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Force Sensor Linearity Error

Sinocera Piezotronics, INC | Updated: Oct 17, 2017

Force Sensor Linearity error

Pressure sensor with high accuracy, reasonable error requirements, the pressure sensor error compensation is the key to its application. The pressure sensor mainly has the error of offset, sensitivity error, linear error and hysteresis error. This paper introduces the mechanism of these four errors and the influence on the test results. At the same time, the pressure calibration method and application examples will be introduced to improve the measurement accuracy.

The current variety of sensors on the market, which allows design engineers can choose the system required pressure sensor. These sensors include both the most basic converters and the more complex, highly integrated sensors with on-chip circuitry. Because of these differences, the design engineer must be as reliable as possible to compensate for the pressure sensor's measurement error, which is to ensure that the sensor to meet the design and application requirements of the important steps. In some cases, compensation can also improve the overall performance of the sensor in the application.

Offset, range calibration, and temperature compensation can all be achieved through a thin film resistor network, which uses laser correction during the encapsulation process.

The sensor is usually used in conjunction with a microcontroller, and the microcontroller embedded software itself establishes a sensor mathematical model. After the microcontroller reads the output voltage, the model converts the amount of voltage to the pressure measurement by the conversion of the analog-to-digital converter.

The simplest mathematical model of the sensor is the transfer function. The model can be optimized throughout the calibration process and the maturity of the model will increase as the calibration point increases.

From a metrological point of view, the measurement error has a fairly strict definition: it characterizes the difference between the measured pressure and the actual pressure. And usually can not directly get the actual pressure, but can be estimated by using appropriate pressure standards, measurement personnel usually use those who are at least 10 times higher than the measured equipment as the measurement standard. Since the uncalibrated system can only use the typical sensitivity and offset values to convert the output voltage to pressure, the measured pressure will produce the error shown in Figure 1.

This uncalibrated initial error consists of the following parts:

offset error. Since the vertical offset remains constant over the entire pressure range, variations in converter diffusion and laser adjustment correction will produce offset errors.

b. sensitivity error, resulting in the size of the error is proportional to the pressure. If the sensitivity of the device is higher than the typical value, the sensitivity error will be the incremental function of the pressure. If the sensitivity is lower than the typical value, then the sensitivity error will be the pressure reduction function. The cause of the error is the change in the diffusion process.