Rigol DS1022Z Generator performance - Square wave - Page 1
Forum section: electronics / testgear

author: MattM
author_rank: Contributor
timestamp: September 10, 2020, 03:00:25 pm
content: Dear All,I recently bought RIGOL DS1022Z Function generator. Its specs say that it should be able to produce a square wave signal with frequency up to 25 MHz.However, my generator seems to have a bit tougher time producing an actual square wave above 15 MHz (see attached photos).Has anyone, who owns 1022Z, encountered this behavior? Or if you own 1022Z could you, please, check whether the signal quality is about the same?Notes: Measured with 500 MHz 2GS/s scope (can be seen in the pictures).Thank you

author: hexreader
author_rank: Frequent Contributor
timestamp: September 10, 2020, 03:08:21 pm
content: Looks to me as though you forgot to provide 50 Ohm terminator at the scope end?

author: MattM
author_rank: Contributor
timestamp: September 10, 2020, 03:13:40 pm
content: Hi, no, the gen is set to HighZ and the amplitude set on the gen is 5Vpp. The scope would have seen twice as large signal if the gen had been set to 50R load.

author: tautech
author_rank: Super Contributor
timestamp: September 10, 2020, 03:21:26 pm
content: Quote from: MattM on September 10, 2020, 03:13:40 pmAll AWG signal source is 50 ohms.HiZ only changes the voltage level to match the expected load.For proper reproduction of the square wave it need have a 50 ohm load.Hunt out a thread here called 'Show us your square wave' for more/better understanding.

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 10, 2020, 04:00:56 pm
content: Quote from: MattM on September 10, 2020, 03:13:40 pmi think you should set your gen to 50 ohm instead of HiZ. if voltage level on your gen should match up whats shown on your dso, you have terminated your gen output, if you see twice, you forgot to put the terminator in... HiZ setting on gen if the gen's output is not terminated such as directly connected to a circuit to get twice the amplitude of a properly 50 ohm terminated line. for longer coax/connection, its only usefull for low KHz frequency application to get twice the amplitude. read up coaxial cable capacitance and its effect on signal bandwidth if not properly terminated... if you havent done so.. cheers.

author: MattM
author_rank: Contributor
timestamp: September 10, 2020, 04:06:07 pm
content: Thank you for the clarification and my apologies to hexreader.However, the 50R termination (in scope) didn't really make any change.Output: Generator output 2.5Vpp ("50R")Input: TDS640 w/ internal 50R terminationCable: huber-suhner enviroflex 400I've also checked the thread you suggested. Wuerstchenhund posted pictures of 25MHz signal from DG1062Z which looked similar,so I guess this is 'normal' for DS1000 series.Thank you

author: bd139
author_rank: Super Contributor
timestamp: September 10, 2020, 04:20:40 pm
content: As an ex DG1022Z owner, I can confirm this is normal behaviour.

author: MattM
author_rank: Contributor
timestamp: September 10, 2020, 04:22:58 pm
content: Thank you bd139

author: Grandchuck
author_rank: Super Contributor
timestamp: September 11, 2020, 02:42:22 pm
content: Here is the squarewave performance of a Siglent SDG2122X at 25 MHz. It is specified at 9 nanoseconds risetime.