Rigol DS2000A calibration problem - Page 1
Forum section: electronics / testgear

author: Willi100
author_rank: Contributor
timestamp: July 22, 2014, 02:20:11 pm
content: Hello,I have a DS2072A with upgrade to DS2302 (300MHz)After upgrade I recognized that the low frequency and DC performance is not good as before. Therefore I did the Self Calibration. But the calibration did not help. The calibration makes it worse.For example:Test Signal: 1 MHz Sinus with 0dBm = 224mV RMSMeasured with Boonton RF- Millivoltmeter 92E:224mV RMSMeasured with DS2072A before upgrade:224mV RMS(@500ns)Measured with DS2072A after upgrade:227mV RMS(@500ns)After calibration I measured:233mV RMS(@500ns)My Questions:1. Is there any way to get the factory calibration back ? (Factory Reset....)2. Is there a possibility to control the internal (DC) voltage reference?3. Exists any Service Mode or Service commands ?Or any other ideas ?---------------------------------------------------Test gear:Signal Generator IFR2023BTRUE RMS RF Level Meter RACAL DANA 9303BOONTON RF Millivoltmeter 92E---------------------------------------------------Many thanks for helpWilli

author: David Hess
author_rank: Super Contributor
timestamp: July 22, 2014, 03:49:42 pm
content: What are the results if averaging is used instead of sampling? What about if bandwidth limiting is used?I would assume that with the higher bandwidth, more high frequency noise is being included in the oscilloscope's RMS measurement.The discrepancy between the Boonton and Rigol looks like it is within the combined accuracy of the two instruments. Just the Boonton by itself should only be within ( ( 300mV + 224mV ) * 1% ) = 5.24mV and the Rigol is worse than that.The Rigol's manual is depressingly sparse on the subject of measurement accuracy.

author: Willi100
author_rank: Contributor
timestamp: July 22, 2014, 05:32:34 pm
content: Hi David,Averaging or Normal: No differenceWith bandwidth limit: No difference (some times 1mV)I checked the measurement also with my Racal Dana TRUE Level Meter.The difference is stable. (I know both meters are accurate)It is not a measuring fault. The difference is real.Yes the deviation is not too much but before calibration it was perfect !I did also a measurement with a level calibrator output before upgrade and after upgrade + calibration.Have a look at the Pictures...

author: f1rmb
author_rank: Regular Contributor
timestamp: July 22, 2014, 06:26:40 pm
content: Hi,Quote from: Willi100 on July 22, 2014, 05:32:34 pmJust a little question, what kind of probe are you using ? (I'm seeing 50 Ohms input impedance selected in the screenshot).Cheers.---Daniel

author: Neddie
author_rank: Contributor
timestamp: July 22, 2014, 06:58:10 pm
content: Any chance the calibration has to be performed at a specific temperature?Neddie

author: Willi100
author_rank: Contributor
timestamp: July 22, 2014, 07:00:35 pm
content: RightIt's all 50 Ohm.The probes (at the Level-Meters) are special RF-Power sensor heads with 50 Ohm.You need it that you can measure the right RF-Level.WilliEdit: From the Signal-Generator there is a (50 Ohm) koax-kable direct to the scope input with 50 Ohm.

author: Willi100
author_rank: Contributor
timestamp: July 22, 2014, 07:06:12 pm
content: @ NeddieI play with that idea at the moment.But It's not a big deal....The much better way would be to change the intern voltage reference.Willi

author: JAmerican
author_rank: Newbie
timestamp: August 10, 2014, 08:51:43 pm
content: Quote from: Willi100 on July 22, 2014, 07:06:12 pmAny updates on this? Anyone else experience this issue?

author: JDubU
author_rank: Frequent Contributor
timestamp: August 10, 2014, 09:15:37 pm
content: I've noticed that the self calibration of my DS2072 seems to be better when I do it in an isolated, electrically quiet environment.I was initially running the self calibration within a few feet of other equipment (e.g. computer and monitor) and the baselines would end up being randomly off by a tiny bit relative to the baseline markers.

author: miguelvp
author_rank: Super Contributor
timestamp: August 10, 2014, 10:17:46 pm
content: Also allow for the device to warm up.I know my 2nd Channel takes longer to settle than Chan 1 for some reason.