No subject

Normal ground drop due to heater current is around 0.5mV max at room
temperature.
This corresponds to about a frequency off set of 1.5 -4.5 E-11 depending
on the model.
Since the heater current could be 5x this at low temperatures the
corresponding frequency offset will be around
7.5- 22.5E-11 depending on model (neglecting the decrease in the wiring
resistance as the temperature drops).

Since the temperature drift is 1-2E-9 the effect of the varying ground
voltage drop is 5 -10 x smaller, it doesn't really matter whether the
EFC pin is grounded or not during temperature testing.

Bruce