wetbulb?
Posted: Fri 24 Jan 2014 1:23 am
Hi Steve,
What formula does cumulus use to do wetbulb?
Thank Beau
What formula does cumulus use to do wetbulb?
Thank Beau
Cumulus Support
Support forum for Cumulus weather station software
https://cumulus.hosiene.co.uk/
wetbulb?
Page 1 of 1
Re: wetbulb?
Posted: Fri 24 Jan 2014 1:35 am
Based on the one I gave here I think: https://cumulus.hosiene.co.uk/viewtopic.p ... lb&start=0
Re: wetbulb?
Posted: Fri 24 Jan 2014 8:09 am
I ended up using a direct formula that appears on the web in various places (e.g. here: http://www.aprweather.com/pages/calc.htm) which doesn't use an iterative approach (and is possibly hence slightly less accurate).
Re: wetbulb?
Posted: Sat 25 Jan 2014 12:19 am
ok I missed something
htp://99.108.42.167/weather/test3/wxwetbulb.php
htp://99.108.42.167/weather/test3/wxwetbulb.php
Code: Select all
use these numbers
$Tc = -2.0555555555556
$RH = 51
$P = 1012.7337934
i get 3.9960679808406
cumulus 24.5
Code: Select all
<?php
############################################################################
# A Project of TNET Services, Inc. and Saratoga-Weather.org (Canada/World-ML template set)
############################################################################
#
# Project: Sample Included Website Design
# Module: sample.php
# Purpose: Sample Page
# Authors: Kevin W. Reed <kreed@tnet.com>
# TNET Services, Inc.
#
# Copyright: (c) 1992-2007 Copyright TNET Services, Inc.
############################################################################
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
############################################################################
# This document uses Tab 4 Settings
############################################################################
require_once("Settings.php");
require_once("common.php");
############################################################################
$TITLE = langtransstr($SITE['organ']) . " - " .langtransstr('wetbulb test page');
$showGizmo = true; // set to false to exclude the gizmo
include("top.php");
############################################################################
?>
</head>
<body>
<?php
############################################################################
include("header.php");
############################################################################
include("menubar.php");
############################################################################
?>
<div id="main-copy">
<?php echo 'temperature: '.$WX['temp'];?><br />
<?php echo 'humidity: '.$WX['hum']; ?><br />
<?php echo '$baro: '.$WX['press']; ?>
<br />
<?php echo'wetbulb: '. $WX['wetbulb']; ?><br />
<?php
$Tc =($WX['temp']-32)/1.8;
$P = 33.8639 * $WX['press'];
$RH = $WX['hum'];
echo'$Tc = '. $Tc.'<br />';
echo'$RH = '. $RH.'<br />';
echo'$P = '. $P.'<br />';
echo'<br />';
//echo $tc;
$Tdc = (($Tc - (14.55 + 0.114 * $Tc) * (1 - (0.01 * $RH)) - ((2.5 + 0.007 * $Tc) *
(1 - (0.01 * $RH))) ^ 3 - (15.9 + 0.117 * $Tc) * (1 - (0.01 * $RH)) ^ 14));
$E = (6.11 * 10 ^ (7.5 * $Tdc / (237.7 + $Tdc)));
$WBc = (((0.00066 * $P) * $Tc) + ((4098 * $E) / (($Tdc + 237.7) ^ 2) * $Tdc)) / ((0.00066 * $P) + (4098 * $E) / (($Tdc + 237.7) ^ 2));
echo '<br />';
echo $WBc;
?>
</div><!-- end main-copy -->
<?php
############################################################################
include("footer.php");
############################################################################
# End of Page
############################################################################
?>
Re: wetbulb?
Posted: Sat 25 Jan 2014 2:10 am
Edit: code corrected - thanks to mark 
$Tc = -2.0555555555556
$RH = 51
$P = 1012.7337934
Tdc= -10.877659778338
E= 2.6691050528504
$WBC = -4.1844761761292 WBf = 24.5
You are NOT using php math !
2 ^ 3 is not php, pow(2, 3) is ..The figure now agrees (Deg F) with what you say Cumulus gives
You are still using Relative (sea level) instead of Absolute (station) pressure, although this will only make a (very) small difference.
$Tc = -2.0555555555556
$RH = 51
$P = 1012.7337934
Tdc= -10.877659778338
E= 2.6691050528504
$WBC = -4.1844761761292 WBf = 24.5
You are NOT using php math !
2 ^ 3 is not php, pow(2, 3) is ..
Code: Select all
$Tdc = (($Tc - (14.55 + 0.114 * $Tc) * (1 - (0.01 * $RH)) - pow((2.5 + 0.007 * $Tc) * (1 - (0.01 * $RH)) , 3) - (15.9 + 0.117 * $Tc) * pow(1 - (0.01 * $RH), 14)));
$E = (6.11 * pow(10 , (7.5 * $Tdc / (237.7 + $Tdc))));
$WBc = (((0.00066 * $P) * $Tc) + ((4098 * $E) / pow(($Tdc + 237.7) , 2) * $Tdc)) / ((0.00066 * $P) + (4098 * $E) / pow(($Tdc + 237.7) , 2));
You are still using Relative (sea level) instead of Absolute (station) pressure, although this will only make a (very) small difference.
Re: wetbulb?
Posted: Sat 25 Jan 2014 10:02 am
beteljuice, you still have a '^' lurking in the Tdc calculation
Re: wetbulb?
Posted: Sat 25 Jan 2014 11:03 am
Well spotted .. thank you Mark.
Post edited with new results and code correction.
Post edited with new results and code correction.
Re: wetbulb?
Posted: Sat 25 Jan 2014 2:40 pm
thank you beteljuice and Mark