Electronics > Metrology

LTZ1000 Supply

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--- Quote from: e61_phil on February 13, 2016, 07:34:26 pm ---
--- Quote from: quarks on February 13, 2016, 07:31:42 pm ---about the battery, I would probably try to use a power tool battery, because I have quite a few, so I can easily charge and change them very fast.

--- End quote ---

Nice idea :) and an internal power supply to keep all the things running during change?

--- End quote ---

exactly, the only problem I have not yet solved, is a mounting adapter for my Bosch accus..

For a reference that is supposed to run 168 h per week, fast heating is not that important. Anyway it does not make a big difference if initial heating is reduced from 5 minutes to maybe 2 minutes - thermal stabilization of the circuit needs longer anyway. For battery operation there should be enough isolation / cover directly at the LTZ1000 that you don't need that much power.

If a second oven is used, the power to the LTZ1000 would be rather close to minimum - so far that one might even consider to change the temperature regulation part to work better at low power (e.g. more gain or even a square root circuit). A lower voltage may actually be good to limit the maximum heater power in case of an upset to the control circuit - just in case.

Using battery packs from power tools might be handy because of the fast chargers, but usually these packs are relatively expensive. You may find a mounting adapter as a spare part: the one for the 14.4 or 18 V Li Packs from Bosch costs about 10 EUR. A broken old machine or charger would be an option too.

I think I will stay at the sealed-lead-acid battery. I can connect the reference to line voltage and forget about it for weeks or even month. And I never have to change the batterie for charging.

From my past test record, any voltage above 9V will do(<=15V). When supply vary from 8.9V to 12V, the output changes less than 0.5ppm.
This is for my LTZ1000 running at 45 deg C internally, and the room temperature of around 23 deg C.
To be on the safe side, >10.5V is suffice. Therefore, two 6V battery in series will do the job.
If you supply higher voltage at 18V, the opamp and the heater control transistor will generate more heat, and no good at all. One more thing, two batteries and three batteries last the same time.
Even you have a 7V to 10V resistive divider boost, you can still running the whole circuit on 12V as Fluke people do in their 732B.


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