HDC1080: Sudden differential temperature in the temperature rise test phenomenon

Howdy kyt,

After some further study, it looks like you may be referring to a TI developed SensorTag. I've been unsuccessful in finding the tag that includes the HDC1080 device, may I know the full name or description of the SensorTag? A 5 degree delta in ambient temperature is quite large, which leads me to the conclusion of a defective Tag, or we may need to study the issue more to understand the root cause. Please let me know if you have any questions, and I look forward to your reply.

Best Regards,
Matt

Matt,

thank you for your reply.

I miss to post device name.

the correct device is HDC100(NRND) on the CC2650STK.

regards,

kyt 

Howdy Kty,

Thanks for the information regarding the device and sensortag name.  To better understand the issue you're currently facing, can you provide data that you are obtaining from the device.  Additionally, please ensure that the window to the sensor is not obstructed, as this would result in inaccurate ambient temperature reading. 

Best Regards,

Matt

Hello there,

I also encountered some problems with the humidity senbsor of the CC2650STK sensor tag.

As you can see in the picture, the sensor starts to act strange and generates spikes after some time. This is already my second tag I with which I got this behavior. The android app just shows either 0 % humidty or 100 %. 

Also the temperature from this sensor is completely off:

2018-02-27_08:39:05 (-40.0, 99.99847412109375)
2018-02-27_08:40:06 (17.91717529296875, 30.615234375)
2018-02-27_08:41:07 (-40.0, 99.99847412109375)
2018-02-27_08:42:08 (17.07122802734375, 27.03857421875)
2018-02-27_08:43:12 (-40.0, 99.99847412109375)

Since the tag is placed on my bookshelf in my living room, it is not placed in a harsh environement or in the direct sun. ...

Do you have any idea how to not get this problem? 

BTW sorry for this quick and dirty picture. 

Howdy user5265586,

This is indeed a strange issue.  Can you confirm that the sensor tag is not in the path that would cause any temperature variations, such as vents, fans, etc?  Relative humidity calculations are dependent on temperature information, therefore you will need to verify that the temperature value stabilizes.  The sensor tag includes windows that allow the environmental ambient temperature and humidity to expose the sensor.  Can you verify that these windows are not obstructed?  Additionally, please ensure that no contaminants enter the window as this would corrupt the exposed HDC sensor, and produce erroneous results.

Best Regards,

Matt

Hody MAtt,

Yes I can confirm, the sensortag is completely free of contaminations or what so ever. I also placed it at different spots in the room and got this problem again. I think the sensor is broken. My concern is, that this is already the second one in less than 8 weeks.

Cheers,

Chris

Hi Chris,

Is the above issue intermittent or random? Can you provide more samples/data of a capture? The graph along with your responses may indicate a communication problem, can you verify that the device is not placed near any components or systems that may be producing EMI?

Answers to these questions will be helpful in our debug efforts.

Best Regards,
Matt

Hi Matt,

It is at first random and gets more and more intermittent. If it is a communication problem, then it is on the board, the other sensors are working perfectly.

I moved the sensor around in the room and got the same problem, so maybe the defect gets triggered by BMI but then persists. Other data just looks the same way, no information there. There is no error message or so. Unfortunately I don't have the dev-board, maybe this would give some extra traces.

Is it possible, that this behavior can be triggered by a certain amount of sensor readouts over a long time?

Best regards,

Christoph

Hi Matt,
The sensortag is placed on my office desk, so I don't think it gets high temperatures or high doses of UV light. I'm still breathing so it can't be that toxic.
Best Regards,
Chris