FSR Pressure Sensor RFQ: Sensitivity Without a Load Range Is Not a Specification

An FSR pressure sensor RFQ needs a load window, not only a request for “high sensitivity.” Define the lightest event that must be detected, the normal operating band, the highest expected load, and the overload that the assembly must survive. Then state the active area, actuator shape, preload, backing, readout circuit, and whether the output is used for presence, threshold, trend, or calibrated relative force. Without those inputs, two samples can produce different curves even when both sensors are working as designed. Start with the custom FSR pressure sensor options and treat the assembled mechanism as part of the sensor specification.

Why sensitivity and range are a current design question

A peer-reviewed paper published online on August 10 reports an all-PET piezoresistive pressure sensor designed to combine sensitivity, range, and durability. Its sensing mechanism changes across three loading regimes as contact develops, a porous structure compresses, and the conductive network becomes denser. The research is useful because it makes a common engineering tradeoff visible: response is not one constant number across every pressure.

The paper is not a Baoshengda specification, and its materials, construction, test fixture, 500 kPa range, and cycle results cannot be transferred to a custom FSR quotation. A buyer should take a narrower lesson from it. If the application covers more than one loading regime, the RFQ must describe the useful part of the curve and the mechanical conditions that create it. Asking only for “maximum sensitivity” leaves the supplier to guess where the product must switch, measure, or recover.

Translate the application into four load points

Begin with four numbers or bounded estimates:

1. Minimum detectable load: the lightest real event that must be separated from electrical noise, film relaxation, assembly preload, and normal vibration.

2. Normal operating band: the range in which the controller makes its main decision. This is more useful than a single demonstration force.

3. Maximum expected load: the highest repeated load during normal use, including variation in the actuator and user or machine input.

4. Overload or abuse condition: the temporary load the stack may see during installation, impact, misuse, or enclosure closing, together with the required recovery check.

Use force in newtons when the application controls total load. Use pressure only when the loaded area is defined and repeatable. If the buyer states 20 kPa but the supplier does not know whether a 5 mm pin or a 50 mm pad applies it, the physical test condition is still incomplete.

Preload also belongs in this list. Foam, a spring, a gasket, a tight cover, or a curved mounting surface can apply force before the intended event begins. That initial load may consume part of the useful response window or create a nonzero baseline. Record preload as a measured force, compression, or assembled baseline rather than describing the stack as simply “tight.”

Force, pressure, and contact geometry are not interchangeable

An FSR responds through its complete load path. The actuator decides where and how the external load reaches the sensing zone. A small hard boss can concentrate load. A wide elastomer pad can spread it. A domed button can change contact area as travel increases. A tilted part can load one edge first. The same nominal force can therefore produce a different resistance curve.

Freeze these mechanical details before comparing suppliers or sample revisions:

• actuator material, diameter or contact footprint, edge radius, hardness, and permitted travel;
• active sensing-zone outline and the actuator’s position tolerance over it;
• cover, foam, spacer, adhesive, or protective film between the actuator and sensor;
• rigid, flexible, textured, or curved backing under the sensor;
• expected bending direction and minimum bend region outside the active area;
• whether the assembly applies constant preload, intermittent presses, slow dwell, or rapid cycles.

Do not use a finger press as the acceptance fixture unless finger operation is the actual controlled use condition. A fingertip varies in contact area, speed, angle, and peak load. It can show that a sample responds, but it cannot establish a repeatable quotation range.

Use this decision table before requesting samples

This table also prevents a common purchasing error: treating a resistance value as an intrinsic property independent of the mechanism. Resistance is observed under a stated force, contact geometry, timing, temperature, readout, and history.

Freeze the mounting and readout before comparing curves

A useful sample test keeps the mechanical stack and electrical circuit fixed. Mount the sensor to the intended substrate or a close fixture. Use the specified adhesive coverage and backing stiffness. Route the tail through the intended bend and strain-relief area. Connect the same mating part and pin assignment planned for production.

On the electrical side, state the supply, pull-up or pull-down resistor, measurement node, ADC range, sample rate, filtering, and decision logic. If the project uses resistance directly, state how it is calculated. If firmware uses counts or voltage, keep that method constant for every sample. A supplier curve produced with one divider resistor should not be compared directly with a controller reading from another circuit.

Also define the time element. A fast threshold press, a sustained occupancy load, and a slow squeeze are different tests. Record application rate, dwell, release time, and the allowed return window. If the application needs relative force tracking, include rising and falling data so hysteresis is visible. If it only needs presence detection, set pass and fail thresholds with margin rather than demanding calibration that the mechanism cannot maintain.

Approve a sample matrix, not a one-point demonstration

Build the sample plan around the decision the equipment must make. At minimum, test below the detection threshold, near the threshold, through the normal band, at the upper normal load, and after a defined overload. Repeat the sequence across several units and several cycles. Record both loading and unloading.

For an assembled product, add the expected variation sources one at a time:

• actuator position at nominal and tolerance limits;
• minimum and maximum assembly preload;
• production backing and adhesive condition;
• room temperature plus the relevant hot or cold limit;
• short press versus required dwell;
• fresh sample versus a defined cycling checkpoint;
• tail in its installed route rather than lying flat on the bench.

The acceptance document does not need to promise a perfectly linear curve. It needs a usable window. Define which readings must stay below a reject limit, which must cross a decision threshold, and how much separation is required between neighboring states. Keep the raw fixture data so a later material, actuator, adhesive, or firmware revision can be compared with the approved baseline.

Supplier boundary and application limitations

Baoshengda can review a custom sensor outline, active zones, printed circuit, tail, connector, film stack, and sample structure. It can also build samples for an agreed mechanical and electrical test condition. The equipment owner remains responsible for the final load path, system calibration, controller thresholds, functional safety, and validation in the finished product.

Do not use a research-paper performance number, a catalog curve, or a loose-film bench press as proof of performance in a different assembly. Final acceptance must use the project’s actuator, backing, preload, circuit, environment, and decision criteria. If the application is safety-related or used for legal measurement, identify the applicable system-level requirements before the sensor design is released.

FSR pressure sensor RFQ checklist

Send the following package before asking for a firm sample plan:

• sensor outline, active-zone geometry, datums, mounting holes, and installed position tolerance;
• minimum detectable load, normal operating band, maximum repeated load, and overload condition;
• force or pressure units, with loaded area defined whenever pressure is used;
• actuator material, shape, footprint, hardness, travel, edge radius, and position tolerance;
• substrate, backing stiffness, adhesive coverage, cover film, foam, gasket, and expected preload;
• static, intermittent, dwell, or dynamic duty and the required release or recovery time;
• tail direction, bend zone, length, connector, pin assignment, and rear clearance;
• supply voltage, divider resistor, ADC or measurement method, sampling, filtering, and decision thresholds;
• operating temperature, humidity, cleaning exposure, and expected cycle checkpoint;
• sample quantity, fixture drawing, loading sequence, recorded outputs, and pass or fail windows;
• whether the output is for presence, threshold, relative trend, or calibrated relative force;
• responsibility boundary for fixture, calibration, firmware, equipment validation, and production change control.

When those inputs are ready, send the drawing and load-window checklist for an FSR quotation. A defined operating band gives the supplier a testable target and gives the buyer a fair basis for comparing samples, revisions, and production lots.