I am going to try and create a better board for my 2DW23x - to get some long-term drift data - which at the moment is missing information.
In the meantime, I found a source for some minature peltier coolers. This would open the possiblity of replacing the heating loop used for thermal stabilisation with a Peltier cooler to do the same thing. The regulation temperature could be set to co-incide with expected room temperature - say 23C.
Advantages,
- less thermal stress on the 2DW23x when cycling between use and non-use. Reduced hysteresis issues. Also between the time that the part is manufactured and the time that it is deployed/used.
- It feels elegant to balance the heating effect from the 20-30mA zener current with a cooling loop. At the moment there needs to be enough headroom above the ordinary heated temperature for the temperature regulation loop to have room to work in various ambient settings.
- The poor power efficiency of Peltier devices is discouraging. But if we accept that the reference is already high-current then it seems less of an issue.
- lower thermal gradients over the device - because the regulation setpoint is closer to ambient temperature.
- More amenable to the carrier board solution - to keep the precision resistors at the same temperature as the 2DW23x. This is because of the lower second-order TCR affects of the Z201 around 25C .
Disadvantages,
- Is it just really over-complexifying the design, and assembly?
Some more details,
http://blog.julian1.io/2017/02/16/2dw232-circuit-7.html