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fix: dewpoint was missing

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git-svn-id: https://svn.fhem.de/fhem/trunk@879 2b470e98-0d58-463d-a4d8-8e2adae1ed80
This commit is contained in:
wherzig 2011-03-27 14:33:20 +00:00
parent a5c65608f9
commit 02f1aa43ba
1 changed files with 28 additions and 0 deletions
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28
fhem/FHEM/70_USBWX.pm
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@ -371,6 +371,34 @@ Log 4, "USBWX SimpleWrite $msg";
select(undef, undef, undef, 0.001);
}
# -----------------------------
# Dewpoint calculation.
# see http://www.faqs.org/faqs/meteorology/temp-dewpoint/ "5. EXAMPLE"
sub
dewpoint($$)
{
my ($temperature, $humidity) = @_;
my $dp;
my $A = 17.2694;
my $B = ($temperature > 0) ? 237.3 : 265.5;
my $es = 610.78 * exp( $A * $temperature / ($temperature + $B) );
my $e = $humidity/ 100 * $es;
if ($e == 0) {
Log 1, "Error: dewpoint() e==0: temp=$temperature, hum=$humidity";
return 0;
}
my $e1 = $e / 610.78;
my $f = log( $e1 ) / $A;
my $f1 = 1 - $f;
if ($f1 == 0) {
Log 1, "Error: dewpoint() (1-f)==0: temp=$temperature, hum=$humidity";
return 0;
}
$dp = $B * $f / $f1 ;
return($dp);
}
#####################################
sub