Electronics > Metrology

Lowest drift, lowest noise voltage reference (ADR1000AHZ)

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iMo:
You would need 11.8V on the internal 240ohm heater to get 580mW, that is aprox 150C on chip provided the case is 216C/W thermal resistance and ambient is 25C.
PS: the internal heater resistance is specified around 240ohm at 1mA heater current in the DS. It could be pretty different at 49mA (and such high temp), however..

manganin:

Years ago I built an aging rig for the AD587 references. The total power comsumption of 100 chips was so high, that no separate heater was needed. The temperature control loop simply adjusted the supply voltage.

Thanks to the distributed heat source, the temperature gradients were minimal. So I could trust that all the chips got the same treatment.

Smaller number of chips (less power dissipated) requires of course better insulation to get the same temperature.

Andreas:
Hello,

update on ageing drift of my ADR1000A#01 + #02 now at 5 kHrs
see also:
https://www.eevblog.com/forum/metrology/lowest-drift-lowest-noise-voltage-reference/msg4397278/#msg4397278

the 6.6V zener outputs still drift -0.3 ppm/khr while the 10V output is better (the voltage divider drifts the other direction most probably due to still high humidity).
The Jump on ADR#02 on day 180 by +0.7ppm was created by a flat battery for ~3 days (I had forgotten to attach the charger).
At the same time I had also a Jump of 0.4 ppm on the LTZ9 sanity check so not all of the 0.7 ppm are true.
But afterwards I have still a permanent hysteresis of ~0.4 ppm due to the power off phase.

So regarding hysteresis this observation confirms the measurements of Dr. Frank.
https://www.eevblog.com/forum/metrology/lowest-drift-lowest-noise-voltage-reference/msg4398226/#msg4398226

with best regards

Andreas

branadic:
I guess we can call it "All Drift Reference 1000"  :-DD
My experiment is still running too, but it is not yet conclusive. At some point (after around 6000 - 7000 h) the drift changed sign and is now drifting upwards instead of downwards.

-branadic-

branadic:
Let me share an update of my measurement results (10V output, so we don't look at the raw zener voltage).
Any shift of the signals can be explained by either turning on/off instruments, removing equipment from the setup, changing batteries and the like, so what really counts is the overall behavior of the references, not the details.
What can be observed is a downward drift first, a change in sign second, followed by a steady state at the moment, while we have to be patient how that evolves next.

My current suggestion for a future experiment is to have three ADR references running at different oven temperatures:

1. running ADR oven at its zero t.c. temperature (~50 °C, that is a resistor ratio of about 11.5:1 for the datasheet circuit or about 0.52 V for the circuit using the temperature sensing transistor as a diode)
2. running ADR at 75 °C oven temperature (that is a resistor ratio of about 13:1 for the datasheet circuit or about 0.465 V for the circuit using the temperature sensing transistor as a diode)
3. running ADR at 100 °C oven temperature (that is a resistor ratio of about 14.6:1 for the datasheet circuit or about 0.41 V for the circuit using the temperature sensing transistor as a diode)

The comparison of the drift between these three references should indicate what time it takes for the references to stabilize at which temperature, though it's not an abolute measure. Once stabilized the oven of the latter two references can be set to the zero t.c. temperature of their zener. For this experiment I would use the raw zener voltage buffered and preferable nanovoltmeters to measure the differences.

-branadic-

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