Checking Digital Thermostatat Inside Temperature

[Jim Yanik]

Art Todesco wrote in news:ycdIk.3117$ [e-mail]:

most electronic thermostats use thermistors. about the size of a small seed.

[Wayne Boatwright]

On Sat 11 Oct 2008 05:57:08p, allanc told us...

That sort is a heat sensitive liquid crystal, but I can't remember the name of it. Those with associated electronics will read a discrete digit, e.g.,

72 or 73 or 74.

[Steve Barker DLT]

the actual temp is some thing about 68 to 71.

s

[jmeehan]

Who cares what the numbers are? The *right* temperature is the one that makes you comfortable. Somehow the numbers seem to have become more important than the real goal.

Different places in your home will vary more than that.

[Edwin Pawlowski]

Best is to get a few more thermometers. Then go for five out of seven matches.

Of course, the actual temperature of the 68 and 69 may be 67.9 and 68.6 rounded off.

[ransley]

I have calbirated units, I must because the city can fine me for not supplying tenents with enough heat. You need a marked calibrated glass mercury or liqued filled thermometer, heating supply places have them but call first or go online to like Granger. I have tried the ice method but its not easy to get it exactly. Then I buy thermometers I can adjust or slide up or down the thermometer in its casing. You can then adjust the digital to match. 1 degree is important to me since I pay thousands a month in Ng, tennants lie and say they are always cold, I just had one couple say they were cold when it was 74 in his apt and he had his T shirt on. They proceeded to run their electric heater to keep the place 79, ran up a 800$ electric bill, moved and stiffed everyone. 1 degree makes a difference in my gas bill. Stores sell uncalibrated humidistates and thermometers.

[allanc]

I think that the analytical side of me is taking over. I thought (obviously incorrectly) that a digital thermostat (or thermometer) manufacturered fairly recently should be 'calibrated' out of the box to about +/- .5 or so. As a result, I was unpleasantly surprised when the thermostat and 2 digital thermometers were so far apart.

[allanc]

That is how I used to shop for thermometers with red liquid years ago.

A normal topic of conversation here (southern Ontario) is 'what setting are you using for your furnace (or air conditioner)?' That seems kind of irrelevant now in terms of what we are all posting about here.

[allanc]

Adjust the digital? Do you mean determine that 74 on the calibrated thermometer is 72 on the thermostat, and then set the later to 72? or actually *adjust* the inside temp of the thermostat to a true 72 (using the thermometer)?

[Charlie]

One of the digital thermometers ranges from about 66->86. I do not know about the other. Are you suggesting that I submerse the other? I have no idea if it is waterproof.

Sorry I was thinking of a glass tube thermometer, that is, an analog device.

The trouble with digital is the rounding error. On analog you might read 70 and a half. But one digital might sense it as 70.45 and report 70 and another might sense 70.55 and report 71.

This is exactly why I bought a glass thermometer just to check my digital thermostat. They are less than $5. Then if you really want to make yourself conused, take the room temperature in various parts of the house.

Charlie

[Ralph Mowery]

I adjust it to the point I feel cool or hot enough. I have access to some devices that are accurate to .01 deg at work and could calibrate my thermostat but it is not worth the trouble.

I had a new heat pump system put in about 2 years ago and found that if I set it to 75 in the summer and 70 in the winter my wife and I are satisfied. I don't really care how hot or cold it is showing on the readout.

[ransley]

Find true temp with a glass analog with scale printed on thermometer, then adjust thermostat to match, there are settings if its a quality unit, digital thermometers usualy cant be adjusted, but some can.

[Ralph Mowery]

And even by doing all that you are only sure of one point. It could still be way off at 70 deg.

He should just put a piece of tape over the readout and set it to the comfort zone.

[Wayne Boatwright]

On Sun 12 Oct 2008 07:52:00a, Ralph Mowery told us...

There are many people with OCDC that don't know it.

[Old and Grunpy]

If you have that accurate thermometer why you posting such ridiculer question the average person do not need that accuracy and if you really want to know use human body thermometer isn't that easy solution. tony

[Dave Martindale]

What's wrong with buying a thermometer?

In general, if you want to measure something, you need some sort of measuring equipment. You have a few options:

1. Buy one, new or used.
2. Pay someone else who has one to make the measurement.
3. Find someone who has the tool but will make the measurement for free.
4. Do without.

For this particular application, you could probably use an electronic digital cooking thermometer. I've seen them for less than $10, and they read to a fraction of a degreee. They're probably not *accurate* to a fraction of a degree, but you can check their calibration yourself and compensate for any error. A mixture of ice and water in a vacuum flask, well stirred, is zero degrees C. Water boiling well at sea level is 100 degrees C (and if you're not at sea level, there are tables that will tell you how much the boiling point is reduced by altitude).

Dave

[Dave Martindale]

Only for thermometers that are intended to be used submerged. I have a number of glass lab thermometers (mercury and alcohol) and at least half of them have a line on the body to mark how far they are supposed to be submerged. The part above that is expected to be in air.

In addition, many bimetal dial thermometers are not waterproof and will be ruined if you submerge them. The bimetal element is only in the lower inch or so of the hollow steel shaft, and that's all that needs to be submerged.

Then there are electronic thermometers that are not waterproof and will be ruined even faster when submerged. In these, the measuring element is a small thermistor bead, and it's at the end of the metal shaft.

Dave

[Dave Martindale]

Does it have patches that change colour to indicate temperature? If so, that's an LCD thermometer, not an electronic digital thermometer, and unlikely to be very accurate.

More likely, the digital thermometers will display fractional degrees. So the one will report 70.5 and the other will report 70.6. It probably won't be *accurate* to 1/10 degree, but have enough precision that you don't have to worry about roundoff error.

Analog glass thermometers have infinite measurement precision (you can use a magnifier to resolve fractions of one scale marking), but their accuracy is not infinite, and depends on manufacturing accuracy. There are accurate and inaccurate digitals, accurate and inaccurate analog thermometers.

Dave

[allanc]

Yes, the patches change colour and I tossed it a couple of days ago.

[allanc]

Do you mean that the digital cooking thermometer has some sort of built in calibrator

*or* I have to obtain one to calibrate the thermometer? If the later, then why not just calibrate the thermostat with the calibrator that I obtain? Haven't you introduced an extra step?