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[疑难问题] DS213 gain calibration

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发表于 2019-7-1 19:08:48 | 显示全部楼层 |阅读模式
Hi.

How do you calibrate the gain of a channel?

The K4+K3 combination calibrates the ground level.
Rotating the dial A while "CAL" option is selected will only shift the entire range, but doesn't change the gain.
Effectively, it is the same as ground level shifting.

The voltage measured are alwas off by some fixed value, and if I try to compensate it by rotating A dial with "CAL" option, I would also shift the zero.

What's the correct method of scope calibration using external voltage sources?


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发表于 2019-7-2 15:32:37 | 显示全部楼层
You use DS203 or DS213?
DS213 is auto calibrate, no need choice "CAL"
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 楼主| 发表于 2019-7-2 16:47:26 | 显示全部楼层
It's DS213.

It does something when calibrating, but what's the procedure?
Shorting the probe? Connecting to own signal generator output?
Any ways to use external precise voltage source?

In any case, the measured values are always somewhat off from the known source voltage.
And performing auto calibration without correct procedure makes the next measurements even worse
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发表于 2019-7-5 09:28:12 | 显示全部楼层
The channel gain of the DS213 is fixed.
No calibration is required.
‘CAL’ is used when auto-calibration fails in extreme cases and is only used for zero calibration.
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 楼主| 发表于 2019-7-5 17:21:51 | 显示全部楼层
Well, that's not really good.

My multimeter and lab PSU agree pretty well on the voltages. Say, 3.3 v selected. The DS213 measures 3.08v.
For 2.5v source DS213 measures 2.34v, and for 1.8v source DS213 measures 1.68v.
The observed scale is pretty much the same, ~0.9333

It's understandable that scaling the values for the waveform takes precious clock cycles, but at least the summary values shown in the bottom row (Vmax, Vmin, Vp-p,  /etc) could be scaled. They don't update very frequently, so scaling it wouldn't hurt the performance.
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发表于 2019-7-8 10:40:49 | 显示全部楼层
The next version will add a new feature (gain calibration for users to accurately measure voltage)
In addition, oscilloscope sampling is affected by input signal ripple, probe matching, etc. It is not recommended for accurate voltage measurement.
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