Re: How to keep part at constant temperature


Mike Noone wrote:
John Larkin wrote:
If you feed back on each gyro's temp sensor, you can use a local
resistor to heat each gyro chip. The loop will probably be tricky to
stabilize. Use duty cycle modulation to drive the heaters to avoid e^2
nonlinearity problems. I like to glue a thin pcb to a big aluminum
plate, slap a Minco heater or a few power fets on the bottom and a
surface-mount thermistor on top, close that loop at 60C, and populate
the board with surface-mount parts. That rig has good loop dynamics.

I don't understand why I wouldn't be able to keep it fairly stable. I
mean - outside temperature should be relatively constant - so it should
be able to slowly ramp up the duty cycle to the heating resistors till
they get it hot enough. I've never made such a device so I'm speaking
entirely theoretically, though.

Yes, you can keep it stable, but the amount of energy wasted would be
significant. I built a insulated cube of 6 inches to keep the inside
temperature at 40C (15C above environment). My rough estimate is at
least 3 to 4W energy wasted. 60C is not a simple task.

Have you checked the power budget on this flight instrument?


You could also just measure the temperature and apply a fudge factor
to the output signal.

Yes, temperature compensation table would be much easier.


Except that according to the Analog data*** - if I'm reading it right
- some parts keep the same sensitivity when temperature changes. So I'd
have to calibrate it for each part - which would be difficult and
annoying.

But I don't think you can get anywhere near usable stability for your
application (the inertial navigation thing, right?) even if you do
temp regulate these parts. Probably not by 3-6 orders of magnitude.

Yup - same IMU project.

Thanks,

-Mike

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