I like your sign–that probably helps get the word out about the importance of your study and helps to prevent interference. I made one, too, I plan on placing one at both the ambient plot and the warming chamber plot. Here’s what mine looks like:
I laminated the sign and then used some serious tape to get it on the chambers. Kids had to tell me the best places to place them, mainly because when I asked their opinion about a few places they told me, “No Mrs. Smith, people will pee on them there.” Cracked me up, but I took their advice.