Rigol DM3061 : Is this normal behaviour of this device? - Page 1
Forum section: electronics / testgear

author: good_cap/bad_cap
author_rank: Contributor
timestamp: March 08, 2013, 07:59:44 pm
content: Hi,i got a DM3061. The unit looks good and has been calibrated one year ago.However, if I power it on and switch to resistor measurement, diode test or continuity test, it shows false readings for the first few minutes.For example, with no leads connected, it outputs values between 1k and some megaohms.When I connect an 1 MOhm resistor, it still shows lower values. When I connect an 100 Ohm resistor, it shows about 100 Ohm.So it seems as if there is were an internal resistor.After some minutes, values go up until it displays "over range" (inputs open). It then works fine.Current and voltage measurements are not affected.Edit: Seems to happen when device is cold (room temperature is about 17°C). When room is warm, it takes less time to display correct values.Regards,gc/bc

author: cyr
author_rank: Frequent Contributor
timestamp: March 09, 2013, 03:28:08 pm
content: I don't know about the Rigol in particular, but it sounds faulty to me. It's normal for high-precision meters to require some warmup time to reach full performance but it should be usable straight away on all functions, and showing 1k measuring an open circuit sure isn't usable. I wouldn't trust it to be accurate even after warming up with that behaviour...

author: Unknown
author_rank: Unknown
timestamp: March 09, 2013, 03:45:04 pm
content: Agreed. The warm-up requirements are for the last 0.01% in accuracy, not for basic functionality. This is not a tube-era instrument.

author: PA4TIM
author_rank: Super Contributor
timestamp: March 09, 2013, 10:56:32 pm
content: Many tube equiped stuff does not need so much time as modern gear. My bontoon 63H manual talks about 2 minutes warm up. But I agree, gear needs about 2 hours foor the last ppm's not for something the topic starter writes.I have several 6,5 and 7,5 digit meters and when I switch them on, they are ready. Between powering up and 2 hours later, there is a few ( 10-20) mOhm difference or about 20-40 uV depending on temp and relative humidity in my lab.So i think there is something wrong in your Rigol, maybe a bad soldering that makes better contact while warming up.Is this fenomen started overnight or did it became intermittend and got worse over time ?Did you probed high voltage while in resistance or diode range ?Is the voltmeaurement correct from start.The resistance and diode mode usualy use the voltmeasure function and source current, through a volt or current source. If the voltmeasuring is correct the switching relais or source could be wrong.Ou could measure the output with an other meter. If that stays constant, and voltage meaurement function stays stable it must be a bad contact or soldering. I do not think it is a reference resistor because the diode function gives a problem too if I undrstand well.Rigol has 3 year warranty so I can not be worm yet, it should hold at least an other year until warranty is passed( just kidding, if you have warranty just return it, if not, open it and do ome tests. I it is a 6,5 digit work clean, remove flux after soldering, do not make fingerprints on the pcb ect and clean everything with IPA after repair. The dirt can cause leakage currents tht introduce faults ( not as big as what you have now)

author: good_cap/bad_cap
author_rank: Contributor
timestamp: March 10, 2013, 12:37:22 am
content: Hi,I got this unit cheap, so I don't know what the previous owner did to it.Yes, diode and continuity is affected, too.I now realized that there is something wrong with the 2V (DC) range, too:200 mV range is ok, it then switches to the 2V range.When I input more than 2 Volts, it does not switch to the 20V range, but outputs wrong values. I have to manually select the 20V range.Autoranging from 20V range to 2V and 200mV range works fine.So it seems as if it does not reach the upper "boarder" of the 2V range, which prevents it from switching to the 20V range.

author: good_cap/bad_cap
author_rank: Contributor
timestamp: May 02, 2013, 09:04:45 am
content: Rigol support was able to reproduce this behaviour. with their devices. They said it is "normal" because the units need about 30 minutes to heat up...I don't like that very much...

author: wraper
author_rank: Unknown
timestamp: May 02, 2013, 09:17:56 am
content: Seems that someone at Rigol support has good imagination how to get rid of a customer.