How much current will my arbitrary waveform generator provide (Siglent SDG1010) - Page 1
Forum section: electronics / testgear

author: Bigman
author_rank: Regular Contributor
timestamp: January 24, 2015, 03:52:07 pm
content: Hi,I am first time user of an arbitrary waveform generator. I am wondering, when I connect the Output of the generator to a circuit, how much current it will provide.Let's make an example:I am telling the generator to provide a constant 3V signal. I assume, the generator will then behave like a voltage source (keeping the voltage on a constant level, regardless of the current). If I would short-circuit the output, I ASSUME, the current would be something like 3V/50 Ohm=60mA. I choose 50 Ohm, because the datasheets says "Waveform Output Impedance 50ohm(typical value).Assuming instead of a short-circuit, I would connect the output with a small load of 30Ohm, would than my current be 3V/(50 Ohm + 30 Ohm) = 37.5mAThanks for you help!

author: TMM
author_rank: Frequent Contributor
timestamp: January 24, 2015, 04:25:19 pm
content: Yep, that's correct - you can treat it as a voltage source with a permanent 50ohm resistor in series with it's output.Most function gens are able to deliver short circuit current for at least some period of time. Be aware that when connected to a low impedance load, a significant amount of power can be dissipated across the 50ohm output impedance and depending on the design of the function gen it may overheat after some time - hopefully followed by the function gen automatically disabling it's output and displaying an overload message.

author: Bigman
author_rank: Regular Contributor
timestamp: January 24, 2015, 04:27:27 pm
content: TMM,thanks a lot for your kind and detailed reply. Highly appreciated

author: Electro Fan
author_rank: Super Contributor
timestamp: January 24, 2015, 06:16:16 pm
content: some 50 ohm feed through terminators are spec'd for 2 watts

author: nctnico
author_rank: Super Contributor
timestamp: January 24, 2015, 06:56:23 pm
content: It's not a problem to run the SDG1000 with a shorted output or low impedance load for a long time. No need to add extra series resistors. The output impedance/resistor is 50 Ohms already.

author: egonotto
author_rank: Super Contributor
timestamp: January 25, 2015, 03:23:08 am
content: Hi,Bigman wrote:"Assuming instead of a short-circuit, I would connect the output with a small load of 30Ohm, would than my current be 3V/(50 Ohm + 30 Ohm) = 37.5mA"The voltage on the output of the generator is then 1.125V = 30 Ohm*37.5mAMuch generators have therefore the settings "high impedance" and "50 Ohm"In setting "high impedance" you have 3V on the display. in setting "50 Ohm" you have 1.5V on your display. When you terminate the generator with 50 Ohm instead of 30 Ohm then display in setting "50 Ohm" is the voltage at the output.Best Regardsegonotto

author: tautech
author_rank: Super Contributor
timestamp: January 25, 2015, 06:00:05 am
content: Be aware Ch 2 does not have the drive capability of Ch 1.Recent tests for the "show us your squarewave" thread confirm this.Study of this post will show how Ch 2 risetime is faster at a reduced voltage.https://www.eevblog.com/forum/testgear/show-us-your-square-wave/msg589377/#msg589377This behaviour is not unusual for AWG's in this class.

author: rf-loop
author_rank: Super Contributor
timestamp: January 25, 2015, 07:40:14 am
content: In SDG1000 there is also variable adjustment for load impedance, not only Hi-Z and 50 ohm.And aswer to this "Topic: How much current will my arbitrary waveform generator provide (Siglent SDG1010)"(CH1) max ~200mA (Zload 0 ohm = short circuit)(CH2) max ~120mA (Zload 0 0hm = short circuit)

author: Bigman
author_rank: Regular Contributor
timestamp: January 25, 2015, 10:37:20 am
content: wow ... I wouldn't have expected that the "signal" input-impedance of my designed circuit has to match 50 Ohm, respectively, that I have to know exactly that input-impedance in order to feed my generator with this value. Is that reality: that all those engineers will calculate their circuit's "signal" input-impedance, before they turn-on the waveform generatorOn top of that. I have now the next issue: despite I am following the manual instruction, I cannot change that 50 Ohm value (see pictures attached).

