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Topic: LM35 testing (Read 2922 times) previous topic - next topic

Graynomad

Quote
between 13 and 19

I imagine those temps would be difficult to come by in the Philippines.

Stick the sensor in a fridge, do the test at 2AM :), get a box of dry ice like you mentioned before and hold the sensor close until it gets to 13 degrees, use your imagination.

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Rob
Rob Gray aka the GRAYnomad www.robgray.com

janno0718


Quote
between 13 and 19

I imagine those temps would be difficult to come by in the Philippines.

Stick the sensor in a fridge, do the test at 2AM :), get a box of dry ice like you mentioned before and hold the sensor close until it gets to 13 degrees, use your imagination.

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Rob


Sir i have a question. If I get in my device a temperature measurement of 28C and in digital thermometer 26C. Can I just edit my formula in the Arduino IDE and make it subtract by 2C. Example Temp - 2. So it can match the temperature measurement in the digital thermometer

Graynomad

Yep, you can do what you like to the reading. If it is a constant 2 off then subtract 2 as you say.

If the error changes over the range you can have a lookup table and subtract different values according to the reading.

______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

janno0718


Yep, you can do what you like to the reading. If it is a constant 2 off then subtract 2 as you say.

If the error changes over the range you can have a lookup table and subtract different values according to the reading.

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Rob


Sir thanks for your help. I really appreciate it.

I'll just match the reading of my device from a digital room thermometer to tell in my data gathering that it is accurate. Is it ok if i do that?

wildbill

Yes, and no. Do you have any reason to think that your digital thermometer is accurate? Your only options, as already discussed are to get an accurate thermometer to calibrate against, or use some other known temp e.g. freezing & boiling (adjusted for altitude) water. Having said that, for your purposes, does it actually matter if your measurements are a degree or two off? For minimizing power consumption of course, perhaps it does.

It's the classic problem of telling time with two watches - how do you know if either is right?

janno0718


Yes, and no. Do you have any reason to think that your digital thermometer is accurate? Your only options, as already discussed are to get an accurate thermometer to calibrate against, or use some other known temp e.g. freezing & boiling (adjusted for altitude) water. Having said that, for your purposes, does it actually matter if your measurements are a degree or two off? For minimizing power consumption of course, perhaps it does.

It's the classic problem of telling time with two watches - how do you know if either is right?


Maybe using freezing or boiling water is a good option for me. But i also need a temperature measurement that will test my Fan Speed. Which is temperature between 13 and 23


wildbill

Just fake it - hard code the test temperature you want in the code to overwrite what you're getting from the sensor. If you want to get a little more sophisticated, wire up a button or buttons so you can increment/decrement the faked value.

janno0718


Just fake it - hard code the test temperature you want in the code to overwrite what you're getting from the sensor. If you want to get a little more sophisticated, wire up a button or buttons so you can increment/decrement the faked value.


Mmmhh... I also need to test my device when i'm presenting it in my panels. Therefore, I cannot change the code while presenting it. All i need to do is make a temperature which is between the range that I need. But the only problem is I dont know how. xD

wildbill

How about giving the system a calibration option then? Use another variable to store the calibration offset and use the buttons to inc/dec it. Display sensor temp and adjusted temp (sensor+offset) on your LCD. Make your fan output decisions based on adjusted temp. For testing you can use the buttons to move the adjusted temp through the range desired to show how the fan activity varies. If you ever get an accurate thermometer, you can use the calibration function to adjust if necessary. Store the offset in EEPROM when you change it and load it on power up.

janno0718


How about giving the system a calibration option then? Use another variable to store the calibration offset and use the buttons to inc/dec it. Display sensor temp and adjusted temp (sensor+offset) on your LCD. Make your fan output decisions based on adjusted temp. For testing you can use the buttons to move the adjusted temp through the range desired to show how the fan activity varies. If you ever get an accurate thermometer, you can use the calibration function to adjust if necessary. Store the offset in EEPROM when you change it and load it on power up.


Excuse me. You have a good idea. And i think I will do that. But i have a question. How can I store the offset in EEPROM?

wildbill


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