It may be due to loss of precision in the arithmetic used by Byon and not round off. It could be both. Without seeing the code employed in converting temp input to ascii for embedding in the aprs packet it is hard to tell. I suggest that there is likely an arithmetic algorithm within the microprocessor that would alleviate this. I could help but I don't have the code.
regards rich painter
So it appears the issue was most likely rounding.? Now that the temperature is "significantly below 0" it is displaying as below zero.
Glad it is working!
On Tuesday, July 20, 2021, 9:17:23 PM EDT, py5lf_ < py5lf@...> wrote:
Robert Today morning the temperature reaches negative temperature in Celcius , so my question was answered;
20/07/2021 06:18:02-03:00:?PY5LF-13>APTT4,PP5CRE-15,WIDE1*,WIDE2-1,qAR,PP5APR-10:WX Davis,FTM100DR,5W,GP6,Ext.Temp.:-3C,25F,DGP=OFF
TT4 works very nice !? Thank you? Em qua., 30 de jun. de 2021 ¨¤s 01:06, Rob Giuliano via <kb8rco= [email protected]> escreveu: Wow, what are all those boards in your picture?
As for the negative numbers, that would be a question for Byon.
Going back through the data, the lowest temperature I saw was 30F, which showed as 0C. In theory, this could be resolution and round off error.? I didn't see any temperatures below 30, which would be 'even more negative'.
Do the telemetry parameters match your current telemetry output? Aprs.fi shows your telemetry data as: ?? Power Supply???????? PA
?? Solar Panel P.1?????? SP1
?? Solar Panel P.2?????? SP2
? Battery 1????????????????? B1
? Battery 2????????????????? B2
data with path elements removed???????????????????? PA, SP1,SP2,B1,B2 ,digital
2021-06-29 21:34:13 EDT: >APTT4:T#059,124,000,000,128,127,00000000
2021-06-29 21:38:06 EDT: >APTT4!2529.15S/04913.13WrWX?Davis,FTM100DR,5W,GP6,Ext.Temp.:3C,37F,DGP=OFF
2021-06-29 21:38:30 EDT: >APTT4@.../04913.13W_079/009g015t040r000p018P004h70b10207.DsVP
Just as an experiment, you can try the following settings for telemetry: ??? TELREAD FALSE???????? This will send raw bit values from Analog to digital converter ??? TELHIRES TRUE ? ????? This will? scale the voltage to 0 - 5V will be 0 to 999 counts
??? TELVOLT TRUE??????????? PA will remain TT4 input voltage
??? TELTEMP TRUE?????????? SP1 will be the raw bit value for the temperature sensor ????????????????????????????????????????? The other values will shift right and you will no longer read B2
The millivolt reading is in deg K (x10). So if the analog to digital converter reads about 500, that will be about 2.5V (2500mV)
? to equate to 250 K or (250 - 273.15)? = -23.15 C. Taking a step closer to your value:? 539 / 999 * 5 = 2702? or 270.2 K ?? 270.2 - 273.15 => -2.88 C
Then you could verify the output of the status message vs the telemetry data and see if it really is negative, or just rounding off poorly.
On Tuesday, June 29, 2021, 8:05:52 PM EDT, py5lf_ < py5lf@...> wrote:
<Snip> Robert LM335DZ encapsulated?to put outside ...
Em ter., 29 de jun. de 2021 ¨¤s 20:50, py5lf_ via <py5lf= [email protected]> escreveu: Robert This temperature comes from the LM335DZ put outside my shack , using a shielded cable . Also I have a Davis Vantage Vue connected to this TT4. But the main point is this ; TT4 doesn't?show a negative value on Celsius . After reaching zero , the value stays the same , while the temperature in Fahrenheit still works correctly. t^and T^ come from LM335.?
Em ter., 29 de jun. de 2021 ¨¤s 15:20, Rob Giuliano via <kb8rco= [email protected]> escreveu: Are you sending the temperature from a Davis Weather Station, the Temp sensor on the TT4, or a Temp sensor on a different TT4 analog input?? (assume not the last as it wouldn't be converted to degrees inside the TT4)
On Tuesday, June 29, 2021, 9:44:18 AM EDT, py5lf_ < py5lf@...> wrote:
Friends As you can see TT4 cant send temperatures below zero in Celsius; 2021-06-29 06:29:04 -03:?>APTT4,WIDE1-1,WIDE2-1,qAR,:WX?Davis,FTM100DR,5W,GP6,Ext.Temp.:0C,30F,DGP=OFF? 30F = -1C Any solution ? --
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-- Richard A. Painter, P.E. Retired
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Rich Painter