--------
In message <3897c09a-d76c-474c-8907-9ea25f8c3...@n1k.org>, Bob kb8tq writes:
>The “limited range” part of it is why the op-amp makes so much
>sense. If the ADC can “see” +/-10C that’s way more than will ever be useful.
Most uC's have a pile of mux'ed ADC inputs, so do all of the above:
AI0 = Full range
AI1 = +/- 10C
AI2 = +/- 2C
A big upside to this is that you will not need to invent heuristics
for clamped inputs in your PI(D) controller, something which is a bit
harder than most people realize.
Assuming a 10-bit ADC, the code will look something like this:
double
get_temp(void)
{
T = read_AI2();
if (T > 50 && T < 975) {
T += T2_offset;
T *= T2_scale;
return (T);
}
T = read_AI1();
if (T > 50 && T < 975) {
T += T1_offset;
T *= T1_scale;
return (T);
}
T = read_AI0();
if (T > 50 && T < 975) {
T += T0_offset;
T *= T0_scale;
return (T);
}
abort("You have problems...");
}
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
p...@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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