Part 1 of 2
We bought our house new. The original thermostat was a Honeywell, LCD variety. The furnace, as we found out last year when we replaced it, was a 120,000 BTU monster. The new furnace is a modest 60,000 BTU. Talk about oversizing, the builder probably bought all the neighbourhood furnaces on an end of year clearance special. The Original thermostat only did Fahrenheit, and the house was comfortable. We had to replace it and the next was a LCD unit again, this time Fahrenheit and Celsius. Being metric here, I switched it to Celsius and immediately, the house was colder. After a couple of weeks, back to Fahrenheit and comfort returned. During all this time I realized that when we had the lights on, candelabra within 8 feet of the thermostat, the house got colder. During the summer, when the lights were on, the house got colder. The first problem of cold was that the Thermostat, operating in Fahrenheit, had finer resolution of control (step) than when operating in Celsius. Our bodies, mine and my family were able to discern a larger difference between heating system on and off when running in Celsius.
Well the thermometer in the photo appears to be Acurate by definition, which is a lot easier than all that calibration stuff! ;)
In a past job, I had to do component measurements at a constant temperature. We used a stirred oil bath, but even with that, it seemed hard to keep the temperature constant. Fun, fun , fun!
70 degrees is a nice temperature, and I've often thought of moving to Santa Barbara, CA to attain it, but if I did I probably wouldn't be able to afford a thermometer.
Funnier and funnier. I like these threads much more than the egomaniacal posturings so typical of many others.
My late mother (whom I hope is enjoying, in some sense, this latest notoriety, as one of her primary complaints was that I never listened to her) said late in life that it was a shame that my father was not still around (left this realm at 77) because finally she wanted things warm, and he had always wanted things on the cool side.
So you know your elevation and you can look up the temperature for boiling there.
Beer is good but I think unreliable and totally unsuitable for boiling!
Nothing is reliable, unless you know how to refer it to a real standard. Your DVM and scope may be pretty good but for example:
- your DVM may drift off cal as years go by
- your scope may also, but at high frequency may suffer from some attenuation - I have seen that fool an engineer.
"Trust but verify."
## If your wife is like mine & having hot flashes.
Oooooohhhh!!! Wait until I tell her that you posted this comment for all to see...
...I know someone who is going to be "singing soprano" in the church choir :-)
##...and boiling water...
But the temperature at which water boils varies as a function of pressure
##...what do you trust?
I trust beer to make me happy :-)
## Do you think your scope and DVM are perfect?
Yes, of course. What? You mean they aren't? Nooooooo... say it is not so!
Since you're married ... couple options.
1) you could say things like "I think you Hot honey!" .... ;^)
2) Some of these "Smart" digital thermostats have background menus. You can change the offset.
3) If your wife is like mine & having hot flashes. Then there is simply no solutions. (other than "yes dear").
There's a good invention ... a thermostat that perceives a wife's desired comfort! I suspect time travel will get discovered first though.
Cheap thermometers are rubbish, because most people don't care anyway. It is worth buying one decent thermometer - my best one is stainless steel electronic but I also have an old mercury one.
You can easily check your best thermometer against ice (everyone has a refrigerator with an ice cube tray!) and boiling water (everyone has a kettle, or at least a stove which you can put a pot of water on) and once you are confident in that, it is easy to compare every other thermometer against it.
This is basic calibration. and the idea and principles should be in every engineers mind. If you can't check your instruments, what do you trust? Do you think your scope and DVM are perfect?
Ah! The innocence of youth... I take it you are not married :-)
On the one hand -- as an engineer I sort of like things to work the way they should ... and this includes having a thermostat (that cost me $175 including installation) that occasionally manages to take a stab at measuring the temperature and gets closer to the real-world value than 4 or 5 degrees...
...on the other hand (and still as an engineer) I agree that a good engineering solution is to just mentally add/subtract the error to whatever the thing displays and have done with it...
... the problem is that my wife is not happy ... she thinks the new thermostat should read the same as the old one (I'm not even going to mention to her that the old one may also have been inaccurate) ... and when my wife is not happy she does not like to suffer "quietly or alone" if you get my drift... (grin)
Much ado about nothing. If you don't want precision temperature measuring devices, just tune the temperature according to the thermostat you have now. At least, you can trust your own sensations. let 74 be the new 70.
Blog Doing Math in FPGAs Tom Burke 24 comments For a recent project, I explored doing "real" (that is, non-integer) math on a Spartan 3 FPGA. FPGAs, by their nature, do integer math. That is, there's no floating-point ...