"Temperature monitoring threshold less than 0 degree C is not supported for DS18B20"

[Cynog Rhys]

Anyone else getting this message when trying to calibrate ?

This temp sensor is also drifting quite a lot, the bath temp is 20.1deg C this morning but the sensor says 24deg C.

We only receive it on one sensor at this time, but it did appear last week on another.

Any Info appreciated 

[Zhiheng Cao]

We do not sell DS18B20 water proof temperature probe, any accuracy issue with this probe is responsibility of the vendor from whom you bought this probe (there are many different vendor/versions of this commonly available temperature probe)

When you try to calibrate, your monitoring threshold is re-applied based on the new calibration. If as a result the threshold is <0C error is generated. For example if your original threshold is 5C, reading without calibration is 10C, you calibrate it to 20C, as a result the threshold applied to device (without calibration) becomes -5C resulting in this error. 

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[Phil Gardner]

So how to fix the problem?  or work around the problem?

[david hotvet]

I have had those issues as well. I have 4 units with external sensors. Have tried swapping them out and they all apparently have similar issues. Below is a picture of the ones in question.

On Wednesday, July 29, 2015 at 8:12:51 PM UTC-5, Phil Gardner wrote:

So how to fix the problem?  or work around the problem?

On Wednesday, April 29, 2015 at 9:21:00 AM UTC-7, mytaglist.com support wrote:

We do not sell DS18B20 water proof temperature probe, any accuracy issue with this probe is responsibility of the vendor from whom you bought this probe (there are many different vendor/versions of this commonly available temperature probe)

When you try to calibrate, your monitoring threshold is re-applied based on the new calibration. If as a result the threshold is <0C error is generated. For example if your original threshold is 5C, reading without calibration is 10C, you calibrate it to 20C, as a result the threshold applied to device (without calibration) becomes -5C resulting in this error. 

On Wed, Apr 29, 2015 at 12:03 AM, Cynog Rhys <cyno...@gmail.com> wrote:

Anyone else getting this message when trying to calibrate ?

This temp sensor is also drifting quite a lot, the bath temp is 20.1deg C this morning but the sensor says 24deg C.

We only receive it on one sensor at this time, but it did appear last week on another.

Any Info appreciated 

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[Zhiheng Cao]

We know some DS18B20 probes are very bad quality. I had this problem (temperature reading jumping in steps) with a DS18B20 I bought from Amazon really cheap. 

I bought another one from Amazon from a different seller and that one did not have this problem.

 

I suspected some bit error when the data is transmitted from the probe to the Reed sensor, but that should generate a reading that is off from the right value by 2^x degrees C 

(the DS18B20 outputs 16bits data and the upper 8bit has unit of exactly 1 degree C). I found that it was not the case. When this happened, the reading was off from the right value by 

something would require most bits in the output to be flipped. And the error step was not always the same.  

On Wed, Sep 9, 2015 at 8:00 PM, david hotvet <daho...@gmail.com> wrote:

I have had those issues as well. I have 4 units with external sensors. Have tried swapping them out and they all apparently have similar issues. Below is a picture of the ones in question.

On Wednesday, July 29, 2015 at 8:12:51 PM UTC-5, Phil Gardner wrote:

So how to fix the problem?  or work around the problem?

On Wednesday, April 29, 2015 at 9:21:00 AM UTC-7, mytaglist.com support wrote:

We do not sell DS18B20 water proof temperature probe, any accuracy issue with this probe is responsibility of the vendor from whom you bought this probe (there are many different vendor/versions of this commonly available temperature probe)

When you try to calibrate, your monitoring threshold is re-applied based on the new calibration. If as a result the threshold is <0C error is generated. For example if your original threshold is 5C, reading without calibration is 10C, you calibrate it to 20C, as a result the threshold applied to device (without calibration) becomes -5C resulting in this error. 

On Wed, Apr 29, 2015 at 12:03 AM, Cynog Rhys <cyno...@gmail.com> wrote:

Anyone else getting this message when trying to calibrate ?

This temp sensor is also drifting quite a lot, the bath temp is 20.1deg C this morning but the sensor says 24deg C.

We only receive it on one sensor at this time, but it did appear last week on another.

Any Info appreciated 

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[david hotvet]

Thanks for the info. I ordered a batch of 10 that were very inexpensive, although they had good reviews :(. Have chosen a separate vendor with better reviews and will see how they work.

On Thursday, September 10, 2015 at 10:38:52 AM UTC-5, mytaglist.com support wrote:

We know some DS18B20 probes are very bad quality. I had this problem (temperature reading jumping in steps) with a DS18B20 I bought from Amazon really cheap. 

I bought another one from Amazon from a different seller and that one did not have this problem.

 

I suspected some bit error when the data is transmitted from the probe to the Reed sensor, but that should generate a reading that is off from the right value by 2^x degrees C 

(the DS18B20 outputs 16bits data and the upper 8bit has unit of exactly 1 degree C). I found that it was not the case. When this happened, the reading was off from the right value by 

something would require most bits in the output to be flipped. And the error step was not always the same.  

On Wed, Sep 9, 2015 at 8:00 PM, david hotvet <daho...@gmail.com> wrote:

I have had those issues as well. I have 4 units with external sensors. Have tried swapping them out and they all apparently have similar issues. Below is a picture of the ones in question.

On Wednesday, July 29, 2015 at 8:12:51 PM UTC-5, Phil Gardner wrote:

So how to fix the problem?  or work around the problem?

On Wednesday, April 29, 2015 at 9:21:00 AM UTC-7, mytaglist.com support wrote:

We do not sell DS18B20 water proof temperature probe, any accuracy issue with this probe is responsibility of the vendor from whom you bought this probe (there are many different vendor/versions of this commonly available temperature probe)

When you try to calibrate, your monitoring threshold is re-applied based on the new calibration. If as a result the threshold is <0C error is generated. For example if your original threshold is 5C, reading without calibration is 10C, you calibrate it to 20C, as a result the threshold applied to device (without calibration) becomes -5C resulting in this error. 

On Wed, Apr 29, 2015 at 12:03 AM, Cynog Rhys <cyno...@gmail.com> wrote:

Anyone else getting this message when trying to calibrate ?

This temp sensor is also drifting quite a lot, the bath temp is 20.1deg C this morning but the sensor says 24deg C.

We only receive it on one sensor at this time, but it did appear last week on another.

Any Info appreciated 

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