For the last few days the analysis of my temperature reading showed it as being high compared to nearby stations.\u00a0 Sigh, here we go again.\u00a0 I’d been watching the temperature readings along with neighboring stations on Weather Underground and had come to suspect my readings.\u00a0 So I started doing some investigating to find whether I had a problem or not.<\/p>\n
First I opened up the FARS to have a look inside and make sure everything was OK and still in place.\u00a0 I didn’t find any problems there.\u00a0 My humidity sensor has a thermometer in it that isn’t as accurate as my main temperature sensor but could be used for comparison.\u00a0 It agreed with my temperature sensor, so I was able to rule out a sensor malfunction.\u00a0 I have another digital thermometer located in another part of my yard.\u00a0 It was reading several degrees lower than the weather station.\u00a0 So I knew I had some kind of problem inside the FARS housing.<\/p>\n
Since I had some problems in the past with a voltage regulator getting slightly warm on my temperature board, I removed the jumper that supplied power to that regulator.\u00a0 It is only used to supply external power for the 1-Wire sensors and isn’t strictly necessary since the sensor can run using parasitic power.\u00a0 I waited and watched the temperature readings, but they didn’t change.\u00a0 So now I need to put the jumper back on the board.\u00a0 Oh well, no rush.\u00a0 It seems to be reading fine using passive power for now.<\/p>\n
I thought I might still have a problem with the fan in my FARS generating some heat.\u00a0 I tried adding a potentiometer outside of the housing to slow the fan down, but that didn’t seem to help.\u00a0 I had also tried just disconnecting the fan altogether, but I wasn’t certain that was the problem or not.\u00a0 In testing i had done in the past it had appeared to be working the same regardless of whether the fan was plugged in or not.\u00a0 After giving it some more thought, I decided to turn off the fan again and observe the behavior.\u00a0 .If I was right about the fan causing some heating, the expected behavior would be a spike in temperature immediately after shutting off the fan due to the heat generated by the motor not being evacuated from the housing by the fan.\u00a0 Then as the fan cooled off I should see the temperature fall to match the neighboring weather stations and my digital thermometer.\u00a0 This wasn’t what I had observed the last time I tried, but this time the fan really looked like the most likely culprit.<\/p>\n
I unplugged the fan and left for work.\u00a0 Later in the day I checked the graphs from my station and saw a spike in temperature just after I unplugged the fan, then a gradual fall in temperature.\u00a0 Eventually the temperature dropped to where the daytime temperature from my station more or less agreed with the neighboring stations. The nighttime temperature was significantly lower than most of the neighboring stations except for one.\u00a0 But it also agreed with my spare digital thermometer.<\/p>\n
Looks like my fan heating theory was correct.\u00a0 I’ve left the fan disconnected for now.\u00a0 This means I will probably get some solar heating in the morning when the sun shines on the housing.\u00a0 I can live with that for now.\u00a0 And I plan to order another fan in the next few days for installation next weekend.\u00a0 Tine to hit the catalogs and research fans.<\/p>\n","protected":false},"excerpt":{"rendered":"
For the last few days the analysis of my temperature reading showed it as being high compared to nearby stations.\u00a0 Sigh, here we go again.\u00a0 I’d been watching the temperature readings along with neighboring stations on Weather Underground and had … Continue reading