For anyone interested, I calibrated the DS18B20 to both extremes of freezing and boiling. It was within .50 so offset it and then calibrated the Pearl. This Pearl is almost perfect...1/10th of a degree low. I'll take that as acceptable tolerance!! 
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The response you received is consistent with my own observations of said Deadband. IOW it's a Placebo Setting. No matter how I set Parm 19, the temperature swing/deadband, for me, is still exactly 1.8 Degrees. This translates to 0.9 Degrees below my Setpoint, and 0.9 Degrees above.
Now to see near 0.1 degree increments while running on Battery only, I have to set a rule to Refresh my thermostat every 5 minutes. For good measure I also have another Refresh Rule when the status changes to better capture the exact temp when heat is satisfied. The log, for me, shows the exact same swing regardless of the Parm 19 setting; 1.8 Degrees.
So, it makes sense to me that for a true 1.0 Degree Deadband, I'd fully expect to see 0.5 Degrees below Setpoint when Heat turns on, and 0.5 Degrees above when Heat turns off. I just don't see it. Does anyone actually have a log that shows a 1.0 degree on/off swing?
Hi,
I've yet to measure the room temperature swing with an external device, however early indications suggest the temperature control for this thermostat is below par. My Honeywell would hold the temperature right at 69 °F. Although the Honeywell would only display temperature in whole degrees F.
I'll report when I finally get to measure the two in the same room with an external thermometer.
John
I know this tread is old, but wanted to post my initial observations about this thing.
I just got it today and have it on the bench and testing it.
I HATE IT!!!!
WHY did they choose a dark blue display?
The whole display is real dark and hard to see (yes I have the brightness set to 99, and on AC power only).
Parameter 09 (not 19) is for the "minimum deadband" and the smallest I can set mine to is 11 (1.1 deg F), NOT 1.0.
The thing is pretty... pretty BAD!
I am expecting a GoControl to test also, but I think this one is going back....
It's funny. I had every reason to hate this, but find it to be just fine in real use.
I took a risk on an open box, because I really wanted the slick black/black model. The one that I received was really white and has one segment of the second character that doesn't illuminate properly. It was clearly played with, as I had to mess with menu settings to connect.
Heck, even the wire connectors were odd to me. The wires need to be at a certain angle, which I did not find intuitive. Maybe it's just me.
A week or so into use, my only complaint is that the previous owners of this house placed the thermostat in a bad spot (near South facing windows). Hysteresis has been a non issue.
That is my story only. I wish you well in finding the right fit for you.
Well I appreciate your thoughts.
I bought one off Amazon that was $25 but NOT open box!... at least it wasn't advertised as being open box, but it really does look and operate like a new one.
Still, I am going to give the GoControl a shot and see which one I prefer.
IF I like the Pearl, I might try opening it and see what can be done to increase the brightness of the display. It (to me) is very dim...
We'll see.
Thank you again!
You might have gotten lucky, but I have never seen a new centralite pearl sold for that price on Amazon, and I’ve ordered several over the last year or so.
They're only $30 directly from Ezlo now, for some reason--and not a bad price on a few other CentraLite products, either:
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Now you tell me 
.
There was a thread a couple of months ago that mentioned a suspect seller on Amazon. Low price and high failure rate for the Pearls. That price sounds suspiciously familiar.
[EDIT: Added link below]
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My mistake.... I paid $30 on Amazon for mine..... STILL am not impressed.
I will try my GoControl that i just got today and see how different it is.
Don't be deceived by the pretty pictures on Amazon and their website...
The display is DIM (dark blue on black background???? what brainchild thought that was a good color choice?)
It is a good looking stat, but the UI leaves alot to be desired.
I just added one of these. First my display is very bright and easy to read...almost too bright.
Now for the other parts...I don't use them. I use this through the built in app "Thermostat Controller" and I HIGHLY recommend this. At this point I really could just mount this anywhere and save wall space because I use a group of temperature sensors throughout the house so that's taken care of. And there is really no reason to walk up to it because all my settings are automated. So for the cost...I found this to be a very good deal... KNOWING that it had some limitations. In my scenario it's working great.
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hhmmm... really?? Almost TOO bright??? even the blue numbers???
Maybe I got a dud?
I do plant to use TC as well... thanks for the tip!
What temp sensors do you use? I would like something that is fairly quick (about 30 sec to 1 min between reports).
I know some of the combo motion/temp/humidity sensors take a while to report their temps, but the fibaro smart Implant is pretty quick and the reporting interval can be set as well as calibrated with the user provided driver.
One thing, so far, I do NOT like about the GoControl is the minimum off time of 5 minutes and the minimum run time of 3 minutes!
If the stat is satisfied and I want to change the heating/cooling setpoint, I have to WAIT for 5 minutes before the HVAC system will come back on!
If I put the stat in test mode, that can be changed, but it displays TEST in the display rather than the setpoints/time....
I guess I am being picky, but it is what I want, and so far things ain't really right for me.
I had a Pearl controlling my heating in my family room, foyer area. I had replaced a non-smart Honeywell.
I don't have formal data but I could not get the Pearl to control nearly as good as the Honeywell.
I ended up selling my Pearl on ebay and purchasing a Honeywell T6 Z-Wave and am very happy.
I use 13 different temp sensors around the house. Some report faster than others but with the balance it all works really well. It's a mix of Iris/Sylvania/Hue. Most of them report on a change in temp of .25c. So it's temp not time.
You know thinking about this...for as cheap as they are...might be worth getting a 2nd one. Wiring the main one in the basement to control the furnace and using the 2nd one as basically a human interface. Then use RM to handle someone walking up and raising or lowering the temp. I'll have to think about that one!
Thanks for the pic. Kinda hard to tell though as how much ambient light is there?
Still looks alot brighter than mine.
I can try and simulate the brightness in your picture to see the difference.
I know some of the temp sensors I have can be set for delta temp reporting and not time, so I will investigate what I have.
Yes... Amazon has a seller that I bought mine from that has them for 29.99 new.
I sort of remember a menu option that would allow you to vary the brightness.
Yes there is, and I have it set to 99 (the highest).
