| ??? 11/26/09 15:29 Read: times |
#171201 - Self-heating? Responding to: ???'s previous message |
Yash said:
The output of the ADC is changing with temperature. However, the LCD shows 43 degrees celcius when the actual temperature here in Mumbai is 30 degrees. Is this error allowed? What do you think?? This can be answered by yourself, dear Yash, can't it... The best would be, you will show us your schematic. Sometimes this error comes from self-heating effects, when using an NTC or the KTY-sensor series, for instance, and choosing a too high measuring current, or by putting the sensor near something that can heat up the sensor. Usually, there are two ways to calibrate such a sensor, by hardware (pots and trimmers) or software. You could write a routine, which just displays the result of conversion as a number between 0 and 255. Now you drop your sensor into ice water and boiling water and determine which ADC numbers corrspond to these temperatures. Then you could write a program, which generates a linear interpolation between these two points. If the sensor is linear enough, this can work very well. Of course, you can do this with any other temperature range you want, but then a precise reference temperature meter would be needed. Yash said:
P.S Can you suggest some other 8 channel ADC which wouldn't be so heavy on the wallet? There are 8051s on the market, which already contain such a multi-channel-ADC. NXP has them, Analog Devices with the ADuc-series, SILABS, etc. etc. Kai Klaas |
| Topic | Author | Date |
| Receiving output from ADC0848. | 01/01/70 00:00 | |
| Don't feed other pins without VCC | 01/01/70 00:00 | |
| CS and RD working. | 01/01/70 00:00 | |
| Wrong understanding of ADC! | 01/01/70 00:00 | |
| But according to Mazidi... | 01/01/70 00:00 | |
| No, you don't! | 01/01/70 00:00 | |
| Sorry! | 01/01/70 00:00 | |
| How do you see that? | 01/01/70 00:00 | |
| The LCD shows a 255. | 01/01/70 00:00 | |
| But this can have zillions of reasons... | 01/01/70 00:00 | |
| Never retype source code when posting | 01/01/70 00:00 | |
| Working! But with errors... | 01/01/70 00:00 | |
| You must convert raw ADC reading into temperature | 01/01/70 00:00 | |
Self-heating? | 01/01/70 00:00 | |
| Configured as push-pull? | 01/01/70 00:00 | |
| It's a P89v51RD2 | 01/01/70 00:00 | |
| Difference only noticeable if contention | 01/01/70 00:00 | |
| then STOP what you are doing | 01/01/70 00:00 |