[MOVED] function generator? - Page 1
Forum section: electronics / general

author: poulin76
author_rank: Newbie
timestamp: December 18, 2010, 06:02:17 am
content: I'm looking to buy an inexpensive function generator and have come across many options. this would be used in a hobby type setting. I've looked at the BK 4070A and the Rigol DG 1022 20M the closest and cannot decide if the Rigol would be worth the extra money or if there is something else out there better. thanks -Paul (Seattle, WA)

author: saturation
author_rank: Super Contributor
timestamp: December 18, 2010, 11:00:08 am
content: If its a hobby, are you sure you're ready for a $600 arbitrary waveform generator? The BK is discontinued, but at tequipment.net the replacement in an Instek. You can get the B&K used, on eBay in the $300-500 range.http://www.tequipment.net/InstekGFG3015.htmlThere are reviews on that Rigol on eevblog, its less that stellar.If you're just starting in electronics and need an FG, a new $150 1003 by Instek is DDS based, up to 3 MHz, with solid high quality signal generation.

author: rutri
author_rank: Newbie
timestamp: December 25, 2010, 07:36:38 pm
content: Quote from: saturation on December 18, 2010, 11:00:08 amHello,I have been looking at three different function generators, the Instek 1003, the Instek GFG-8216A and the BK 4003A. The Instek 1003 it looks alright but the triangle only goes to one MHz, there is no counter and no External Voltage Controlled Frequency (VCF) and there is no ramp function what is the VCF function used for and how often do you guys find its used. The Instek GFG-8216A has instability in the lower frequency range according to the review, if anyone knows if this has been fixed since review was done about a year ago, let me know please. The BK 4003A looks good however it is starting to get up there in price, is it worth the additional cost?

author: saturation
author_rank: Super Contributor
timestamp: December 28, 2010, 02:06:45 pm
content: The tradeoff is between test functionality of the analog FG over the quality of the waveform produced by the 1003.Triangle waves are rarely used today, but if you did it would be commonly to prototype or test PLL, PWM designs. 1 MHz is often good enough, but its still rarely used.For higher frequencies, quality low distortion sine, and fast rise time sq are important, a good sq wave at 3 MHz can do rough frequency response measurements up to the 9th harmonic, or1527 MHz.Frequency counter is often better not integrated into the unit, typically ones go to 1Ghz for $100. Also, the Rigol 1052E and many such scopes have fairly accurate counters built in.There's more to tell, but will get back when time allows.Quote from: rutri on December 25, 2010, 07:36:38 pm

author: rutri
author_rank: Newbie
timestamp: December 30, 2010, 06:16:27 am
content: Quote from: saturation on December 28, 2010, 02:06:45 pmI do have a Rigol scope, so I should be good for the frequency counter, however I am interested in doing a lot of work with PWM circuits. I am working on some hobby projects to drive some motors, and plan to control them using PWM's. That is the main reason why I will be getting the function generator The other reason is to test some code out using an ADC input on a few of my micros. Judging from what you were saying below my options are down to the BK 4003A or the Instek GFG-8216A. I really would like to know if there are any reviews out for the BK 4003A to see if there are any flaws or things to watch out for before I buy it.Thanks,Richard

author: saturation
author_rank: Super Contributor
timestamp: January 03, 2011, 10:37:48 pm
content: PWM can be emulated with square wave duty cycle adjustments on most FG.Frequency stability isn't so much an issue in most repair work. Electronic sweeps are timesavers but you can manually sweep frequencies as needed. However, the VCO can be very helpful in PLL design, but its most vital to have a stable frequency generator before a VCO input.A review of the B&Khttp://www.amazon.com/Precision-Sweep-Function-Generator-Digit/product-reviews/B00080FM1O/ref=dp_top_cm_cr_acr_txt?ie=UTF8&showViewpoints=1B&K stability 0.2% and distortion <=2% range, the waveforms are inadequate for audio analysis and can add difficulty when designing phase or frequency dependent circuits like PLL.

