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<DIV><FONT face=Arial size=2>We used to use an Analog Devices current source
temperature sensor. They sold in a wide range of accuracies, from IIRC
+/- 5 degrees to +/- 0.1 degrees. I forget the exact numbers but the
accurate ones were like 100 times more expensive than the cheaper ones. Then, to
get the accuracy you had to use high precision parts in the entire analog
circuit. For example if you had an 8 bit A/D and were measuring an indoor
temperature range of 50 degrees (total range of 50-100 degrees) a single
bit error would throw you off 2 tenths of a degree, so we had to use a 10 bit
A/D. And to eliminate the need to calibrate we needed to eliminate slop caused
by resistors so we had to buy 1% precision instead of the 5-10% popcorn parts.
So the end product ended up costing something like 300% more. Our system was
already at the high end of the price curve so it was deemed
impractical.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>The $20 Radio Shack thermometer you mention
has an advantage over any field wired sensor. The length of the wire is
known and it can be calibrated in a factory. The use of any of the cheap voltage
style sensors can be made accurate if the total system, including wire length,
is known. In a custom home the wire length cannot be known. Longer wires cause
more voltage drop which can greatly affect accuracy. In this type of system a
different type of sensor has advantages, like a current source (current varies
with temperature) or frequency (frequency varies with temperature). Those types
of sensors are more expensive but relatively immune to different lengths of wire
used to hook them up.</FONT></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=looney2ns@sigecom.net href="mailto:looney2ns@sigecom.net">Brad</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=kwschumm@qsolv.com
href="mailto:kwschumm@qsolv.com">'Ken Schumm'</A> ; <A
title=hai-users@tssi.com
href="mailto:hai-users@tssi.com">hai-users@tssi.com</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, January 13, 2006 1:58
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> RE: [Hai-users] Temp sensors
accuracy again.</DIV>
<DIV><BR></DIV>
<DIV class=Section1>
<P class=MsoNormal><FONT face="Times New Roman" color=black size=3><SPAN
style="FONT-SIZE: 12pt; COLOR: black">Ken, not sure what you mean by expensive
parts, but I sure don’t consider what the temp/humid sensor HAI sells as
cheap.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" color=black size=3><SPAN
style="FONT-SIZE: 12pt; COLOR: black">It’s sad, when Radio Shack can sell $20
temp/humid displays that all hit the correct temps and humid % almost dead
on.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" color=black size=3><SPAN
style="FONT-SIZE: 12pt; COLOR: black"><o:p> </o:p></SPAN></FONT></P>
<DIV>
<DIV class=MsoNormal style="MARGIN: 0in 0in 0pt; TEXT-ALIGN: center"
align=center><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt">
<HR tabIndex=-1 align=center width="100%" SIZE=3>
</SPAN></FONT></DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><B><FONT face=Tahoma
size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">From:</SPAN></FONT></B><FONT
face=Tahoma size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma"> <A
href="mailto:hai-users-bounces@tssi.com">hai-users-bounces@tssi.com</A>
[mailto:hai-users-bounces@tssi.com] <B><SPAN style="FONT-WEIGHT: bold">On
Behalf Of </SPAN></B>Ken Schumm<BR><B><SPAN
style="FONT-WEIGHT: bold">Sent:</SPAN></B> Friday, January 13, 2006 2:24
PM<BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B> <A
href="mailto:hai-users@tssi.com">hai-users@tssi.com</A><BR><B><SPAN
style="FONT-WEIGHT: bold">Subject:</SPAN></B> Re: [Hai-users] Temp sensors
accuracy again.</SPAN></FONT><o:p></o:p></P></DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P>
<DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Comic Sans MS"
size=3><SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 'Comic Sans MS'">I used to
work for a company that manufactured a proprietary commercial building
control system. We tried for years to come up with an inexpensive
and reliable way to accurately measure temperature to +/- 0.1 degree that
didn't require field calibration. The only way we found to solve that
problem was to use expensive components (sensors, precision resistors, etc)
that significantly raised the price of the systems. Marketing balked at
the price and it never did happen.</SPAN></FONT><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman"
size=3><SPAN style="FONT-SIZE: 12pt"> <o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Comic Sans MS"
size=3><SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 'Comic Sans MS'">Not a
solution to your problem but if HAI can't solve the problem maybe they need to
come up with an easy and supported way to field calibrate the
parts.</SPAN></FONT><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman"
size=3><SPAN style="FONT-SIZE: 12pt"> <o:p></o:p></SPAN></FONT></P></DIV>
<BLOCKQUOTE
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<DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">----- Original Message -----
<o:p></o:p></SPAN></FONT></P></DIV>
<DIV style="font-color: black">
<P class=MsoNormal style="BACKGROUND: #e4e4e4; MARGIN: 0in 0in 0pt"><B><FONT
face=Arial size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Arial">From:</SPAN></FONT></B><FONT
face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"> <A
title=looney2ns@sigecom.net href="mailto:looney2ns@sigecom.net">Brad</A>
<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><B><FONT face=Arial
size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Arial">To:</SPAN></FONT></B><FONT
face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"> <A
title=hai-users@tssi.com
href="mailto:hai-users@tssi.com">hai-users@tssi.com</A>
<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><B><FONT face=Arial
size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Arial">Sent:</SPAN></FONT></B><FONT
face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"> Friday,
January 13, 2006 10:19 AM<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><B><FONT face=Arial
size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Arial">Subject:</SPAN></FONT></B><FONT
face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">
[Hai-users] Temp sensors accuracy again.<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman"
size=3><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P></DIV>
<P><FONT face="Comic Sans MS" color=black size=3><SPAN
style="FONT-SIZE: 12pt; COLOR: black; FONT-FAMILY: 'Comic Sans MS'"> Just
installed 3 HAI temp/humidity sensors. Also installed 3 HAI OmniStats with
remote temp sensors. The Thermostat remote sensors and the Temp/Humidity
sensors are mounted on inside walls within 6 inches of each other, each set
in a different room. Temp/Humidity sensors show temps being 3-5 degrees
higher than the thermostats show.<o:p></o:p></SPAN></FONT></P>
<P><FONT face="Comic Sans MS" color=black size=3><SPAN
style="FONT-SIZE: 12pt; COLOR: black; FONT-FAMILY: 'Comic Sans MS'">Apparently
HAI STILL has not resolved the issue of the Temp/Humid sensor’s being
inaccurate.<o:p></o:p></SPAN></FONT></P>
<P><FONT face="Comic Sans MS" color=black size=3><SPAN
style="FONT-SIZE: 12pt; COLOR: black; FONT-FAMILY: 'Comic Sans MS'">The
Humidity is reading low on them as well. Very
frustrating.<o:p></o:p></SPAN></FONT></P>
<P><FONT face="Comic Sans MS" color=black size=3><SPAN
style="FONT-SIZE: 12pt; COLOR: black; FONT-FAMILY: 'Comic Sans MS'">Anyone
else seeing this?<o:p></o:p></SPAN></FONT></P>
<DIV class=MsoNormal style="MARGIN: 0in 0in 0pt; TEXT-ALIGN: center"
align=center><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt">
<HR align=center width="100%" SIZE=3>
</SPAN></FONT></DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman"
size=3><SPAN
style="FONT-SIZE: 12pt">_______________________________________________<BR>HAI-users
mailing
list<BR>HAI-users@tssi.com<BR>http://romaine.tssi.com/mailman/listinfo/hai-users<o:p></o:p></SPAN></FONT></P></BLOCKQUOTE></DIV></BLOCKQUOTE></BODY></HTML>