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

[Didier]

John,

The HP 3456A bench DMM can directly convert the reading from a specific 5k
thermistor (HP 0837-1064) into degree C or F with significant resolution.

I have not found the specification of the HP 0837-1064, but I have verified
that around 25 degrees, using two 10k thermistors of the type I use in my
projects (Murata NTSD1XH103FPB30, available from Digikey) in parallel gave
really well matching results. Of course, away from 25 degrees, precision is
not so good, even though repeatability and resolution are good, so it may be
useful to make comparison or stability measurements.

Using the NTSD1XH103FPB30 with a 12 bit ADC and a precision 10k resistor as
the other end of the bridge gives you repeatable performance to 0.1 degree C
(resolution around 25 C is 0.023 C) against a Fluke lab thermometer.

I have not tried with a 5k nominal thermistor in the same series.

The NTSD1XH103FPB30 thermistor is fairly small, but for best results, you
want to use very small wires, at least for a short distance from the
thermistor to reduce heat transfer through the wires.

To make a general purpose sensor with the thermistor, I glue it inside the
hollow part of a copper solder lug, and simply screw (or glue) the lug to
the object to be measured.

Didier KO4BB

> -----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 11:10 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Any experienced HP 2804A thermometer 
> users outthere?
> 
> David Forbes said the following on 01/24/2009 11:43 AM:
> 
> > What aspect of your measurement requires which amazing 
> property of the 
> > HP temp probe?
> > 
> > As others have said, matching the sensor to the thing to be 
> measured 
> > is of prime importance. Therefore, using the HP crystal 
> probe on a PC 
> > board is not an optimal solution.
> > 
> > I had to do PC board temperature monitoring a few years 
> ago, and found 
> > that I could get very good resolution with the Minco RTD 
> sensors that 
> > come attached to a small piece of Kapton tape.
> > 
> > http://www.minco.com/products/sensors.aspx?id=37
> 
> Dave, thanks for the pointer.  That looks like it might be a 
> good solution.
> 
> I don't *need* the HP probe accuracy, but being a time-nut 
> was curious to see how it might be used since I have one 
> available (and having the GPIB interface with no 
> voltage-to-temperature conversion required is also 
> convenient). But something tiny that tapes onto the board is 
> probably a much better solution in the real world.
> 
> Thanks,
> 
> John
> 
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