author: ionioni2000
author_rank: Newbie
timestamp: February 05, 2011, 10:47:01 am
content: Sorry to intervine...How about Instek GAG-810 Audio Generator, for someone who intend to used it only in audio work?http://www.testequity.com/products/1039/It says:500 Hz to 20 kHz, 0.02% or less, distorsion factor.Isn't it better than SFG 1003?Any other suggestions, on a buget?II

author: saturation
author_rank: Super Contributor
timestamp: February 05, 2011, 02:36:51 pm
content: Yes, much better at distortion at the audio range but not so good in the low bass range, under 100 Hz its 0.3%. But not sure if you can hear a distortion at that small difference.The trade off for low distortion in audio generators is far lower frequency stability and lower ranges for frequency generation, but those are not important issues for audio. To get a combination of high stability and distortion means costly equipment. For example a reference DDS type generator:http://www.thinksrs.com/products/DS360.htm,is about 0.001% in the audio range and runs $4000.See this thread too, it has more details and pictures:https://www.eevblog.com/forum/index.php?topic=1392.msg32213#msg32213From the link, here are some major spec differences,Instek 1003 is in green and an ! point:10 Hz to1 MHz, 5 ranges;! 3MHzFrequencyAccuracy ±(3% + 1Hz),! <20ppm, or .002%Distortion Factor500 Hz to 20 kHz, 0.02%or less,! ~0.18% 0.5 Hz - 3 MHz,100 Hz to 100 kHz, 0.05% or less50 Hz to 200 kHz,0.3%or less20 Hz to 500 kHz, 0.5% or less10 Hz to 1 MHz, 1.5% or lessSQUARE WAVERise & Fall Time Less than200 nS,! < 5nsDuty Ratio50% ±5%! +/- 90%For comparison, Tek SG505 is one notable audio generator, you can see the specs. It appears now and then on eBay from $100-200, but you also have to rig up its power supply properly, not just any power supply will do as it may inject noise into the electronics. Its harmonic distortion is rated at ~ 0.0008%, far better than the SRS.http://www.google.com/url?sa=t&source=web&cd=1&ved=0CBYQFjAA&url=http%3A%2F%2Fwww.testequipmentconnection.com%2Fspecs%2FTEK%2520SG5010%2CSG505%2520SPECS.PDF&rct=j&q=tek%20sg505&ei=qlhNTca-IoL7lwfm7r3pDw&usg=AFQjCNEof2zEgqsAKUOHSjKIYnlZh_hP0A&sig2=mxnDc5RHCbR-UrqhZrwbmA&cad=rjaThe question really now becomes, which is more important, distortion or stability?Most humans cannot hear distortion below 1% or ~ -40dB. The 1003 is specified 0.18% or - 55dB. Its not the best is you believe audiophiles can hear 0.1% or less. Here's a sample curve of distortion versus frequency on human hearing and is similar to academic hearing tests, extrapolating the X axis will show -55dB is out of range of human hearing:http://www.axiomaudio.com/distortion.htmlLastly, both Instek and Tek are very reputable, so you can believe its spec sheets are accurate. Note, the Instek 1003 might be a rebrand of an OEM of Quakko, but the Instek version is tested to its spec sheet, whereas the Quakko has more capability but unknown fidelity.Quote from: ionioni2000 on February 05, 2011, 10:47:01 am

author: ionioni2000
author_rank: Newbie
timestamp: February 09, 2011, 01:34:13 pm
content: Many thanx,saturation!It is all more clear for me, now.Thank you, again.II

author: saturation
author_rank: Super Contributor
timestamp: February 09, 2011, 03:32:50 pm
content: you're welcome. You may want to see the Hantek 3x25 thread for a very cost effective function generator that goes on eBay for ~ $150.Quote from: ionioni2000 on February 09, 2011, 01:34:13 pm

author: Unknown
author_rank: Unknown
timestamp: February 09, 2011, 04:40:40 pm
content: Quote from: saturation on February 09, 2011, 03:32:50 pmBut from what I gathered from your comments (please correct my if my understanding is incorrect), you wouldn't recommend this one over the Instek SFG-1003 if you want quality over quantity (eg. clean output over extra frequency range and arbitrary waveform ability). If someone is considering a dedicated audio frequency generator for low distortion, the Hantek doesn't seem the most obvious choice to me. Plus I think a real front panel is much nicer to work with than a computer screen with 'fake knobs'. Not as much an issue with arbitrary waveforms, since you wouldn't want to input those points manually anyway, but I think it would be inconvenient for basic sines/sweeps.

author: saturation
author_rank: Super Contributor
timestamp: February 10, 2011, 09:28:27 pm
content: Yes, alm, you're right. Sorry to the OP, but was not tracking his name. I'd concur the 3x25 is at least, undefined for use in quality audio work.Quote from: alm on February 09, 2011, 04:40:40 pm