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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?

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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.

For your specific case, here is the product site. Under technical documents, you will find datasheet.

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.

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  • \$\begingroup\$ thanx 4 ur suggestions..... \$\endgroup\$ – user3633 Mar 30 '11 at 5:31
  • \$\begingroup\$ u hav said that Accuracy is related to voltage, means temperature is changing with respect to volatge, if yes , then can i measure this voltage, do i hv to measrure it from pin Tout? \$\endgroup\$ – user3633 Mar 30 '11 at 5:41
  • \$\begingroup\$ @yaprisu Accuracy is related to operating voltage of the sensor. That voltage should be measured on pins 8 (Vdd) and 4 (GND). If the voltage is between 3 V and 5 V, accuracy is $±\frac{1}{2}^\circ C$. Between 2.7 V and 3V, you get $±1^\circ C$. If you're measuring temperatures below $0^\circ C$ and above $70^\circ C$, accuracy is $±2^\circ C$. \$\endgroup\$ – AndrejaKo Mar 30 '11 at 8:41
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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.

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  • \$\begingroup\$ thanx 4 answering my question.... \$\endgroup\$ – user3633 Mar 30 '11 at 5:19
  • \$\begingroup\$ thanx 4 answering my question.... i already tried ice, but after 9 degree C, LCD went off.so i didn't go 4 boil water but used soldering iron 2 show dat ckt is working. can u please tell me hw can i check temp of liquids like water with this ic? \$\endgroup\$ – user3633 Mar 30 '11 at 5:30
  • \$\begingroup\$ @yaprism, are you submerging your circuit? \$\endgroup\$ – Thomas O Mar 30 '11 at 6:44
  • \$\begingroup\$ @yaprisu What it ckt? \$\endgroup\$ – AndrejaKo Mar 30 '11 at 9:03

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