Rigol DS2000 gave up with only 50 volts tt on entry... - Page 1
Forum section: electronics / testgear

author: Wim13
author_rank: Frequent Contributor
timestamp: March 22, 2014, 12:24:48 pm
content: I have a Rigol DS2000, according to the manual it can accept 300 Volts on a signal input.I was looking at a 50 Volts tt sinus around 100 Mhz over dummyload of 50 ohms, 5 divisions on the 10 volt position.Then suddenly the signal disapears, and my CH1 input at the DS2000 was past away....The entry was changed from 1 Mohm to 800 Mohm, and all signalswere after the disaster about 40 dB down. All functions of the input where still thereonly 40 dB down.So it is back to Rigol for repair, but are there any experiences around, on this issue,what does it mean that the entry can go for 300 Volts.., and die at 50 Volts.Because if it has been repaired, can i still trust this Rigol at high voltages..or is 50 volts to much for these modern DSO´s...

author: cyr
author_rank: Frequent Contributor
timestamp: March 22, 2014, 12:53:55 pm
content: 300V doesn't mean 300V at 100MHz.Scopes (and probes) generally have frequency derating specified, not sure if rigol does this but here is the Agilent DSO-X 3000 spec as an example:" 300 Vpk until 40 kHz. Then de-rates at 20 db/dec until 6 Vpk "

author: hans
author_rank: Super Contributor
timestamp: March 22, 2014, 12:54:07 pm
content: The scope has 13pF - 19pF input capacitance, parallel to 1MEG. This means that the input impedance will drop over frequency.If you're measuring at 100MHz, the impedance of that "capacitor" is only 132 ohms. If you're putting 50Vpp on it, which is 17.7V RMS, that's a lot of power (over 2W in fact).The 300Vrms rating could as well be at 50Hz, not 1MHz.

author: mjkuwp
author_rank: Unknown
timestamp: March 22, 2014, 01:02:30 pm
content: just a question; was the probe set at 1X or 10X

author: Wim13
author_rank: Frequent Contributor
timestamp: March 22, 2014, 01:20:40 pm
content: There was no probe, just direct on the back of a dummyload.In the manual of the Rigol , there is nothing about how to calculate the maximun Voltage.Only remarks about Cat II.Well if i look at the diagram below, ( from an other post in this forum ), there should be a limiting resistorin the entry.., perhaps some luck only this resistor is gone...

author: han
author_rank: Frequent Contributor
timestamp: March 22, 2014, 01:27:34 pm
content: Quote from: Wim13 on March 22, 2014, 01:20:40 pmCAT IICAT II defines circuits which are intended for direct connection into mains sockets or similar points. The energy in such installations should be limited to below 100 A continuously (or below 500 A for voltages not exceeding 150 V).The maximum available continuous power must be limited (for instance by a circuit breaker) to not more than 22 000 VA.Example: a device connected to a 240 V mains socket with 13 A fuse (energy limited to 3100 VA)fromhttp://en.wikipedia.org/wiki/Measurement_categorythe line freq surely not 100MHz

author: Wim13
author_rank: Frequent Contributor
timestamp: March 22, 2014, 01:31:32 pm
content: Yes i understand the Cat II,But i still cant find the maximum voltage input at 100 Mhz...in the manual

author: cyr
author_rank: Frequent Contributor
timestamp: March 22, 2014, 01:39:24 pm
content: Rigol don't seem to provide this information for the actual scope inputs, but they do have derating curves for their probes. For the RP3300 it seems that the limit at 100MHz is about 10Vrms (in 10X mode I would asume).

author: Rory
author_rank: Frequent Contributor
timestamp: March 22, 2014, 06:26:12 pm
content: Oops!Sorry to hear of your misfortune.So many scopes and frequency counters get shelved in the storeroom or sent off for repair for lack of these:http://www.birdrf.com/Products/Components/Variable-Signal-Samplers/4275-Series_20-1000-MHz-Variable-RF-Signal-Samplers.aspxhttp://www.birdrf.com/Products/Attenuators.aspxYou can make your own...I make it a habit to put a 10:1/20dB attenuator between my 'expensive' test equipment and rest of the RF world. They're easier and cheaper to replace.

author: Wim13
author_rank: Frequent Contributor
timestamp: March 25, 2014, 07:29:38 pm
content: So my DSO is repaired, luck, only the entry resistor was fried, see diagram above..the Rigol dealer here in the Netherlands, ArBenelux did not charge me.There is no Voltage limit graph in the manual, only with the probe.I put 18 Volts rms direct on the entry, no probe, as for the probe 14 V is the limit.So be carefull....

author: VK5RC
author_rank: Unknown
timestamp: March 25, 2014, 11:03:22 pm
content: I hope Rigol do the right thing, I have heard that a dc block is also a bit of insurance for expensive gear,