Temperature Sensors: Difference of 2° Philips Hue Sensor vs. Fibaro FGMS001

Hardware Home Automation
1

i have gotten both of them and put them on the same spot in the living room
out of interest i checked the temperatures, to see if they measure (almost) the same - but i have a difference of 2° Celsius. Same spot, same room.

any ideas? do i really need a third to get a hint if one is broken?

2

I don’t think that one of them is broken. every sensor has a tolerance. If this tolerance is ± 1° your 2° are in range. You should check what the tolerances are.

For the fibaror i found the information that it has a tolerance og 0,5° in the range from 0° to 40°. For the Huw sensor i didn’t find any information

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Hi Marc,

I am experiencing the same for all of my Philips Hue Motion Sensors.

Maybe you are interested in using the Offset Profile provided by the framework to adjust the value.

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It is a general problem with the Philips Hue motion sensor. If you google it, you´ll notice quite a few topics about the motion sensor beeing 2 degrees celsius wrong. There is nothing to do than to live with it, as far as I know, or use a openhab rule to make a “software” calibration.

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thanks @cweitkamp, that could be a way to go - then i would need a device (a third sensor, but which?!) to get the real calibrated temperature.

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Something like these:
image
They are normally quite accurate and can be used for this type of electronic calibration

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omg :smiley: ofc youre right, it shouldnt be hard to get a officially calibrated thermometer somewhere.
at leas mum and dad will have one :smiley:

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It’s actually not that easy to find and not cheap either.
What you can do is calibrate your own temperature probe:
Get one of these:
image
Food temperature probe

Then calibrate
I a bowl full of water AND ice, wait 1/2 hour for temperature to settle.
The temperature should be EXACTLY 0°C on your probe

Then put a pan of water for boiling and boil away. When the water is really boiling hard, the probe should show 100°C

When you have done this you have a calibrated probe.

In the UK, food outlets are required to do this once a week at least and get their probes lab calibrated once a year. When I was in the restaurant industry, we used to do this weekly to calibrate our probes.

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oh, nice tip - i have a food probe for my grill.
will try this and get back with the results. thanks @vzorglub

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Vincent. Though it may work for most of us, it isn´t quite enough for a real calibration…

First, you´ll need a thermometer/measure instrument where you can change the offset… (dont know if the food temperature probe you showed can do this). If you cant change the offset, then you´ll only be able to notice the differences between your bowl of water with ice, and the measuring. The same with the boilded water.
(Btw. boild water dont always reach 100 degree celcius. So this is infact not such a good idea to use boilded water. Water can boild at 92 to 98 degree celcius. Its all a matter of whats in the water (calcium, salt etc), and the pressure under which the water boils).

It is actually high difficult to calibrate temperature. You have to have at least one reference to measure your offset from. Which means you have to have something which you know for sure is 100% correct. Neither ice water or boild water can do this.

In the industry sector, calibration would probably be using a smaller range than 0 - 100 degree celcius. Ie, if you need temperature about human body (37 degree celcius) you would probably calibrate somewhere between min/max, like 25 - 45 degree celcius. Most human would be dead reaching outside this range, and by then, there is no need to measure at all :slight_smile:

For calibration our temperature sensors, I can only advice to get the very best temperature probe/measuring instrument you can afford.
Make sure to get one which has been calibrated close to the range you´re suppose to use it.
Then trust it and do the calibration from that one only.
If you change reference, you´ll need to start all over calibrating all sensors again.
Always remember to let the reference instrument settle every time if has been moved from one location to another (one room to another).

Another advice could be to use 2 or 3 references, and then use the average temperature as reference. This is what I did with my 12 room temperature sensors, cause I was to cheap to buy a good reference :slight_smile: It took almost a day to get through :frowning:

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