[time-nuts] Temperature sensors and bridge amps

[Bill Hawkins]

Rick,

Is the double integrator actually a cascade of two controllers,
where the primary controls the crystal temperature and its
output sets the setpoint for a heater temperature controller?

That's how industrial control handles the lag between a 5000
gallon reactor and its steam-heated jacket. There's a sensor and
primary PID for the reactor contents (stirred) and a sensor and
PID for the jacket temperature.

When I said "ambient" I was thinking of the range that a military
receiver like the R-390 was designed for.

Seems to me that if the only disturbance to the crystal temperature
is the ambient temperature, then you can lag ambient with enough
insulation so that the internal controller can be slow enough to
have adequate gain.

There are disturbances within the internal loop that would have
to be dealt with, such as the heater supply voltage and the offset
voltage of the first error amplifier.

We are going for stability, not accuracy, right?

Bill Hawkins

P.S. Really good story to wind up the "loosing things" thread.
 

-----Original Message-----
From: Richard Karlquist
Sent: Saturday, November 13, 2010 3:24 PM

 Yes, E1938A.  I was operating on limited sleep when I posted that.

 Rick

 On Sat 13/11/10 8:35 AM , Magnus Danielson  wrote:

 On 11/13/2010 04:48 PM, Richard Karlquist wrote:
 > The HP E9183A achieved 1 millidegree over -55 to +85C
 > in a single oven. The time lag was dealt with by adding
 > a double integrator to PID.

 I'd assume you would intend to write HP E1938A, right?

 Cheers,
 Magnus

 > Rick Karlquist N6RK
 >
 > On Fri 12/11/10 8:26 AM , "Bill Hawkins" wrote:
 >
 > in the heater control loop. Of course, you can't get to a
 > millidegree from ambient with just one oven. And you can't
 > eliminate time lags if you have any thermal mass.
 >