HP/Agilent 8648C Signal Generator - Page 1
Forum section: electronics / testgear

author: eurofox
author_rank: Unknown
timestamp: October 16, 2013, 04:27:01 pm
content: Hi,I just won this instrument on ebay but one big knob is missing.Somebody know where I could buy this?Thanks,eurofox

author: sync
author_rank: Frequent Contributor
timestamp: October 16, 2013, 04:38:56 pm
content: Agilent? They sell spare parts.

author: eurofox
author_rank: Unknown
timestamp: October 16, 2013, 05:04:57 pm
content: Quote from: sync on October 16, 2013, 04:38:56 pmI already send them an email but since this instrument is obsolete I'm not sure that those parts are available in Europe.My idea to post it here was that maybe some members got a dead generator or they know a place specialized in Agilent spare parts.eurofox

author: KJDS
author_rank: Super Contributor
timestamp: October 16, 2013, 05:10:12 pm
content: I've probably got one. I'll check what the postage cost is tomorrow.

author: eurofox
author_rank: Unknown
timestamp: October 16, 2013, 05:17:01 pm
content: Quote from: KJDS on October 16, 2013, 05:10:12 pmHello KJDS,Thanks in advanceI really apprecialte it, just PM me with your price + shipping cost and paypal email.With kind regards,eurofox

author: ted572
author_rank: Frequent Contributor
timestamp: February 10, 2014, 04:00:33 am
content: I have two HP-8648C questions:1. If I enter a frequency with a higher resolution than 10Hz, such as 100.123,456,7MHz, is there any way to see it after it is entered to verify that it is what was entered? As the normal display is limited to 10Hz, and therefor the display would show this example as 100.123,46MHz. There must be a way to recall the full frequency information, but I haven't found it in the manual.BTW the specification is that you can enter a frequency with a resolution of down to .001Hz, but the resulting display is limited to 10Hz.2. My HP-8648C (with Option 1E5) has a frequency coverage of 100kHz to 3,200MHz (with 14dBm output over the whole range), where as the newer units cover 9kHz to 3,200MHz (but with 13dBm output up to ~2,000MHz, and then 10dBm up to 3,200MHz) . Does anyone know how to differentiate the two versions of 8648C Sig Gens. The model number doesn't do it, so is there a unique 'Part number', or is it simply by 'Serial number', and if so what is the grouping of the serial numbers for 100 kHz vs. the 9kHz for the lower starting frequency?Thank you for any assistance, ted572

author: eurofox
author_rank: Unknown
timestamp: February 10, 2014, 01:09:29 pm
content: Quote from: ted572 on February 10, 2014, 04:00:33 amHi,My unit cover from 9 khz to 3,2 ghz with high stability and high power options.I never try, I could test it with my Agilent 53131A with as well high stability option and up to 3ghzI specify the options because for such test you need precision to validate it.I should run minimum one hour to get the oven's on temperature but I have no time to do this now.A quick test entering:1.111 111 111 Mhz I get on the frequency meter :1,111,111,3xx (xx not stable)I hope this answer your question,eurofox

author: ted572
author_rank: Frequent Contributor
timestamp: February 10, 2014, 02:31:13 pm
content: Quote from: eurofox on February 10, 2014, 01:09:29 pmHi,My unit cover from 9 khz to 3,2 ghz with high stability and high power options.I never try, I could test it with my Agilent 53131A with as well high stability option and up to 3ghzI specify the options because for such test you need precision to validate it.I should run minimum one hour to get the oven's on temperature but I have no time to do this now.A quick test entering:1.111 111 111 Mhz I get on the frequency meter :1,111,111,3xx (xx not stable)I hope this answer your question,eurofoxTo: eurofox, From: ted572Thank you for the quick reply, but no this does not answer my question #1. I had also verified that the input frequency does work, although maybe not perfectly that well down to .001 Hz due to a minute amount of residual FM on the 8648's carrier frequency. What I'm after; is it possible to verify that the correct frequency was entered when a resolution of better than 10Hz was entered. I don't really need this capability from my generator, but I'm curios as to why the capability is there if the value can't be verified from the generator itself.I also have an accurate (disciplined) Frequency Standard* that is within +/- 3 to 5 parts per 10 to the -12, so that is how I verified that the generator does indeed do fairly well at .001Hz resolution (* with the Freq. Std. driving both the 8648C and my counter).So to recap my questions:1. Is there anyway you know of to pull up, or recall the whole freq. on the 8648 without being limited to the normal Freq Display that is limited to 10Hz resolution? Again I don't need to do this, I just would like to know if there is a way, and if so how.2. How is your 8648C that starts off at 9kHzdistinguished from my unit by HP( P/N, S/N, etc. ?) that starts off at 100kHz?Thank you eurofox for your assistance. Cheers, ted572

