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HDC2080: The accuracy of rH and temperature while using HDC2080

Amit Shrivastava66
Prodigy 30 points
Part Number: HDC2080

Hello TI,

As per datasheet HDC2080 sensor is factory calibrated to rH accuracy of ±2% and temperature accuracy of ±0.2°C.

But we are not getting the accuracy as mention in datasheet. The results we are getting, are varying up to ±10% in rH and ±4°C in temperature.

I need to know :-

1. As per datasheet HDC2080 have the accuracy of ± 2% in rH and ±0.2°C in temperature then what is the significance of rH and temperature offset concept of up to ±25 % in rH and ±20.62 °C in temperature.


2. If the HDC2080 have the accuracy of ±2% in rH and ±0.2 °C in temperature then what is the need of offset.


3. The accuracy as you are mention in datasheet is with offset or without offset?

  • 0
    TI__Guru* 91206 points

    Dear Amit - 

    You are correct - the parts as shipped, should follow the datasheet spec.with offset registers 0x08 and 0x09 at default values of 0x00, 0x00. 

    The value of +10% on RH that you are seeing - 

    1. is the temp reported from HDC low or correct? (if low, this would elevate the reported %RH value from the device)

    2. what were the handling procedures after soldering? Did you use 'no-clean' flux? Did you wash the boards?

    3. do you have a temp only chamber in which you could put a couple units @ 100C for 10-12 hours and then check them again? 

    For your questions 1, 2 & 3: 

    The offset registers are available for fine tuning (to get under +/-2%) and/or tracking a known reference. I have used them with dew point mirror, taken data over range, determined point to point and average offsets that could be applied and seen that i can closely track in that manner. This would be applicable for folks who have the time in their manufacturing flow (not everyone does) and need the 'extra' precision to go along with the accuracy of the device and do this perhaps for each unit or lot of their products. These registers are also available for correcting any longer term drift that may occur as a result of natural aging of the polymer. This of course implies that the developer plans for this ahead of time - either by storing initial values captured when in a known environment (like final test), comparing at specific time intervals and adjusting as necessary and or if on a 'connected' device doing initial reads at install, storing in the cloud, then periodically having the cloud service check on it  and update as necessary. The other reasons for the offset registers are to handle extreme conditions - for example, in certain product qualifications, for stress testing, folks expose the parts to high temp and high humidity for extended periods of time (a scenario that most likely would never occur in typical consumer or industrial end products) . This is a known condition which causes offset to occur, For their testing purposes, offset registers are there to allow them to characterize their systems, apply offsets if desired, and get readings back to normal levels. Their also might be instances where the end equipment is exposed to a VOC,  -  in fact, different VOCs affect the polymer in different ways - we have seen this in exposure testing, and when this occurs, if access to a chamber to bake the VOC out of the units is not possible (i.e. already deployed), using the heater for extended period of time is not an option (i.e. battery operated equipment), then offset could be applied to recover.  

    For the temp offset - it exists to help out when self heating is occurring. This happens with less than optimal layouts and is described in the datasheet and an app note which covers optimization and placement. When this happens, the temp sensor will be reporting a higher temp than ambient and the humidity result will be lower than it is supposed to be as well (this is because the temp is used to calculate the humidity and they have an inverse relationship mathematically)

    To be clear, the offset registers were designed as a convenient feature to use if you need to, not a one that is required, except as mentioned above.