[aprssig] FindU Telemetry page - Help needed
Steve Dimse steve at dimse.comFri Oct 10 20:02:25 UTC 2008
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Let me guess, you learned using the new math... if it doesn't involve apples or trains heading in opposite directions, you are lost ;-) First, this is also a linear system, which means that the a is zero. For a given change in the telemetered value, the measured parameter changed the same amount, whether the parameter change is from 99 to 100 or 1 to 2. Given it is linear, the formula is bx + c You are right, the problem is easier without converting to F, so let's do it in C first. The way you wrote it is (with an extra set of parens added for clarity) ((tele + 4.7) * 1.9608 ) - 273.15 it is just algebra to put this in the form bx + c distribute the multiplication ((tele x 1.9608) + (4.7 * 1.9608 )) - 273.15 4.7 * 1.9608 is 9.215, add this to the other constant -273.15 that makes the centigrade formula 1.9608 x + (-263.9) b = 1.9608 c = -263.9 solving for x = 148 gives 26.3 degrees C, a reasonable room temp so you want F? F = (C * (9/5) ) + 32 We know C is 1.9608x - 263.9 and 9/5 is 1.8 F = ((1.9608x - 263.9) * 1.8) + 32 Just like above, you distribute the 1.8, and add the two constants to get the b and c. This is left as an exercise for the reader. ;-) Steve K4HG On Oct 10, 2008, at 3:25 PM, Mark Cheavens wrote: > I am trying to work with the telemetry page on FindU. I have a > telemetry value that requires the attached math to make it display > the way I want. I haven't figured out how to make the math work to > get it to display correctly. Any help would be appreciated. > > Sample URL: > http://www1.findu.com/cgi-bin/tele1.cgi?call=PURG&last=96¶m=1&b=1.0&label=Purg_Repeater_Cabinet_Temp&units=Temperature&autorange=1 > > I am reading telemetry parameter 1. > > I need to take the value (Currently sitting on my bench in an air > conditioned room!) with a value of 148 > > I would LIKE to have the value in Degrees F (I know that C would be > easier)..... > > So here is the formula: > > ((Telemetry + Correction Factor) X 1.9608 Sensor Multiplier - 273.15) > * 5 / 9 - 32 = F > > For this install the correction factor is 4.7. > 1.9608 is the sensor multiplier (Constant) > The rest if just the basic math... > > OR ((148-4.7)*1.9608-273.15)*9/5+32=TempF > > I don't understand how the a= b= and c= can get me there! > http://www.findu.com/cgi.html#tele1 > > Any help would be appreciated! > > (I have figured out the easy linear ones in the past - Like this same > one for voltage - > http://www1.findu.com/cgi-bin/tele1.cgi?call=PURG&last=96¶m=2&b=.072254&label=Purg_Batt_Voltage&units=volts&autorange=1 > > (FYI - This is the output of an OpenTracker+ being used in an outdoor > solar only radio site (Emergency Clinic) to record interior > temperature for the batteries and battery voltage. - I do have it on > the status line, but I don't like the resolution, and would like to > plot it like I have done for the voltage) http://map.findu.com/purg > > > Mark > KC5EVE > > > > _______________________________________________ > aprssig mailing list > aprssig at lists.tapr.org > https://lists.tapr.org/cgi-bin/mailman/listinfo/aprssig >
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