[time-nuts] Crude Survey Technique

[Brian Lloyd]

On Sun, Nov 24, 2013 at 7:13 AM, David J Taylor <
david-taylor at blueyonder.co.uk> wrote:

> The Thunderbolt uses single precision floating point and digital filtering
> for temperature so yes, you are going to see values like this. This is not
> unusual (precision clearly out of step with accuracy), like the HP network
> analyzers returning gain in dB with 4 decimals at microwave frequencies.
> Not sure what your point is?
> Should Lady Heather pretend to know better and muck with what's sent by
> the receiver?
> I prefer not but it's a matter of opinion.
>
> Didier KO4BB
> ===============================
>
> Oh, if that's what the Thunderbolt sends, then that's what should be
> reported.  I hadn't appreciated that.  Makes you wonder why the designers
> did that, though.
>

Oh, the answer to that question is easy. They knew that they had to produce
a function to convert 32-bit floating point numbers to decimal
representation in ascii for transmission over the serial port. But it would
require additional code to round off the numbers to desired precision. And
then they would have to decide what the proper resolution should be for
each value. So I would have done the same thing they did.

>
> More modern equipment I've seen uses (for example) integers to report dB x
> 10, so tenths of a dB resolution.  I do see computer temperature sensors
> reporting in millidegrees, with an accuracy of +/-  2°C!
>

Sure the accuracy may be off but if the repeatability is good the high
precision with reduced accuracy is still useful for calculations in a
control loop.

-- 
Brian Lloyd, WB6RQN/J79BPL
706 Flightline Drive
Spring Branch, TX 78070
brian at lloyd.com
+1.916.877.5067