Temperature sensor application description

AN3397

14/24

Doc ID 018809 Rev 1

Note:

In any application, a user may decide to make a trade-off and use the V90 datasheet typical

value and the user calibration point to obtain less accurate but nevertheless very good

temperature calculation results.

2.4.3

Calibration technique

The calibration technique is a one-off procedure which must be done when the STM8L-

DISCOVERY is received. It consists of calculating the average slope of the TS, and is

available only when the TS application Advanced mode is selected.

The calibration technique makes use of Equation 5 to calculate the average slope.

The factory calibration value, V90, is obtained from a fixed data address (see Advanced

a thermometer. The #define Tambient must be updated with the temperature given by

the thermometer.

application code.

To start the calibration procedure, press the user push-button for at least 2 s, then release

the button. If calibration is successful, the message ‘CAL-OK’ is displayed on the LCD

screen. If no factory calibrated value is present, or if the present value is out of range (580

mV - 614 mV), the message 'CALERR' is displayed. Press the user push-button again to

continue. When calibration is successful, the value is stored in the Data EEPROM of the

microcontroller. By default, the value is stored as two bytes in the Data EEPROM addresses

0x1000 (MSB) and 0x1001 (LSB).

In Advanced mode, an automatic calibration is performed by the software if no calibration

has been made by the user.

Note: