My indoor/outdoor thermometer started giving bad outdoor temperatures a few weeks ago. I decided it was time for a new one and was on the lookout for something on sale. At Target they had thermometers on sale. I could get an Oregon Scientific one with a wire outdoor sensor for $8. But for $10.48 they had one (Model RAR188A) with a wireless outdoor sensor (model THN122N) and it let you add two more sensors which is appealing because I’d kind of like to know how hot or cold the the attic gets. So I bought it. It worked fine (though the first one I had was the best because it not only recorded the low and high temperatures, but the *time* those occurred; I haven’t been able to find one like that since). But I wondered about adding sensors. On Amazon they had compatible outdoor sensors (I couldn’t find the same sensor model sold individually, though I did find out that Radio Shack’s thermometers are the same as Oregon Scientific but with a different brand) but they were $20 and more. I thought it would be cheaper just to buy another $10.48 unit just for its outdoor sensor (the sensor has a switch that can be set to Channel 1, 2, or 3). After thinking about it for a day, I went back up to Target and got another one (in metallic blue; they also had iPod mini colors pink and green). But what I didn’t realize at first was that I could use both indoor units to read both sensors. So I put one in the kitchen and one in the bedroom and they both can read outdoor and attic temperatures. Pretty cool.
It wasn’t actually all that cool at first. The new one worked fine, but the one I bought yesterday wasn’t recognizing the new sensor. I tried changing it to Channel 3. It still wouldn’t recognize it. I thought yesterday’s thermometer must not recognize Channels 2 and 3. But I knew the new sensor was working because I could read it on the new thermometer. I put the new sensor right next to the old thermometer thinking it was having a hard time getting acquainted. Nothing. I changed batteries in the sensors. Nothing. So I decided to switch the new sensor to Channel 1 and the old sensor to 2 and see what would happen. Eventually the old thermometer didn’t recognize either one, even when I put the old sensor back on Channel 1. I finally gave up, took the batteries out (it didn’t come with batteries, so they were mine) and put the old one back in the package to return it to Target. But for some reason I decided to try one more time. I put the batteries back in the sensor and then back in the thermometer. It recognized both sensors! Now I looked at the new thermometer and it had stopped recognizing the old sensor. I finally realized that the thermometers only look once for a sensor and then never look again. So the sensors have to be running before you ever put batteries in the thermometer. And if you change the channels, you have to take the batteries back out of the thermometer again. That means you have to enter the time and date all over again, which is why I had avoided taking the batteries out of the thermometer earlier.
It was driving me crazy to have two thermometers that could read three different remote sensors and only have two sensors to read from. So I thought I would go back to Target and pick up a third thermometer just for its sensor. As I was looking through what they had I noticed an even cheaper thermometer (Model RAR601) that included a wireless sensor (THRN122N) that was compatible with my two thermometers so I bought that one for only $4.88. Because that sensor is fixed to only broadcast over Channel 1, I had to change one of the existing sensors to Channel 3 (then reset it, and reset the thermometers), but now I am reading all 3. Oddly the new thermometer isn’t reading its own sensor, but the one on Channel 2 which is in the attic.
My cheapo remote sensor stopped working. I put new batteries in it and it still didn’t work. I even took it apart to see if I could find something wrong and still nothing. I knew it wasn’t working because the LED on it wasn’t even coming on every 30 seconds or a minute like it is supposed to. So I threw it away. The next day I thought I would give it another shot and banged in on the counter a few times before putting batteries in it. It started working again!
Of course it wouldn’t sync up with the other units immediately and I think I realized why. Once a unit detects a signal, it must only listen every 30 seconds. So if you take the batteries out of the sensor, you get the two units out of step (unless you get really lucky; I guess you could get a stopwatch and time it before putting the batteries back in). To get them back in step you have to take the batteries out of the main unit (or hit its reset button) and then enter the time and date again.
Then I realized that the cheapo thermometer will read *any* sensor. It just reads the first one it picks up and then falls into that rhythm. So by taking the batteries out and some trial and error I can have it sync with channel 1, 2, or 3.