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| Rigol DM3068 Calibration |
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| Kleinstein:
--- Quote from: alm on February 27, 2022, 07:37:57 pm --- --- Quote from: tautech on February 27, 2022, 10:09:02 am ---OTHO if it fails, then adjustment may be required and much modern equipment requires a universal calibrator controlled by a PC script to automatically check accuracy and make the SW adjustments. Some Cal labs have such equipment and the manufacturers calibration script however those that don't have access to scripts can write their own providing they have adequately trained and capable staff. --- End quote --- And assuming the manufacturer publishes documentation about the adjustment procedure. Rigol is the only major bench DMM manufacturer that doesn't publish this information. I find this ridiculous. Adjustment are not necessarily only happening if the unit fails its performance verification. That's something the customer can specify. Some customers might require adjustment to as close as possible to nominal, or to within its 24 hour specs. Good luck sending it to Rigol every time ;) --- End quote --- If you need accuracy near the 24 hour or even 3 month specs, than the rigol meter is the wrong instrument. Getter a high grade meter and do calibration less frequent. There could still be cases when a rather frequent calibration is needed. However this would not be because of high accuracy, but more because of high costs from failure. This may still be a reason for a better meter, or maybe run 2 meters in parallel. There is no absolute need to have the adjustment published. As long as the certified cal labs get the procedures or scrips, all would be fine. Frequent adjustment may make it hard to follow the drift / cal history. It depends on the way the adjustment is done: Ideally one would get the exact adjustments made. If done as a direct adjustment to measured values (external reference point), one may not get accurate factors to reconstruct a cal history without extra errors (e.g. noise of measurement and standad). In many cases there is still the option to not adjust the meter, but apply correction factors to the date one the PC side after the measurement. This even works backwards for data just before a calibration. |
| Kean:
--- Quote from: slugrustle on February 27, 2022, 04:24:04 pm ---I'm asking this question because of the two statements below from the service guide that also appear in the original post: --- Quote ---To ensure accuracy, the meter should be completely recalibrated when the interval is reached whatever interval is chosen. Even though the meter has passed the performance test, the specifications (see “Specifications”) cannot be guaranteed unless recalibration is done. --- End quote --- --- End quote --- The mention of "performance test" in the above quote appears to be referring to the end-user checks listed in section 2 of the service guide (self-test, fast test, & routine test), and it is saying that even if those end-user tests pass you should have professional calibration (verification) done at regular intervals. The mention of "recalibration" here can be misleading, and doesn't specifically mean adjustment (as others have indicated). |
| slugrustle:
Here's what Rigol came back with, quite similar to what people in this thread have been saying, so thanks for that. --- Quote ---3rd-party calibration is possible and preferred - our recommended partner is Transcat. They would be able to provide the certificate of calibration that would be good for a year or more depending on the standard you are conforming to. They can provide you a calibration price if you request a quote. The only time it would need to be sent to us directly is if it has failed calibration and requires repair/adjustment. --- End quote --- The manual also says, under the section "Routine Test" --- Quote ---The meter passed the routine test must be tested again when the test time interval is exceeded. The meter failed to pass the routine test must be calibrated or repaired before it is put back into use. --- End quote --- This part matches very well with routine test = verification, what people in this thread are saying, and how Rigol replied via email. The quote below, which really confused me, might simply be referring to the 24-hour and 90-day specifications based on what alm and Kleinstein said. If that's the case, then it all makes sense. I'd be happy if this thing performed half as well as the 1-year spec over the long term. --- Quote ---To ensure accuracy, the meter should be completely recalibrated when the interval is reached whatever interval is chosen. Even though the meter has passed the performance test, the specifications (see “Specifications”) cannot be guaranteed unless recalibration is done. --- End quote --- |
| slugrustle:
Unfortunately, I have a DM3068 purchased in July of last year that was just out of spec on a few ranges last time it was calibrated in December or January. I contacted Rigol, and it took four emails to get them to help me out; the first three responses only said they don't do calibration, their outside partners do. I said up front that the meter failed calibration and I wanted it adjusted back into specification. The meter was under warranty, so they gave me an RMA and I shipped it in. They replaced the mainboard. I just received the unit back, and they did not include a calibration certificate of any kind. I'm guessing they just replaced the mainboard and ran self test. I'm following up with them on this because it's unacceptable. It's like they don't even understand what these meters are for. The whole point in buying one is to get a device that measures within its specifications. That was also the whole point of me sending it back. Mindboggling. As a Rigol owner, I highly recommend either Keysight or Tektronix for bench DMMs. |
| J-R:
I'm curious, was the company doing the calibration not able to adjust it back into spec? Or they could, but it was more money so you wanted Rigol to cover it since it was so new and under warranty? |
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