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Humidex question

Discussion and questions about Cumulus weather station software version 1. This section is the main place to get help with Cumulus 1 software developed by Steve Loft that ceased development in November 2014.
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fractonimbus
Posts: 159
Joined: Thu 03 Feb 2011 1:15 am
Weather Station: WH1091
Operating System: Windows 7 on a Dell Vostro
Location: Canberra

Humidex question

Post by fractonimbus »

One of the realtime.txt values is "Humidex". Is this what is also plotted in the standard C 1.9.1 web page as "Apparent Temperature"?

fracto
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nking
Posts: 813
Joined: Thu 17 Dec 2009 2:03 pm
Weather Station: W-8681
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Re: Humidex question

Post by nking »

No they are not the same, take a look at FAQ's.
fractonimbus
Posts: 159
Joined: Thu 03 Feb 2011 1:15 am
Weather Station: WH1091
Operating System: Windows 7 on a Dell Vostro
Location: Canberra

Re: Humidex question

Post by fractonimbus »

Yes, thanks, I found an earlier post on the subject, https://cumulus.hosiene.co.uk/viewtopic.php?f=14&t=3482

I've just coded the apparent temperature for PHP, which as a single equation is as follows:

$apptemp = round(($temp + 0.33*($hum/100)*6.105*exp(17.27*$temp/(237.7+$temp))- 0.70*$wspeed - 4.00),1);

I always use brackets (...) around anything where I don't trust the order of compuation (or don't know the language).
The round(x,1) command trims it back to one decimal place.

Here, $apptemp is the apparent temperature variable, $temp is the (dry bulb) temperature, $hum is the relative humidity, and $wspeed is the average windspeed. Seems to work OK.

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