Calibration

Kitronyx pressure mapping systems output raw digital values which correspond to applied pressure.

This raw ADC information is sufficient to get information about surface pressure distribution.

In some cases, a user may want to get physical pressure values from this pressure distribution information.

For this purpose, calibration process is required.

Unlike other sensors, factory calibration is very hard or impossible for pressure distribution sensors.

Instead, this kind of sensors need on-site calibration using carefully designed calibration systems which we do not offer yet.

Therefore, we generally do not recommend to use our systems to get physical pressure values.

However, if pressure information is truly required, please follow the following simple calibration process

Simple Calibration Process

1) Put a target object on a sensor. Note that the target object is an object that is used to load the sensor in actual measurement process.

2) Press the object with known total force f. Here we assume that f = 10kgf

3) Measure ADC Sum A using Snowforce. Here we assume that A = 1,000

4) Record A and f.

5) Using A and f, you can get linear equation as follows.

Simple Measurement Process

1) Measure ADC Sum A. Here we assume that measured ADC sum is 500.

2) Calculate total force f by using the equation f = 0.01A. In this case, total force f will be 5 (kgf).

3) Applied force of each sensel (f_sensel) can be computed by using the above obtained total force f.

4) Applied pressure of each sensel (p_sensel) can be calculated by dividing f_sensel by sensel area A.

NOTE

1) With the above described calibration and measurement processes, one can get rough pressure values. However this simple calibration does not give very accurate measurement result.

2) If you anyway consider to use our products to get physical pressure information, MC1509 will be more suitable than Snowboard.

Reason for not being able to produce an accurate result

1. Sensor ADC curve is not linear.

This variation of sensor response is innate characteristics of FSR sensors

2. Each sensel has different response.

This can be remedied by using an equilibration device and an appropriate calibration software.

Simply speaking, all sensels of a sensor are evenly pressed using an equilibration device and responses of each sensel is collected by a software which tunes gains of sensels.

Our commercial software ForceLAB 2 has this gain tuning feature but we do not yet sell the equilibration device officially.

If you have a press machine or air bladder you can use these machines as an equilibration device.

Any machines that can evenly press the sensor can be regarded as an equilibration devices.