Warm-up Time for 3 Phase Power Analyzers

Hi,
I am trying to understand the technical specifications of three phase power analyzers and I see a "warm-up time" mentioned for a couple of
products.
For example:
Amplitude accuracy     0.05% rdg. 0.01% f.s. (DC, or 45 to 66Hz, after 10 minutes of warm-up time) Phase accuracy     0.2 (45 to 66 Hz, after 10 minutes of warm-up time)
(See: http://www.hioki.com/product/3390/index.html bottom of the page)
I see some other brands that require upto 30 minutes of warm-up time.
I would like to know why this warm-up time is required and possible solutions to the problem.
Thank you for your time.
Thanks, Anand
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Anand P. Paralkar wrote:

If it is a precision device, which most likely it is, it's very common to have warm up times. The device was calibrated at a fix temperature and thus can effect precise readings. For rough or average readings, you can get away with out waiting for it.. But expect the reading to be a little different, if only by a very small fraction after the unit has warmed up.
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What he said.
We had some precision equip. years ago that had a crystal oven in it to keep the crystal oscillator running at an exact freq. It took a few minutes to insure the crystal was warm enough.
If it is a precision device, which most likely it is, it's very common to have warm up times. The device was calibrated at a fix temperature and thus can effect precise readings. For rough or average readings, you can get away with out waiting for it.. But expect the reading to be a little different, if only by a very small fraction after the unit has warmed up.
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What he said.
We had some precision equip. years ago that had a crystal oven in it to keep the crystal oscillator running at an exact freq. It took a few minutes to insure the crystal was warm enough.
If it is a precision device, which most likely it is, it's very common to have warm up times. The device was calibrated at a fix temperature and thus can effect precise readings. For rough or average readings, you can get away with out waiting for it.. But expect the reading to be a little different, if only by a very small fraction after the unit has warmed up.
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What he said.
We had some precision equip. years ago that had a crystal oven in it to keep the crystal oscillator running at an exact freq. It took a few minutes to insure the crystal was warm enough.
If it is a precision device, which most likely it is, it's very common to have warm up times. The device was calibrated at a fix temperature and thus can effect precise readings. For rough or average readings, you can get away with out waiting for it.. But expect the reading to be a little different, if only by a very small fraction after the unit has warmed up.
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On 11/28/2010 08:14 AM, Anand P. Paralkar wrote:

As has been mentioned, this is pretty common. When you get to this sort of precision you have to pay close attention to the temperature of the various bits of the circuit. Even if you get that part solved, right after system turn-on the temperature differences between the various bits of the circuit won't be the same as when it has sat and stabilized for a while -- hence the need for warm up.
I can think of four ways to solve this problem, all requiring at least some time and trouble:
1: Keep the thing turned on. Then it'll always be warm, and you'll be operating it within it's ratings.
2: Calibrate the thing right after turn on, and only use it as part of a cycle where it sits still for a good long time, then gets turned on and a measurement taken, then it gets turned off.
3: Build a unit that is proof against these effects. It won't be easy, I'm sure I couldn't even guess what all the effects are that you'd have to address (although keeping hot parts remote from measurement heads, and building the measurement heads so that all their parts are very tightly thermally coupled are the first two things I'd do). Expect to expend man-years -- possible man-decades -- of engineering work on this, unless you're _really_ _really_ smart.
4: See if the manufacturer will sign up to some relaxed specifications during warm up, and if those are good enough for you then use the system any old time.
--

Tim Wescott
Wescott Design Services
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Tim Wescott wrote:

[snip]
5. Expect trouble from the electronics tech union if warm-up times are reduced as this will cut into those extra coffee breaks. ;-)
--
Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
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Paul Hovnanian P.E. wrote:

And steer clear of the unicorns and flying pigs.
They can be brutal. :)
--Winston
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