prevent kinks and dents in active areas.

Do not kink or crease the tail of the FSR device if you are bending it; this can cause breaks in the printed silver traces. The smallest suggested bend radius for the tails of evaluation parts is about 0.1” [2.5 mm]. In custom sensor designs, tails have been made that bend over radii of 0.03” (0.8 mm]. Also, be careful if bending the tail near the active area. This can cause stress on the active area and may result in pre-loading and false readings.

Do not block the vent. FSR devices typically have an air vent that runs from the open active area down the length of the tail and out to the atmosphere. This vent assures pressure equilibrium with the environment, as well as allowing even loading and unloading of the device. Blocking this vent could cause FSRs to respond to any actuation in a non-repeatable manner. Also note, that if the device is to be used in a pressure chamber, the vented end will need to be kept vented to the outside of the chamber. This allows for the measurement of the differential pressure.

Do not exceed 1mA of current per square centimeter of applied force (actuator area). This can irreversibly damage the device.

11. Ohmite FSR integration guide

- FSR types: Shunt mode, thru mode

- Shunt mode

Shallower curve giving better control esp. at higher forces i.e. >100g

Fewer print layers and less silver ink required so typically cost is < Thru Mode sensors

- Thru mode

Force range is limited typically <0.5-1kg

More print layers and more silver ink required so typically cost is greater then shunt mode

- Interconnection

Bare tail

Crimpfl ex series: solder tabs, female and male connectors

Friction fit: ZIF, TIF, gold / tin / nickel pins

Friction fit with protective overprint

Housing including standard, latch and detent

Other options

- FSR types

Single point: Z axis force only. Square, round, strip. Single senor or sensor array

Linear potentiometer: Strip or scroll-wheel configuration. X or Y position with Z-axis force (1D)

3D single-touch: X & Y positions on a single touch

3D multi-touch: Track pad for X & Y positions on multiple touch points