Agilent 33120A pissy square wave? - Page 1
Forum section: electronics / testgear

author: echen1024
author_rank: Super Contributor
timestamp: January 28, 2014, 06:16:26 pm
content: I was playing around with my 33120A function generator, andholy hellthat is a shit square wave. I think even the MHS2300 in the other thread does a bit better than this.Look at this 1MHz squarePretty decent at 500HzAnd you do NOT need to see 4MHzOthers with a function gen, can you verify that that yours does the same as well? And 10MHz, near the 15MHz limit is just a sine wave.

author: sync
author_rank: Frequent Contributor
timestamp: January 28, 2014, 06:21:53 pm
content: Do you have it proper terminated? 50 ohm BNC cable and 50 ohm terminator at the scope.

author: echen1024
author_rank: Super Contributor
timestamp: January 28, 2014, 06:22:16 pm
content: Yes I believe I do.

author: RRobot
author_rank: Regular Contributor
timestamp: January 29, 2014, 05:51:04 am
content: Hooked up to a MSO7034B my 33120A produces virtually no overshoot even at 4 MHz, provided I have the scope set to 50 Ohm impedance. Setting it to 1 Meg impedance the output looks similar to yours, although not quite as exaggerated. So basically you have not setup your impedance matching correctly.

author: AndyC_772
author_rank: Super Contributor
timestamp: January 29, 2014, 07:47:20 am
content: I see results almost identical to yours if I connect a probe to the the output of my function generator but don't connect the ground lead.If I use a BNC cable, I get a nice clean square wave whether I have the scope set to 50 Ohm or 1M.I think your problem is poor grounding, not impedance matching.

author: TiN
author_rank: Super Contributor
timestamp: January 29, 2014, 01:29:43 pm
content: Captured output on mine HP 33120A (was bought broken, replaced bunch of chips in it).Tektronix CSA7404 with TCA-BNC adapter on input (50 ohm only)1m BNC-BNC cable from front panel output on 33120A (tried also Tektronix SMA-SMA cable with BNC-SMA adapter on gen output and TCA-292MM adapter on scope)2.5 Vpp, 500Hz1 Vpp, 1MHz square wave mode2.5 Vpp, 1MHz square wave mode2.5 Vpp, 4MHz square wave mode2.5 Vpp, 15MHz square wave mode5 Vpp, 15MHz square wave mode

author: BravoV
author_rank: Super Contributor
timestamp: January 29, 2014, 01:42:10 pm
content: Quote from: echen1024 on January 28, 2014, 06:22:16 pmDunno why, I have doubt if you're not doing that properly, take a photo of your scope's coax cable connection picture right at the bnc and post it here.You are not using the scope probe, right ?

author: echen1024
author_rank: Super Contributor
timestamp: January 29, 2014, 04:10:06 pm
content: I am using a BNC cable I bought from weirdstuff.

author: rdl
author_rank: Super Contributor
timestamp: January 29, 2014, 04:13:58 pm
content: Doesn't that Rigol scope have 1 M ohm input? Are you using a 50 ohm adapter?

author: echen1024
author_rank: Super Contributor
timestamp: January 29, 2014, 04:20:43 pm
content: Godddamn it!I need a 50 Ohm adaptor now.

author: BravoV
author_rank: Super Contributor
timestamp: January 29, 2014, 04:49:40 pm
content: Quote from: echen1024 on January 29, 2014, 04:20:43 pmLOL ... I knew it, trap for young player as Dave says.Ideally you need a feed thru 50 ohm adapter, but a bnc T connector and a ordinary 50 ohm terminator should be fine since its easier to source and cheaper too.

author: linux-works
author_rank: Super Contributor
timestamp: January 29, 2014, 05:00:35 pm
content: since you're local to the bay area, go over to halted (hsc) and grab a tee and a 50ohm term.we know what the problem was. we all have done this before, not to worry

author: BravoV
author_rank: Super Contributor
timestamp: January 29, 2014, 05:31:46 pm
content: Quote from: linux-works on January 29, 2014, 05:00:35 pm+1Just to make sure you understand and not buying wrong stuffs, get one of this terminator with value of 50 Ohm, beware not the one with 75 Ohm termination, usually it has the number 50 Ohm printed at the cap like below example.Plug the 50 Ohm terminator at one end of that bnc T connector, while the middle male connector goes to your scope's BNC input, and connect the other end through the BNC cable to your fun-gen bnc output.

author: echen1024
author_rank: Super Contributor
timestamp: January 29, 2014, 05:54:33 pm
content: Quote from: linux-works on January 29, 2014, 05:00:35 pmI'm not. I was visiting. I'm in Texas. I will buy one off of Digikey or eBay then.

author: bingo600
author_rank: Super Contributor
timestamp: January 29, 2014, 06:58:13 pm
content: I saved some old T's and terminators from my first home cheapernet "10-Base 2"They come in handy now ....https://en.wikipedia.org/wiki/10BASE2If i see a couple of feed throughs for a nice price i'l grab some.But until then , this works ok./Bingo

author: linux-works
author_rank: Super Contributor
timestamp: January 30, 2014, 03:40:27 am
content: yes, the old DEC thin-net (10base2) tee and terminator finally come in handy again, after all those years

author: RRobot
author_rank: Regular Contributor
timestamp: January 30, 2014, 04:17:01 am
content: Quote from: bingo600 on January 29, 2014, 06:58:13 pmYes I've been looking for a few of these (specifically the Pomona 4119-50) on ebay as I can't bring my self to pay $50 for a new one. So far no luck.