1 wire temperature sensore offset

[Gast]

Dear,

Due to the fact that I'm renovating, I can only install my 1-wire DS18s20 temperature sensors in the ceiling.
Because heat rises the temperatures I read from my sensors are +/- 2 to 4°C to high.

Between the loxone documentation I found : http://www.loxone.com/nlnl/service/d...orrection.html
But following this gave me a reading of +219°C

How can I change the readout (offset) of the 1-wire sensors so that they are giving me a more correct result?

wkr,
Tom

[Christian Fenzl]

The Loxone example is not thought to be for 1-wire sensors.

In the correction settings use for example following values:
Input value 1 : 24
Display value 1: 22
Input value 2: 14
Display value 2: 12

You can correct the values by measuring the correct temperature in the room.

Regards, Christian

[Gast]

Christian,
Thanks fort the information.
But how do you get these values? what's the theory behind it?
I have about 15 sensors that I need to adjust so I would like to know how to do this correctly.

wkr.
Tom

[K.Clemens]

Most correct way would be using a calibrated thermometer (Mercury or alcohol) and measure the temperature right next to the sensor. Seems a lot of work, but just do several a day. stabilisation is key

[Gast]

K.Clemens, I am indeed thinking about using a calibrated temperature meter. But lets say the sensor is reading 12°C and the calibrated sensor is showing 16.5°C what values do I put in the loxone config?

wkr,
Tom

[K.Clemens]

Don't know it by hart, but as Christian Fenzl stated:

In the correction settings use for example following values:
Input value 1 : 24
Display value 1: 22
Input value 2: 14
Display value 2: 12

Seems that you have to create a linear correction of 2 values. Ideal between 16°C and 30°C or so. Temperatures you will get in your room. But probably the server will extrapolate te values outside your set region.

[Gast]

K.Clemens,

Thanks for the information.
But I'm not making myself clear I guess.

How do you get these values?
Do you calculate these? if so how?

I have about 15 sensors that I need to adjust so I would like to know how to do this correctly.I mean It would be stupid to make a post and ask for 15 adjustments.. I much rather do this myself.
But in order to do this I need to know how ( procedure, calculation, .....)

wkr,
Tom

[Gast]

Hi Tom,

Correction values for the 1 wire temperature sensors work pretty well and I use them on a couple of devices to correct slightly abnormal readings.

For you situation where you have temp sensors in the ceilings, the first thing to do is check them using a calibrated device to make sure that you are getting temperature values that you are happy with. There will always be a couple of point fluctuations, but it should be close enough.

Then, using your calibrated device, put it in the room where you believe the temperature reading will be more accurate. Normally this is around the same height as a light switch. There will be a variance between the reading your are getting from your DS18s20 in the ceiling and the reading from your calibrated sensor at switch level.

Make a note of the temperature variances. I.E if the ceiling is showing 24 degrees Celsius, but the calibrated sensor is showing 21.5, then you have a 2.5 degree variance.

Switch off the heating in that room and let it cool down. Then take readings at a lower temperature. Again, the ceiling temperature is likely to be higher than the switch level temperature. The readings might be something like 15 degrees (ceiling) and 14.1 degrees (switch).

You now have some correction values to work with in Loxone Config.

As the guys have said above, the Input Value is the temperature that is being received from your DS18s20 sensor in the ceiling. The Display Value is the corrected value which should correlate to the actual temperature (at light switch level).

The reason for having 2 Input and Display values is to create a scale in which to make the calibration adjustments.

So in the scenario above, if the ceiling temperature is 15 degrees and the switch level temperature is 14.1 degrees.
And when the heating is on, if the temperature in the Ceiling is 24 degrees and the switch temperature is 21.5 degrees then you would use the settings:

Input Value 1: 15
Display Value 1: 14.1
Input Value 2: 24
Display Value 2: 21.5

This then creates a scale which should provide more accurate actual temperatures for the room.

Hope this makes sense.

Regards,
Gary

[Gast]

Gary,

This is now crystal clear for me !
Thanks very much guys for the info and the patience.

wkr,
Tom