Products > Test Equipment

Keithley 2100,2000, etc or Chinese bench multimeters?

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KungFuJosh:

--- Quote from: tautech on October 28, 2024, 08:30:43 pm ---Yet EasyDMM is easier to use should you not have any programming skills.

--- End quote ---

Yes, EasyDMM is easier to use. It still sucks by comparison, and TestController doesn't need any programming skills if your device is already supported. You can program stuff/functions, but you don't need to.

Caliaxy:

--- Quote from: 2N3055 on October 28, 2024, 06:54:09 pm ---
--- 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.

--- End quote ---

I understand that :) I just inferred that if those maximum errors guaranteed by the manufacturer at delivery embed the drift of the reference (which, whatever it is, gets smaller with time) the lower degradation of accuracy in the second year after calibration reflects a one year longer-aged reference, right-shifted on its exponential curve. In turn, this would show a longer-aged reference in DMM6550 than in KS34665, for instance.

Of course, this doesn't mean I am not wrong. There must be other factors/components that make DMM6550 better than KS34465 and KS34665 better than KS34461 and SDM3065. And no instrument gets better by just aging...

What specs in the data sheets made you infer that KS34465 might have an aged reference (as opposed to KS34461 or SDM3065)?

Caliaxy:

--- Quote from: nctnico on October 28, 2024, 06:49:54 pm ---
--- 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.

--- End quote ---

Agree, I might make wrong assumptions. A 100 ppm drift would alter those specs, a 5 ppm would not.

nctnico:

--- Quote from: Caliaxy on October 28, 2024, 09:58:53 pm ---
--- Quote from: 2N3055 on October 28, 2024, 06:54:09 pm ---
--- 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.

--- End quote ---

I understand that :) I just inferred that if those maximum errors guaranteed by the manufacturer at delivery embed the drift of the reference (which, whatever it is, gets smaller with time) the lower degradation of accuracy in the second year after calibration reflects a one year longer-aged reference, right-shifted on its exponential curve. In turn, this would show a longer-aged reference in DMM6550 than in KS34665, for instance.

Of course, this doesn't mean I am not wrong. There must be other factors/components that make DMM6550 better than KS34465 and KS34665 better than KS34461 and SDM3065. And no instrument gets better by just aging...

--- End quote ---
Probably by selection. Keep in mind that Keithley / Fluke and Keysight have decades of know-how where it comes to making high precission multimeters and how to age / select references to meet specifications.

KungFuJosh:

--- Quote from: nctnico on October 28, 2024, 10:12:31 pm ---Probably by selection. Keep in mind that Keithley / Fluke and Keysight have decades of know-how where it comes to making high precission multimeters and how to age / select references to meet specifications.

--- End quote ---

It's not that simple. All these major brands know how to do that. The same question also applies to different meters within the same brand(s).

In theory, Siglent keeps the price of their bench DMMs lower by not spending the investment pre-aging the references. I don't know to what degree that's true, but that's what I've read. My SDM3065X has excellent stability, especially for it being so young. 😉

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