I have made temperature indicator using microcontroller P89V51. My temperature sensing IC is DS1621. I'm using LCD for the display..n ckt is working very fine, Do I have to calibrate this IC? If yes, then how can I?
In general the best way to find out if you need calibration is to check manufacturer's website. There you will probably be able to find product datasheet which will probably contain needed information.
If the datasheet isn't available on manufacturer's website (or there isn't any website), search for
model_number datasheet. There are several sites on the Internet which catalog datasheets, so you may be able to obtain it even manufacturer isn't providing it anymore.
On the second page, under OPERATION it is said that the sensor is already calibrated for measuring temperature in Celsius degrees, so no further calibration should be needed.
Furthermore is you read the command set part of the datasheet, you will find out that there is no command for calibration, so it should be impossible for user to calibrate the sensor.
If you are having accuracy problems, take a look at page 13 of the datasheet. Accuracy is related to voltage, as show in the DC electrical characteristics table.
You may consider the physical way. Go boil some water and make some ice. Two good calibration points for a sensor. You can use these to compensate for the error, assuming that it is linear.