author: tautech
author_rank: Super Contributor
timestamp: January 25, 2015, 11:42:09 am
content: Quote from: Bigman on January 25, 2015, 10:37:20 amUtitility button/Output setup

author: Bigman
author_rank: Regular Contributor
timestamp: January 25, 2015, 11:46:32 am
content: Quote from: tautech on January 25, 2015, 11:42:09 am.. that's exactly what I did and brings up the user-interface as shown in the picture above ... but there, I cannot change the 50 Ohm.,,,

author: tautech
author_rank: Super Contributor
timestamp: January 25, 2015, 11:50:39 am
content: Quote from: tautech on January 25, 2015, 11:42:09 amThen toggle the button adjacent...the one with the little line that lines up with the options on screen.

author: Bigman
author_rank: Regular Contributor
timestamp: January 25, 2015, 11:57:53 am
content: Quote from: tautech on January 25, 2015, 11:50:39 amI assume, you mean the button which I marked with a red circle. This just changes to High-Z (where I also cannot change the load value, see second attached picture).

author: tautech
author_rank: Super Contributor
timestamp: January 25, 2015, 12:12:26 pm
content: Asrf-loophas posted you have up to 200mA available into zero Ohms without damage.I can see no means to adjust the output load impedence, so I will hand you to the master for more info.It might be a case of RTFM but I'm too tired and time for bed.......

author: Bigman
author_rank: Regular Contributor
timestamp: January 25, 2015, 12:22:12 pm
content: Quote from: tautech on January 25, 2015, 12:12:26 pmFirst: thanks so far for your kind support. I am grateful for that.For my current situation, using HighZ is the way I can live with. Anyhow, I would like to understand how to use (and set-up) my wave generator also for the future.So, I may have to open a new thread, "how to adjust the 50 Ohm on a SDG 1010". I mean, my problem is: once in the future, I may have to adjust those 50 Ohm, and the manual says it can be adjusted ... but is the manual lying. Of course not ... but what I am doing wrong?Anyhow: again, thanks for your heldand sleep wellBTW: RTFM = Read the fucking manual,,, hey, that's exactly what I did ... I even posted in #8 the manual-page regarding this topic (regarding electronics, I may be not so proficient and need to learn a lot as a newbie. If it's really in the manual, than it looks for me like, Siglent only wants to sell their product to experienced users ....)

author: nctnico
author_rank: Super Contributor
timestamp: January 25, 2015, 12:39:35 pm
content: The can't adjust the 50 Ohm output impedance. That is fixed in the hardware. The only thing you adjust with the LOAD impedance setting is the amplitude scaling. You have to see the generator as a source with a 50 Ohm resistor in series. The actual amplitude depends on the load resistance.

author: Bigman
author_rank: Regular Contributor
timestamp: January 25, 2015, 12:48:00 pm
content: Quote from: nctnico on January 25, 2015, 12:39:35 pmnctnico, thanks for your reply.Indeed, that's what I already understood: by changing the 50 Ohm setting, I will "only" correct the voltage-numbers displayed on the generator. But despite the manual says, that I can put in a value different to 50 Ohm, it doesn't let me to do that.

author: rf-loop
author_rank: Super Contributor
timestamp: January 25, 2015, 12:52:05 pm
content: Quote from: Bigman on January 25, 2015, 12:48:00 pmWhat is your FW version?Old FW did not have this feature. This feature is added in latest FW Version: 1.01.01.36R1http://siglentamerica.com/gjjrj-xq.aspx?id=1188&tid=15If it ask you login:User name: publicPassword: siglent

author: Bigman
author_rank: Regular Contributor
timestamp: January 25, 2015, 01:04:25 pm
content: Quote from: rf-loop on January 25, 2015, 12:52:05 pmMy SDG1010 gives my following information:Boot strap number: 28Software version: 1.01.01.31Hardware version: 02-00-00-25-25Model: SDG1010Serial number: SDG00004130202Sine the FW from the link you provided is 1.01.01.36R1 and the info on the site from your link says "SDG1000 P36R1 version resolves the following issues: [...] 2. Add the variable impedance function [...]" --> a FW should solve my issue.After I will have done the FW-update, I will post the result here (may take an hour, I have to take lunch now)

author: Bigman
author_rank: Regular Contributor
timestamp: January 25, 2015, 01:56:40 pm
content: I have update the SDG1010 ... and it works. Now, I can adjust the 50 Ohm setting.Thanks to everybody who took the efforts to support me with this.