For the final packaging/mounting of the sensor to the seismometer, I have thought of two options.
1. Attach circuit to a PCB board and place it inside the can, while leaving the AD590 open to the air inside the can.
- This makes sure that the sensor gets a direct measurement of the temperature of the air in the can, as it is exposed to the air.
- But, it takes a limited area of measurement, so it could be the case that the area we place it in happens to be a hot or cold pocket, and the measurement would be inaccurate.
- This can be solved by placing multiple copies of the circuit in various places of the can and averaging the values.
2. Attach the AD590 to a copper plate with thermal paste and put it into a pomona box.
- This solves the problem of having a limited sample area the first option had, as the copper plate should have a uniform temp distribution, thus we are sampling the temp of that whole area.
- Need to make sure that the response time to the temperature variations of copper is less than the frequency that we are measuring.
- This can be calculated using equations for heat transfer (listed below).
If anyone has input on which method is preferred or any additional options that we may have, I would appreciate it.
Heat transfer:
q = k A dT / s
- k = thermal conductivity
- A = area
- dT = temperature gradient
- s = thickness
For copper, k = 401 W/mK, x = 1.27 mm, A = 2.66x10^-3 m^2 (for the particular copper plate I measured), dT = 1K (assume). Thus the heat transfer will be 839 J/s.
I'm not completely sure what to do with this yet, but it could help us decide whether the copper plate option will be useful for us.
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