[time-nuts] NEO-M8N vs. NEO-M8T

Gary E. Miller gem at rellim.com
Mon May 21 15:33:46 EDT 2018


Yo Mark!

On Mon, 21 May 2018 19:21:25 +0000
Mark Sims <holrum at hotmail.com> wrote:

> It looks like you have slipped a decimal point somewhere (also that
> "ps" label is wrong).

Yes, seemed 10x too high to me too.  But the doc for UBX-TIM-TP clearly
says 'ps'.

UBX-TIM-TP:
    qErr ps Quantization error of time pulse (not supported
            for the FTS product variant).

Here is another data point, with the raw data so you can check the decode:

Class: TIM(0xd) ID: TP(0x1), len: 0x10
payload: f0fb550900000000e7d6ffffd2070a00
tow:1566300.000000000 qErr:-0.000000105210 ps, week:2002
  flags:0xa refInfo:0x0
      is GPS, UTC available

Sure looks like 105 nano seconds to me.  If I'm wrong I'd love to know
where.

> I have an M8N running here and the report
> sawtooth errors are all within a +/- 10 ns span.   (and LEA-5T is +/-
> 5ns).

Many things could explain the difference.  We seem to only differ by 5x
or 10x.

Also, my ADEV plot clearly showed the NEO-M8N adev was better than the
NEO-M8T adev at tau=0, so your observations match mine.

Right now I'm doing a survey-in.  Then I'll grab a days worth of TICC
data.  After that I'll go back and get long term standard deviations
for qErr in Stationary and Survey-in modes.  That, of course, will take
days.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin
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