author: Neganur
author_rank: Unknown
timestamp: February 12, 2014, 07:34:34 am
content: Quote from: ted572 on February 10, 2014, 04:00:33 amIIRC you can read the frequency register with HPIB:* Connected to: GPIB0::19::INSTR-> FREQ:CW?<- +1.00000000000000E+008When I enter 1.234567890123 MHz from the front panel, and read the frequency with HPIB (GPIB) I get:-> FREQ:CW?<- +1.23456789012300E+006my unit is the HP8648BEDIT: heh, I just noticed that that's much more than 0.001 Hz resolution.Just for the hell of it, I also entered 9.123456789012 kHz and get:-> FREQ:CW?<- +9.12345678901200E+003

author: ted572
author_rank: Frequent Contributor
timestamp: February 12, 2014, 11:40:28 am
content: Quote from: Neganur on February 12, 2014, 07:34:34 amThank you, that is very interesting. What application are you using to talk to the Sig. Gen. via GPIB? When you referred to using HPIB, is this HP Instrument Basic? Is there a way to simply use a text file to communicate (send and receive commands) with it?Thank you for the assistance, ted572

author: eurofox
author_rank: Unknown
timestamp: February 12, 2014, 11:47:08 am
content: I use the Agilent connection expert for basic testing and communication.I think by using Labview it should be possible to decode the data and put it in "real" frequency.I just wonder if it is really usefuleurofox

author: Neganur
author_rank: Unknown
timestamp: February 12, 2014, 12:42:09 pm
content: Quote from: ted572 on February 12, 2014, 11:40:28 amI used just the "Agilent Interactive IO" console from the "Agilent Connection Expert" (software that handles VISA).Sorry for being ambiguous with the initialism "HPIB", I meant theIEEE-488 General Purpose Interface Bus(developed by HP, adopted as de facto instrument control standard).Depending on the controller you can talk to and control instruments that support it directly, with for example a C program, python, HTBasic (HP-Basic) If your controller supports VISA, you can also use Labview or Matlab etc. Ebay has sometimes cheap (or not so cheap) PCI GPIB cards from Agilent or National Instruments. The now outdated Agilent 82357A USB/GPIB works well too. Then there's Prologix or EEVBlog user scasagrande who make their own little controller. If I'm not mistaken, I've read that someone recently used an Arduino to talk to an instrument.The arduino or the controller that scasagrande make may be affordable and simple enough for what you're looking for. If you have the money to fool around with Labview etc, it's probably best to get a proper (used) Agilent controller since VISA can be a pain to get working without the documentation available from those folks. Other people may have experience with that, I'm just a user in that regard.Beware, the cables can be stupidly expensive. Sometimes there's a steal.

author: bingo600
author_rank: Super Contributor
timestamp: February 12, 2014, 02:14:12 pm
content: The Beiming USB gpib is Agilent. Ccompatible, and quite good.http://www.ebay.com/itm/S82357-GPIB-USB-interface-Agilent-82357B-compatible-/171236377955I use it as much as my Agillent USB adapter./Bingo

author: ted572
author_rank: Frequent Contributor
timestamp: February 12, 2014, 02:26:25 pm
content: Quote from: Neganur on February 12, 2014, 12:42:09 pmThank you Neganur for the details. I'm not really interested at this time in spending the money or energy to invest in GPIB again. I used to have the cables, computer hardware interface software, but got rid of it a long time ago due to no longer needing it. As I used to design ATE hardware and software (in HP Instrument Basic, and MS C++) for controlling our DUT (military radio) and all of the corresponding test equipment for manufacturing module level and final product testing.I very surprised that HP didn't truncate the manual frequency input to the hp-8648 to .001 Hz, or even 10Hz. The way it is now if you add a digit or so beyond 10Hz resolution you won't necessarily know it from the front panel display, unless of course the results get rounded up to affect the 10Hz value. It' also surprising that you can input a frequency beyond .001Hz. What were they thinking?Thank you for for your suggestions.