I have three, I bought 2 at ace hardware and one at harbor freight. I like the transmitting type. I can sit in my recliner and know soil temp, temp in the freezer or outside temp. Mine are all cheap units that I bought here and there whenever I would find one on sale.

You can get one with several channels on it to monitor different places, I think one of mine has three channels. I don't remember about the other two units. I only leave one of them in service all the time.

I can look over my left shoulder and see it is 69.4 degrees in the house and 37.4 degrees out side. I don't use the min/max feature a lot, but if it is correct it has been up to 47.3 out side and down to 33.8.

I think the cost runs in the 12 to 20 dollar range.

Most of the stuff I buy is from Amazon, only because of free shipping over $25.00.

Larry

Thanks, Larry, I didn't think of Amazon although I know they sell a lot more than books now. I'll take a look. How far away does the transmitter work? The greenhouse is maybe 300 ft from the house. It would be nice to check the temp out there from the house.

Mine say a range of 100 ft.. I have read of some that will reach 300 ft. or more, but I am sure they cost more than mine. Mine have to have batteries in the sending unit and receiving unit. I expect that all transmitting type are like that.

Another item you may want to think about is "stand alone" thermostat. I think I have three of those also. They don't need a transformer to turn on power. I have one attached to an 18 ft. string of rope lights that only put out about 53 watts of heat, but the two largest will power 1500 watts, maybe more. Mine only hold the temp within +/- 5 degrees, provided you have a large enough heat source to heat the ares. The thermostat is about $15.00, the rope light about 10, of course you can plug any type of 115 volt source into it.

Thanks, Larry. I will show DH your post as he will know more what you are talking about than I do (watts I know, but volts and amps have always confused me.)