HP 34401A data via RS232 and GPIB to two computers - Page 1
Forum section: electronics / projects

author: enut11
author_rank: Super Contributor
timestamp: January 08, 2023, 08:17:34 pm
content: Is it possible to send data to 2 computers (not simultaneously) via USB from a HP 34401A, one connected to the RS232 port and the other connected to GPIB on the DMM?

author: Andreas
author_rank: Super Contributor
timestamp: January 08, 2023, 10:26:01 pm
content: I fear no.You have to select either RS232 or GPIB from the menue.with best regardsAndreas

author: enut11
author_rank: Super Contributor
timestamp: January 09, 2023, 12:30:17 am
content: Thanks Andreas.If I select, eg GPIB from the 34401 menu, can I leave the RS232 cable plugged into the 34401 but not used (and vice versa)?enut11

author: bdunham7
author_rank: Super Contributor
timestamp: January 09, 2023, 12:46:27 am
content: Quote from: enut11 on January 09, 2023, 12:30:17 amIf you are asking if you can attach both cables and then stuff your meter up in an inaccessible rack and just use one cable or the other without disconnecting anything in the back, yes, you can do that. But of course you'd have to go poking through the menu to change the communication status each time.

author: enut11
author_rank: Super Contributor
timestamp: January 09, 2023, 06:16:50 am
content: Yes, that is exactly what I would like to do. Just wanted to be sure that it would not damage the meter.Thanksenut11

author: Kleinstein
author_rank: Super Contributor
timestamp: January 09, 2023, 10:29:41 am
content: Chances are the ground of the RS232 and GPIB is linked. So one would create a ground loop between the 2 computers (if they are grounded and not laptops). This could make the setup slightly more sensitive to a lightning strike, but such things happen from time to time anyway, especially with RF gear. It would be good if both computers would be powered from the same (or linked) outlet.In the old times with Comodore PET we even had 2 computers sharing a floppy drive and printer connected via GIPB - both connected at the same time, just make sure not to use at the same time.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 09, 2023, 01:01:47 pm
content: unless you use an fully opto isolated rs232 adapter, "fully" mean no common ground, some of them exists ....

author: artag
author_rank: Super Contributor
timestamp: January 09, 2023, 02:30:37 pm
content: Quote from: Kleinstein on January 09, 2023, 10:29:41 amI guess you could do the same with either computer being able to master the GPIB.

author: Andreas
author_rank: Super Contributor
timestamp: January 09, 2023, 07:38:57 pm
content: Quote from: Kleinstein on January 09, 2023, 10:29:41 amHello,This already happens if you connect the 34401A to one single computer.GPIB and RS232 are connected to mains earth and housing of the 34401A.In the computer RS232 and GPIB are connected to mains earth.If you have any monitor or other peripherals they build another ground loop ...So ground loops on the earth referenced side of the 34401A are normal.The tip with the same outlet is ok. (and should be common sense in a lab environment).But the isolated RS232 adapter breaks only one of the many ground loops.with best regardsAndreas

author: rcjoy
author_rank: Regular Contributor
timestamp: January 09, 2023, 08:56:50 pm
content: Quote from: artag on January 09, 2023, 02:30:37 pmAnother (more complicated) idea is to use a GPIB to LAN adapter (such as the Agilent/Keysight E5810A/B) , then two computers can connect to the meter via ethernet.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 10, 2023, 12:51:36 am
content: Good oneTo complicate thingsI think you have serial to gpibhttps://accusrc.com/uploads/datasheets/3817_GPIB-232CT-A.pdf

author: DavidKo
author_rank: Frequent Contributor
timestamp: January 10, 2023, 07:16:15 am
content: What about using one shared file and read it from multiple computers?

author: enut11
author_rank: Super Contributor
timestamp: January 10, 2023, 06:49:17 pm
content: What I currently have is an RS232 to USB (CH340) and an Agilent GPIB to USB converter.Both are connected to the HP34401A but only one is connected to a computer USB port at any one time. The unused interface is left unconnected at the computer end.One computer is a desktop and the other is a laptop.enut11

author: DavidKo
author_rank: Frequent Contributor
timestamp: January 11, 2023, 06:59:16 am
content: In your case it should be easy to isolate devices from computer. You can use USB isolator (it has DC-DC isolating converter to pass the power to device from computer). There are plenty of them, so you can choose what corresponds to your needs (I expect, that 12Mbps will be good enough, there are also 480Mbps, but they are not so cheap).