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geeji

ACTUAL Resolution of DS18B20 Optional Chip with FGK-101 : 10 or 12 bits ?

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Does anybody know the ACTUAL resolution programmed into the DS18B20 chip when inserted into the ++ZW5++ version of the FGK-101 ?

The resolution of this chip  is programmable at power-on to 9, 10, 11 or 12 bits, giving respectively 0.5, 0.25, 0.125, 0.0625°C increments.

With the pre-ZW5 versions of the FGK-101, the resolution was clearly 12 bits, which happens to be the DS18B20 default resolution at power-on.

 

But using the ++ZW5++ version of the FGK-101, with the SAME Device handler,  I get  DISCONTINUOUS readings, for instance 22.4, 22.8, 23.1, 23.4, 23.8°C, but NEVER values in between, such as 23.5, 23.6, 23.7°C for instance.

This is consistent with a 0.25°C / 10 bits resolution only, which would be a major regression compared to the 12 bits of the pre-ZW5 FGK101+DS18B20.

And AFAIK, there is no customizable parameter which would allow me to force 12 bits resolution back.

 

Note that since all FGK-101 temperature parameters (51, 53, 55, 56) are given with 0.1°C quantum, only a 12 bits resolution is consistent with those parameters.

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Just curious.

 

What is the parameter template you get for the pre-ZW5 FGK10x and ZW5 FGK10x?

 

My understanding is that the parameter template for the two variants of FGK10x should be different and that may also affect how the DS18B20 installed in the FGK10x behaves. If memory serves me well, I think even the pre-ZW5 FGK10x gets two different parameter templates dependent on which HomeCenter Software Version it was included on.

 

Pre-ZW5 FGK10x has these parameter templates:

  • 204 (FGK10x firmware 2.1)
  • 308 (FGK10x firmware 2.5)

ZW5 FGK10x has this parameter template:

  • 711 (FGK10x firmware 3.2)

 

I am asking cause I vividly remembered I posted about some weird behaviour observed for FGK10x with and without DS18B20 on different parameter template versions quite some time back.

Edited by chaicka
Additional Info on Parameter Templates for pre-ZW5 FGK10x

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  • Hi chaicka, thanks for the answer and sorry for the late reply (I forgot to check the "Notify me of replies" option).

    I am not too sure I understand what you mean by "parameter template", I suppose it is the format used to parse the Sensor Multilevel Report answer to the Sensor Multilevel Get command, right ?

    If so, as far as I can tell, it is compliant with the v5 version of the Sensor Multilevel command :

    Please login or register to see this code.

    My ZW5 FGK-101 is 3.2 version (the only one, AFAIK).

    My pre-ZW5 FGK-101 is 2.1.

    Anyway, if the parsing template was wrong, I suppose I would get completely erroneous temperature values, but it is not what I get : I get a stream of credible temperature measurements, but instead of a continuum with 0.1°C spacing, I get gaps  of at least 0.4°C between 2 consecutive values. Which is NOT consistent with a 12 bits resolution (0.0625°C quantum).

     

    But to be fully transparent, although I did use in the past the FGK-101 with a Fibaro HomeCenter, I am now using it on a SmartThings Hub. 

    I suppose Fibaro HomeCenter could use NON standard commands to achieve a different behavior, but even on SmartThings, I was getting the expected DS18B20 behavior with the 2.1 version of the FGK-101+DS18B20 (12 bits resolution), while now with the same Hub I am only getting 10 bits from the ZW5/3.2 version of the FGK-101+DS18B20.

     

    So I believe my first question is : for anybody using the ZW5/3.2 version of the FGK-101+DS18B20 on a Fibaro HomeCenter, are you sure you get the full 12 bits resolution ??

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    Hi! I find this question intriguing, and I'd hook up my logic analyser for you, to see what 1-Wire commands are being sent. But unfortunately I don't own a Gen5 door sensor. I'm just curious, are you unhappy because you expect it to be 12 bit, or is your software in some way sensitive to the difference between 10 and 12 bit?

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  • I use those FGK-101 solely as Internet temperature sensors in 12 apartments of a condominium.

    Although the absolute precision of those DS18B20 is only +/-0.5°C, their RELATIVE precision can be much better (around the 12th bit, which is 0.0625°C).

    And since I am most interested in tracking the evolution with time and outside temperature of the inside apartments temperatures, a 12 bits / 0.0625°C resolution is not a gratuitous luxury, but the minimum resolution needed if you want to display a single decimal point with some level of confidence.

    Interestingly, the FGK-101+DS18B20 returns (Sensor Multilevel Report) the measured temperature value with TWO decimal digits of "accuracy", which even with the full 12 bits of the DS18B20 is overly optimistic...

     

    Edited by geeji

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    Thank you for taking your to explain that. I have a few of those, and one is attached to a Fibaro Universal Binary Sensor. And that modules is in a small enclosure, so I can use it anywhere. It's sort of my universal Z-Wave temp reference device. I compare the output to a Fluke 51 k-type thermocouple and a special alcohol thermometer with 0.2 °C resolution. So I can say they agree (at room temperature) to within +/- 0.2 °C celsius. An if allow for some guesswork, I'd say its even within +/- 0.1°C. So I come to the same conclusion that they are very accurate (absolute and relative, in my case) and I've never thought of it as being "12-bit". Now this has been confirmed ;-)

     

    Is it possible that something's odd about your newer DS18B20? Let me say... I've heard rumours that those Aliexpress and Ebay versions aren't "genuine". :-) I'm not saying you're using one of those, and I'm not saying that they are bad per se. I even have a pack of 5 somewhere, but I haven't tried them yet. But just to eliminate this possibility... Would it be possible for you to swap the temp sensor of an old and a new door sensor?

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  • 51 minutes ago, petergebruers said:

    Would it be possible for you to swap the temp sensor of an old and a new door sensor?

    I thought about that, and already replaced the DS18B20 which was in my ZW5/3.2 FGK-101 by a new one, with no improvement.

    But since I had several of those DS18B20 within the same plastic bag, it could be that both were coming from the same faulty batch, so I agree with you the proper test would be instead to swap it with a "known working" DS18B20 from one of the older 2.1 FGK-101.

    I will do it and let you know.

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    27 minutes ago, geeji said:

    I thought about that, and already replaced the DS18B20 which was in my ZW5/3.2 FGK-101 by a new one, with no improvement.

    But since I had several of those DS18B20 within the same plastic bag, it could be that both were coming from the same faulty batch, so I agree with you the proper test would be instead to swap it with a "known working" DS18B20 from one of the older 2.1 FGK-101.

    I will do it and let you know.

    Super!

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  • UPDATE : the problem appears to be more vicious than a "simple" wrong resolution setting, as I initially suspected : see

    Please login or register to see this link.

    .

    Please switch to

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    if you have any suggestion.

     

    LATEST NEWS : the problem now appears to be a resolution of only 8 bits (+/-1°C) but ONLY when getting a synchronous "Multi Level Sensor Report"  in direct answer to a preceding "Multi Level Sensor Get" query. The A-synchronous "Multi Level Sensor Reports" sent by the FGK-10x whenever the delta variation specified in Parameter #51"Temperature reports threshold" is exceeded are OK.

    Edited by geeji

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