Logger sensor range and accuracy

[Steve Chamberlin]

John (EBo) asked a question about the logger's accuracy in email, which I'll answer here.

The range and accuracy of the BMP085 sensor exceed what you actually see in the Logger UI, because the software effectively throws away some digits to the right of the decimal point. This was an intentional choice in order to reduce the number of bytes per sample, so more samples could be stored in EEPROM memory. If you want full resolution or greater range you could certainly have it, albeit with fewer samples able to fit in memory. Or maybe you could brew up some kind of in-memory compression.

Here's the datasheet for the BMP085: http://www.bosch-sensortec.com/content/language1/downloads/BMP085_DataSheet_Rev.1.0_01July2008.pdf

summary of the BMP085 specs:

  temperature from -40 to +85C with 0.1C resolution, absolute accuracy +/-0.5C at 25C

  pressure from 300 to 1100 hPa (+9000m to -500m altitude) with 0.01 hPa resolution, relative accuracy +/-0.2 hPa, absolute accuracy +/-1.0 hPa, at 25C

  

[EBo]

On Mon, 17 Oct 2011 21:30:19 -0700, Steve Chamberlin wrote:
> John (EBo) asked a question about the logger's accuracy in email,
> which I'll answer here.
>

> ...

>
> summary of the BMP085 specs:
> temperature from -40 to +85C with 0.1C resolution, absolute
> accuracy +/-0.5C at 25C
> pressure from 300 to 1100 hPa (+9000m to -500m altitude) with 0.01
> hPa resolution, relative accuracy +/-0.2 hPa, absolute accuracy
> +/-1.0
> hPa, at 25C

The pressure is likely more bits than I need, and 0.1C resolution with
+/-0.5C at 25C is close to what I had specked out for my application
originally. Thanks for clarifying this.