Temp sensor for ID-1390 what is it?

[Clark, John]

Gerry, I use the LM135, LM334. It is a constant current device that has
a linear temperature error.  Makes a good sensor at the end of a long
wire run.

73
John Clark
N0URE


-----Original Message-----
From: wa1vwl [mailto:wa1vwl at grolen.com]
Sent: Tuesday, September 14, 1999 5:00 PM
To: HEATH at LISTSERV.TEMPE.GOV
Subject: Re: Temp sensor for ID-1390 what is it?


to my knowledge, there's no such thing as a linear temperature diode.
There is no such thing as a linear temperature element period.
Resistance Temperature Detectors (RTD) come pretty close but no cigar.
Don't even mention thermocouples. I hate working with them = low signal
output versus temperature change which means they need a lot of signal
conditioning. Thermistors are the least linear of all. Of course, they
all have their place in temperature measurement and control. The RTD's
in precision temperature measurement, thermocouples in harsh
environmental conditions, and thermistors in temperature control. Before
I get off my soap box, let me say that temperature linearization is done
in either the sensor interface circuit or in the signal conditioner
(read microprocessor) section of temperature readouts. I don't know
about the Heathkit units. I'm speaking based on my experience in the
field.

73/Gerry/W1ID

Tim C wrote:
>
> Mark and all,
> You are correct, the manual says nothing about what the potted diodes are!
> I had the exact same question today! So this morning I tried 2 switching
> diodes (1N914/1N4148) that seemed to work.  I have not determined if they
> are more linear than the original but all this will give you a starting
> point. Anyone know what diodes are specifically designed to offer a linear
> temp resistance?
> Tim
> W1TCC
> Cambridge MA
>
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