
PTC-01
Software for MLX90215
PTC-01 Programmer User’s Manual Rev 1.2 15/NOV/2001 Page 13
The Auto-Calibration Setup
To use auto-calibration the user must first configure the parameters specific to the application. To do this
enter the auto-calibration setup window. The setup window can be accessed by selecting “setup” from the
actions menu or by clicking the “setup” action button.
The auto-calibration routine use two points to calculate the slope and one point for the offset. The process
consist of calculating the slope between two points and shifting the slope to hit a specified point. The points
used for calibration are in the setup window and must be configured by the user. The setup widow is shown
below. The parameters entered are an example of a setup for calibrating a rotational-position sensor using
the MLX90215.
The auto-calibrate setup has four sections, input parameters, output parameters, transfer function, and offset
calculation. All of the parameters are required for the auto-calibration to work properly. The setup parame-
ters are saved when the device session is saved.
Input Parameters
The Input parameters help define the measurement range for the application. There are three required in-
put parameters, Units, Min, and Max. Units represent the media the application is sensing. The example
above is for a rotational-position sensor measuring degrees of rotation. The units are not used in any calcu-
lation but help define the transfer function and other terms and displays. Min represents the minimum set-
point of the application. For this example the min set-point is –45 degrees. Similarly Max is the max set-
point of the application and is set to 45 degrees for this example. During the calibration process the user will
be asked to set the sensor to min and max set points. It is recommended that the set-points chosen can be
achieved and are repeatable. Also note the two input set-points are used to calculate the sensitivity or gain.
Proper selection of these points will help to reduce errors caused by non linearity.
Output Parameters
The output parameters help define the output range of the sensor. The min and max output settings should
correspond to the min and max input. In this example the user wants a sensor output of 1.0 Volts and at -45
degrees and 4.0 Volts at 45 degrees.
Transfer Function
In this section the software calculates the linear transfer function using the input and output parameters.
The span is defined as the maximum minus the minimum. The sensitivity is calculated as the output span
divided by the input span.