Barometric Sensor

[the_top_pilot]

Lee,

How do you confiqure the Pressure sensors? I use the hobbytronics ones straight out of the packet.

Steve

[Admin]

Lee,

How do you confiqure the Pressure sensors? I use the hobbytronics ones straight out of the packet.

Steve

Hi Steve
When I say configure, I am referring to the software configuration.
There are lots of registers which need to be initialized to certain values during the software startup

Thx
Lee

[DanDare]

I have the HT sensor attached to my PAW unit and the QNH seems to be wandering around from 1027 to 1034

I am between London City and Stansted who are both reporting QNH 1029 on the current TAF

Is anyone else seeing these wandering values on a HT baro board?

I have quite a long ribbon cable attached, I wonder if this might be causing an issue?

[DanDare]

Looks like it might be down to the amt of satellites that can be seen at any one time which is causing the gnss altitude to change?

[Paul_Sengupta]

I think so, I think the calculated QNH relies on the GPS altitude. The GPS altitude with the GPS dongles doesn't seem to be that accurate.

[Admin]

This is correct the QNH is estimated by comparing the GPS Altitude and Barometric Altitude.
So the important figure is actually the Barometric Altitude

[Paul_Sengupta]

Can the browser display be updated to have the barometric pressure displayed in the field as well as what's currently there? Just a thought!

[Admin]

Can the browser display be updated to have the barometric pressure displayed in the field as well as what's currently there? Just a thought!

At the moment it prints the following

Code: [Select]

Pressure Altitude (BMP) | Enabled (Auto) QNH=1025mb QNE=-124ft GNSS=229ft
As already discussed the QNH is estimated based upon the relative GPS/Baro Altitude.
Are you asking for the Barometric pressure from the sensor ?
If so that is not easy, the sensor is modal, and can be configured for Altitude, or Pressure.
So it would need re-initializing and then require settling time to perform the calculations for each reading

so in effect you would need to do the following

Code: [Select]

Initialize for Altitude
Settle ...
Read Altitude
Initialize for Pressure
Settle ...
Read Pressure
That would take quite some time I think, I guess it could be run in a separate thread so as not to impact the main thread.
What is the reasoning behind the question ?

[Paul_Sengupta]

Ok, didn't realise that. I was thinking about just calculating it to display it! 

The thoughts were about having a reference value displayed to avoid confusion with the calculated QNH. Just as a troubleshooting/for interest item.

[rodent0_2]

so far so good with this Ardfruit thing. Fit the gps dongle the other day all worked first time.