Minder Research TempMinder Wireless Thermometer and Clock

I bought two of these – in the winter I take our picnic coolers and use them for storing a (40-lb.) box of apples and another for potatoes – and I wanted to put these in them to let me know if it is getting close to freezing. Unfortunately, one never did register an outside temperature. It must be a bad transmitter because neither one of the receivers registered. The second one registered the outside temperature on one of the receivers (but not the other) . . . . but once the receiver gets much over ten or twelve feet from the transmitter it loses the signal. I got these because they supposedly have three channels (I got three Acurite thermometers, but all had the same channel so I couldn't tell which cooler temperature I was reading). So, these seem to be no more useful to me than the Acurite units, and I'll be returning them both. Update: I now have three of these, and I just checked all three sensors with brand new batteries, and I get no reading on any of my indoor units. Pushing the channel button makes no difference - I can't even see any number for the channel it is trying to receive. It looks like I have no choice but to junk all three.