FAQ on Force Sensor Performance

May 18, 2020

Here are the most common frequently asked questions about the performance of Strainsert force sensor products, including load pins, load cells, bolts/studs and tension links. Please contact us if your question is not answered below!

What are the temperature limits of the transducers?

Answer: Typical temperature range is -40° F [-40° C] to 300° F [149° C] depending on the transducer type. The maximum limits, on case by case evaluation are -65° F [-53° C] to 400° deg. F [204°C]. Designs at these limits may reduce overall performance and require special materials and/or components.

What linearity and repetition can I expect from a transducer?

Answer:  Standard Parts:  Specifications can be found on our website for the various transducers.

Custom: Non-linearity, typically 1% full scale nominal.  Non-Repeatability: +/-0.15% to: 0.5% (Depending on type of sensor and design).

B-Axial Pins: Typically 1% nominal on primary axis and a cross-talk correction algorithm is provided to improve accuracy of other positions. Typically less than 5% full scale.

What is the resolution for Strainsert Transducers?

Answer:  Resolution is a function of signal strength and output sensitivity. The output sensitivity varies with transducer design such as factor of safety and calibration load.

What is the accuracy (precision) for Strainsert Transducers?

Answer:  Strainsert does not state an “accuracy” for our products.  Accuracy is a measure which defines how close the displayed reading of a sensor or sensor system is to a known standard.  The system accuracy is dependent on the traceability of the standards used to calibrate the system.

Strainsert uses “Non-Linearity”, “Non-Repeatability” and “Hysteresis” as the measure of sensor performance.  Strainsert defines these characteristics as follows:

Performance Characteristic and Description
Non-Linearity (NL): Measure of the maximum delta between the sensor output signal and the best-straight-line through the signal output data as recorded from 0 to applied force to full scale load capacity.

Non-Repeatability (NR): Measure of the maximum delta between the sensor outputs when measured repeatedly at the same applied load.

Hysteresis (H): Measure of the maximum delta between the sensor outputs when measured at the same applied load in the ascending and the descending loading directions

Note: All characteristics are expressed as a percentage of the full scale sensor output.

Many customers view the total accuracy as the root mean square of the non-linearity, repeatability, and hysteresis.

+/- Error = √ NL² + NR² + H²

What is the Response Time for Strainsert Transducers?

Answer:  Research has demonstrated that the response time of foil strain gages have a response time up to 300 kHz for smaller 3mm gages, and up to 110 kHz for 10 mm gages. Strainsert transducers use grid sizes of approximately .125 to .25”. Therefore, we would estimate a response time between 110 to 300 kHz. Strainsert has not completed any testing to determine response time.

Why does the zero move (change in the unloaded reading)?

Answer:  The zero moves in all types of transducers. Overloads, impact loading, material relaxation, exposure to high temperatures, fatigue loading, or off axis loading may cause a zero shift. However, changes in zero do not typically change the span of the transducers. Therefore, if possible the unloaded readings should be “nulled” out before each measurement. If the span is changing, then the transducers should be returned for further evaluation or replacement.

Can the sensor withstand impact or vibration loading?

Answer:  As a final check Strainsert does a random vibration test. This is a short term test intended to capture any loose wire or connections. This test is not conducted in accordance with any technical or military specification. Strainsert does not have any test data that addresses impact loading or vibration. While customers have used our products in these types of applications, the specific details and the duration of their use is not known.