[Derek]

Hi
I am using software version 4.1 b006 on a Pro2 plus.

My SHT21 outside sensor is showing a temperature that is about 2 degrees C  above surrounding weather stations.
I have tested this with an accurate thermometer to verify its higher.
I would like it to be more accurate when the temperature is fairly near zero, as it is now.
At higher temperatures it would not matter to me being a couple of degrees higher.
Is there a way to adjust this in the software.
I have looked, but can not see how or if its possible.
I use Weatherduino to upload to the Weather underground.

Regards Derek

[hornychz]

Hi Derek,

This is very strange. Personally, I would not want to set up the software but I would rather be interested in the sensor itself. I.e:
1) is the sensor itself ok? - I'd try to replace them ...
2) is a good quality radiation shield?, it works properly its forced ventilation?, are properly set ventilation conditions?, etc ...

Good luck

[Derek]

Hi Derek,

This is very strange. Personally, I would not want to set up the software but I would rather be interested in the sensor itself. I.e:
1) is the sensor itself ok? - I'd try to replace them ...
2) is a good quality radiation shield?, it works properly its forced ventilation?, are properly set ventilation conditions?, etc ...

Good luck

Hi Zdenek

Thank you for your reply.
This is my 3rd sensor, the last 2 both gave me humidity readings that were always near 100%
This sensor seems ok on humidity but is out on temperature.
I had not noticed it before the weather dropped down to near zero.
That's why I compared it with a couple of different thermometers.
Its always in the shade and is in the centre of an old Maplin shield I fitted with a fan.
I was rather hoping that there might have been an offset setting I had missed in the software.
Perhaps I might be better off getting a couple more sensors to try.
A last resort would be to use the offset in Cumulus to correct the reading, but I would rather
get it right with the Weatherduino and continue to use that to upload to the Weather Underground.

Regards Derek

[hornychz]

Hi Derek,

This is very strange. Personally, I would not want to set up the software but I would rather be interested in the sensor itself. I.e:
1) is the sensor itself ok? - I'd try to replace them ...
2) is a good quality radiation shield?, it works properly its forced ventilation?, are properly set ventilation conditions?, etc ...

Good luck

Hi Zdenek

Thank you for your reply.
This is my 3rd sensor, the last 2 both gave me humidity readings that were always near 100%
This sensor seems ok on humidity but is out on temperature.
I had not noticed it before the weather dropped down to near zero.
That's why I compared it with a couple of different thermometers.
Its always in the shade and is in the centre of an old Maplin shield I fitted with a fan.
I was rather hoping that there might have been an offset setting I had missed in the software.
Perhaps I might be better off getting a couple more sensors to try.
A last resort would be to use the offset in Cumulus to correct the reading, but I would rather
get it right with the Weatherduino and continue to use that to upload to the Weather Underground.

Regards Derek

Hi,

Perhaps it would potentially be possible to hit the code in the RX_TX.ino file, but I would really try
to avoid it at all costs. Not only will you have trouble with each upgrade but you never know how
the code will evolve in the future and what you can do.

By the way, have you tried SHT31 already?

[werk_ag]

Hi Derek,

I completely agree with Zdenek about avoid of doing temperature compensation of the software, especially for the outdoor temperature sensor, our efforts should be focused in trying to get the most precise reading directly from the sensor.
Obviously that its possible to add a fixed offset (that option is available for the indoor temperature sensor), however doing it for the outdoor sensor in the RX software is not so simple, and will require a lot of changes on the code. The easier and more reliable way to do it, is by editing the TX software, and adding a fixed amount (positive or negative) to the reading of the sensor.

Since you are using an SHT21, you can try this in your TX the software. Search for this code:

Code:

// -----  Read temperature from SHT21 (in celsius) -------
void read_SHT21()
{
  T_ExtS0 = SHT2x.GetTemperature() * 100.0;
  H_ExtS0 = SHT2x.GetHumidity() * 100.0;
}

and change to:

Code:

// -----  Read temperature from SHT21 (in celsius) -------
void read_SHT21()
{
  T_ExtS0 = (SHT2x.GetTemperature() + YOUR OFFSET IN DEGREES CELSIUS) * 100.0;
  H_ExtS0 = SHT2x.GetHumidity() * 100.0;
}

I'm suggesting this without having tested it, but it should work.

[f4aii]

I have the same problem and for several months, I modified the code to adjust the value. You have to go to the tab "routines" line 10.

[Derek]

Hi Derek,

I completely agree with Zdenek about avoid of doing temperature compensation of the software, especially for the outdoor temperature sensor, our efforts should be focused in trying to get the most precise reading directly from the sensor.
Obviously that its possible to add a fixed offset (that option is available for the indoor temperature sensor), however doing it for the outdoor sensor in the RX software is not so simple, and will require a lot of changes on the code. The easier and more reliable way to do it, is by editing the TX software, and adding a fixed amount (positive or negative) to the reading of the sensor.

Since you are using an SHT21, you can try this in your TX the software. Search for this code:

Code:

// -----  Read temperature from SHT21 (in celsius) -------
void read_SHT21()
{
 T_ExtS0 = SHT2x.GetTemperature() * 100.0;
 H_ExtS0 = SHT2x.GetHumidity() * 100.0;
}

and change to:

Code:

// -----  Read temperature from SHT21 (in celsius) -------
void read_SHT21()
{
 T_ExtS0 = (SHT2x.GetTemperature() + YOUR OFFSET IN DEGREES CELSIUS) * 100.0;
 H_ExtS0 = SHT2x.GetHumidity() * 100.0;
}

I'm suggesting this without having tested it, but it should work.

Many thanks for advice and info Werk, Zdenek and F4AII
I have now successfully lowered my outside temperature sensor reading.
I have also ordered a SHT31 to try out.
If that is  accurate I will return the code to default.
Best Regards Derek

[hornychz]

Congratulations!