[time-nuts] Any experienced HP 2804A thermometer users out there?

Henk Termeer henk.termeer at gmail.com
Sat Jan 24 16:58:11 UTC 2009


Hello John,

I have been searching for pictures and found this
http://www.harlanlabs.com/2804a.jpg if you have a probe like this, no grease
will help you.
The quartz cristal is some where in the bulp on the end of the probe and is
not in direct contact, just like a cristal for a osicillator (because it has
to be able to move), so the thermal resistance between the bulp and the
cristal is high. If you make contact to a pc board, you will measure
something between the enviroment temperature and the board temperature, but
you will never know what you measure most.
This probe is excelent for calibration in liquits or gas but you have to
insert it at least 20 cm.

Best regards,

Henk

On Sat, Jan 24, 2009 at 5:39 PM, John Ackermann N8UR <jra at febo.com> wrote:

> The best I can get. This is time-nuts, after all.  :-)
>
> I'm certainly not looking for the full millidegree accuracy of the
> thermometer, but have always been curious about heat transfer issues
> with thermometer probes and wondered if there were any tricks apart from
> laying the end of the probe horizontally on the board (maybe with the
> help of some thermal grease, as Brooke suggested).  The challenge is the
> relatively small contact area between the circular probe and the flat
> board, and the corresponding fact that the majority of the probe's
> surface area is in contact with the ambient air rather than the surface
> of interest.
>
> John
> ----
>
> Mike Feher said the following on 01/24/2009 11:15 AM:
> > What type of accuracy are you looking for John?
> >
> >
> >
> > Mike B. Feher, N4FS
> > 89 Arnold Blvd.
> > Howell, NJ, 07731
> > 732-886-5960
> >
> >
> > -----Original Message-----
> > From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> > Behalf Of John Ackermann N8UR
> > Sent: Saturday, January 24, 2009 10:42 AM
> > To: Discussion of precise time and frequency measurement
> > Subject: [time-nuts] Any experienced HP 2804A thermometer users out
> there?
> >
> > The temperature probes for the 2804A quartz thermometer seem primarily
> > intended for liquid immersion.  I'm looking for practical tips on how to
> > couple the probe to a solid surface (e.g., a PC board) for accurate
> > temperature measurements of the surface.
> >
> > Anyone know the best way to do this?
> >
> > Thanks,
> >
> > John
> >
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