between 13 and 19
Quotebetween 13 and 19I 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.______Rob
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
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?
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.
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.