Has anyone had significant success with the "Adjusting Temperature Coefficient in Unstabilized Applications" typical application circuit on the LTZ1000 datasheet? The one where you cycle the heater on and off at one minute intervals while tweaking the bias current for minimum TC.
I was wondering how low a TC it is possible to achieve using this method. Given that the datasheet specifically states that drift increases with high temperature, then for an ultimate goal of minimum long term drift, I'm wondering if this first order temperature compensation, maybe coupled with a thermometer (standard cell style of working) and/or basic external oven is a viable option. Minimizing Kovar lead thermocouple issues too.
As I say, sorry if this has already been covered.
Hello,
no problem, I think nobody ever has given a final conclusion about that feature.
And I think, I have read every entry here!
First of all, you are mixing T.C. and long term drift.
Both characteristics have nothing in common, and must be discussed separately.
Long term drift is determined by the oven temperature, the lower, the better.
45°C gives about -1ppm/year.
High quality external resistors (5 EA) add about +/- 0.3ppm/year or less, as their impact on all drifts is attenuated by factors of 1/100.. 1/1000.
The T.C. for a stabilized solution (using the internal oven) is determined only by the external resistors ( to first order), and therefore being < 0.1ppm/°C in most cases (using < 3ppm/°C resistors)
The reference element itself has a T.C. (un-stabilized, no oven) of about 50ppm/°C.
Only if you do NOT use the oven, a trimming of this characteristics is needed /makes sense.
In the stabilized case, the oven regulation is so good, that it reduces these 50ppm/°C to unmeasurable values, i.e. being much lower than the impact of the external resistors.
This fact and the probable complication of the trimming resistor might explain, why nobody has put much effort in this feature.
Frank