These come in a number of different types and are capable of being used in to monitor in a number of ways. The great thing about these is that they are completely self contained and once initialised from a PC or Laptop can be left in any location that you wish to monitor.
 

Setting up your device could not be easier, the picture above shows the main software screen. I should add at this point that we use devices that monitor both temperature and Humidity, you can also get a version that does temperature alone.

You can set the unit up to monitor every N seconds and that's pretty much all you need to do other than decide on where you want to put it. Make sure that you carefully mark its position on your baseline plan, its not much use unless you know exactly where you put it.

When you later get back to examine your results you chose the download data option, which does two things saves the data to a text file on your hard drive and also produces the graph, both shown above. These are both from a real haunted location. They are so sensitive that with a bit of experience you can work out when a door has been opened.

The dew point is one of the useful readings. If you have the monitor in an area where a mist has been reported, you can use the dew point to perhaps explain it.

Our main uses for these devices are when we have locked off or remote monitored cameras watching a location or trigger object, this is when this monitor comes right into its own. Just make sure that the camera and monitor clocks are set to the same time.

On the subject of trigger objects we also use another trick to further monitor the location, a pair of mirrors, carefully place you monitor and monitoring video gear and you have the whole thing covered from all angles. Just to make sure a room guardian, an IR intruder detector and you have it bolted down tight.

All you need now is a co-operative spirit entity to drop by.