[time-nuts] Any experienced HP 2804A thermometer users outthere?
Didier
didier at cox.net
Sat Jan 24 21:24:09 UTC 2009
I have never used the 1-wire sensor, but I have actually used Thermochrons
recorders from Dallas Semi, I still have some in equipment, and I have one
in my car at the moment :-)
But there are cases where there are too big, or they are in a noisy
environment, and a thermistor is more flexible.
Another advantage of the thermistor is the low overhead to make a reading.
On most ucontrollers, the ADC runs under interrupts, so it does not take
much resources to make a reading. It's only if you want to convert the
reading in degrees that you have to run a linearization routine. For low
precision needs, I just use an 8 bit lookup table. That gives precision
better than a degree C around 25 C with very little CPU time. It's plenty
for things like thermal protection or temperature compensation.
The 18B20 is almost as small as a thermistor, but I do not have code for it.
Can't be too hard though.
Thanks for the pointer,
Didier
> -----Original Message-----
> From: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Poul-Henning Kamp
> Sent: Saturday, January 24, 2009 1:48 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Any experienced HP 2804A thermometer
> users outthere?
>
> In message <CD547DCFF6D34F198AF32525FEC677B6 at didierhp>,
> "Didier" writes:
>
> For permanent measurement points, I prefer the Dallas DS18B20
> 1-wire sensors, they interface to a single I/O pin on
> anything programmable and gives 1/160C resolution and +/-
> .50C precision.
>
> --
> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG | TCP/IP since RFC 956
> FreeBSD committer | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by
> incompetence.
>
>
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