Thys, can you tell me how do you scale the output signal of LM35 to obtain
full AD pic resolution and how do you convert for displaing celcius
degrees. AT 0C LM35 output is about 2.7315V and depends of biasing
current. At 100C will be about 3.73V For a 0..5V AD input, probably you
need a diferential amplifier or for a pic16F877 to set -ref at 2.73 and
+ref at 3.73 but in this case you will not have 10 bit AD resolution.
Is there any more simple method to do that without external amplifiers
and of course without any one wire or i2c temperature measurement devices.
Thank's very much,
Vasile=20


On Wed, 7 Feb 2001, Thys Van Tonder wrote:

> Hi there Peter
>=20
> The LM335 gives you 10mV/=B0K. So you better use shielded cable. I used t=
he
> LM35 with about 4m
> of cable and it worked fine for our application, a bit of switching noise
> from the motors we were probing. You can average out your reading in the
> software.
>=20
> Regards
> Thys
>=20
> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Peter May
> Sent: 07 February 2001 08:13
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [PIC]: LM335
> Importance: Low
>=20
>=20
> I gave up on the DS18S20's and went to a simple LM335. It says in the dat=
a
> sheet I can run a long cable to it and use it remotely. In the finished
> product it will be within a couple of inches of the PIC but for bench
> testing I want about 20 feet of cable. Would this introduce much noise in=
to
> the analogue input?
>=20
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>=20
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