Connecting various lab instruments to ethernet

I have an assortment of lab instruments that I’d like to control from a PC. They have a range of connection options: RS232, USB, GPIB, Ethernet and support the SCPI protocol. Decided to standardise on Ethernet.

The three Rigol devices all have Ethernet connectivity so I assigned them all fixed IP addresses via the front panels, plugged into the LAN, and then connected via telnet (putty) to port 5555.

Rigol DP832

Responded to *IDN? query OK

Rigol DS1054Z

Responded to *IDN? query OK

Rigol DSA815

No reply to *IDN? query. I suspected the DSA815 did not like the CRLF line termination from putty and sure enough, sending just a LF terminator (0x0a) from a simple test program worked OK.

The other two older machines did not have an Ethernet port, so I connected via two Ethernet/RS232 adapters. I used the USR-TCP232-2 module from eBay. This doesn’t provide any hardware flow control so will need to bear that in mind for the PC control software.

The instructions were not the clearest but in the end configuration was straightforward. Plug the device into the LAN and run the USR-TCP232-T24V5.1.0.1.exe setup program. Click “Search in LAN” and you should see your device in the list. Select “TCP Server” mode, give it a new IP address and set the subnet mask and default gateway for your router. Set the module port to 5555 to match that used by the Rigols. Configure the RS232 port as needed. Then click “Set selected item via LAN”.

Keithley 2015 THD

Set RS232 comms to 19200,N,1,1 from the front panel. The 2015has a female RS232 connector and needs a M/M serial cable (crossover 2<>3, 3<>2, 5<>5). Set to no flow control for now. It also has the option of XON/XOFF flow control which might come in handy.

HP 33120A

Set RS232 comms to 9600,N,1 from the front panel. This unit requires 2 stop bits. It also requires pin 6 (DSR) to be held high when hardware flow control is not used. The unit has a male RS232 connector and needs a M/F null modem cable (2<>2, 3<>3, 5<>5, 6<>6). On the USR-TCP232-2 module I soldered a jumper lead from the +5V power pin to pin 6. Does the job.


HP 34401A

Same as HP 33120A above.