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Keithley 2100,2000, etc or Chinese bench multimeters?

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Caliaxy:

--- Quote from: 2N3055 on October 28, 2024, 05:30:32 pm ---
--- Quote from: Caliaxy on October 28, 2024, 05:03:28 pm ---
--- Quote from: 2N3055 on October 27, 2024, 02:40:20 pm ---
--- Quote from: coromonadalix on October 27, 2024, 10:32:14 am ---
i'm waiting for a Siglent sdm3065   well see  .... but the reference voltage used is no par with the oldies with lm399 or the ltz1000 (3458a)


--- End quote ---

Rigol DM3068 and Siglent SDM 3065 also use LM399...

--- End quote ---

But not aged, allegedly (at least not in Siglent SDM3065), which makes them prone to drift in time, requiring more frequent re-calibrations.

--- End quote ---

What do you mean "more frequent" calibrations?

--- End quote ---

As needed to keep it on par with the ones with aged references (if precision matters that much).


--- Quote from: 2N3055 on October 28, 2024, 05:30:32 pm ---If reference is aged all you get is less drift on first calibration after a year.
After DMM is a year or two old, they all drift the same from that point on.
Aging is only accelerating initial drift, it does not make device better long term.

If you are aging and sorting you can pick best ones and then it would make the slight difference.
Which is not what happens for entry level 6.5 digit instrument even on big brands. For KS 3458 they will do it. For 34461 not really. Only some pre-aging.
Maybe KS 34465 has aged and selected LM399 because it claims better specs than 34460/61.

--- End quote ---
Yes, the drift slows down with time, until a point when it's not relevant anymore. SDM3065X only provides data for the first year (on par with 34461, indeed). Looking at the KS datasheets (for 34461 and 34465), the drift slows down a bit in the second year (by 25%). DMM6550 is more impressive, in two years drifts as much as the others in one. But they are all very small numbers.

2N3055:

--- Quote from: nctnico on October 28, 2024, 05:55:03 pm ---
--- Quote from: Caliaxy on October 28, 2024, 05:03:28 pm ---
--- Quote from: 2N3055 on October 27, 2024, 02:40:20 pm ---
--- Quote from: coromonadalix on October 27, 2024, 10:32:14 am ---
i'm waiting for a Siglent sdm3065   well see  .... but the reference voltage used is no par with the oldies with lm399 or the ltz1000 (3458a)


--- End quote ---

Rigol DM3068 and Siglent SDM 3065 also use LM399...

--- End quote ---

But not aged, allegedly (at least not in Siglent SDM3065), which makes them prone to drift in time, requiring more frequent re-calibrations.

--- End quote ---
Tony Albus shows that in a review of a GW Instek GDM-9061.

Around 16:00 he compares the GDM-9061 against the Siglent SDM3065 and the Siglent does seem to drift a bit.

--- End quote ---

I don't think what he shows is relevant in any way.

He stacked 10 instruments , including SDM3065, so close that air passages are blocked and instruments are heating each other in addition to not having any airflow. GDM-9061 is on desk with normal air flow.
So any "drifting" relative between these two instruments is irrelevant as a data point.

And you know that...

nctnico:

--- Quote from: Caliaxy on October 28, 2024, 06:44:20 pm ---
--- Quote from: 2N3055 on October 28, 2024, 05:30:32 pm ---
--- Quote from: Caliaxy on October 28, 2024, 05:03:28 pm ---
--- Quote from: 2N3055 on October 27, 2024, 02:40:20 pm ---
--- Quote from: coromonadalix on October 27, 2024, 10:32:14 am ---
i'm waiting for a Siglent sdm3065   well see  .... but the reference voltage used is no par with the oldies with lm399 or the ltz1000 (3458a)


--- End quote ---

Rigol DM3068 and Siglent SDM 3065 also use LM399...

--- End quote ---

But not aged, allegedly (at least not in Siglent SDM3065), which makes them prone to drift in time, requiring more frequent re-calibrations.

--- End quote ---

What do you mean "more frequent" calibrations?

--- End quote ---
As needed to keep it on par with the ones with aged references (if precision matters that much).

--- End quote ---
I don't think that will work. For as long as the drift hasn't made the readings go out of specification, there is no reason to adjust. A reference just needs to age to get rid of the initial drift.

2N3055:

--- Quote from: Caliaxy on October 28, 2024, 06:44:20 pm ---
Yes, the drift slows down with time, until a point when it's not relevant anymore. SDM3065X only provides data for the first year (on par with 34461, indeed). Looking at the KS datasheets (for 34461 and 34465), the drift slows down a bit in the second year (by 25%). DMM6550 is more impressive, in two years drifts as much as the others in one. But they are all very small numbers.

--- End quote ---

I am afraid you misunderstood what some of these specifications mean in datasheets.
1 year and 2 year columns do not mean drift in 1st and 2nd year. These are maximum errors with 1 year and 2 year calibration intervals.
Drift basically drops exponentially with time. After reference is 2-3 years old drift will be in low ppm range.
Other components will settle too.

temperance:
Also check the price for extra PC software if you need that. Tek's Kickstart software will cost you €177 annually or over €500 for a perpetual license. EasyDMM for a Signlent is free.

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