We have seen some instances where the serial number is reset to 0. You can reset the serial number by the steps below,
1. On the 6270A go to the <Setup>, <Instrument Setup>, <Remote Port>, screen and verify that the <Emulation Mode> is set to "SCPI".
2. Click <USB Setup> and on that screen verify that "Remote IF" is set to "Computer", and "RS232 Emulation" set to "ON".
3. Connect the USB cable to the computer and to the back panel USB connector on the 6270A.
3. The computer should recognize the 6270A as a serial port. If not, see this article 6270A Pressure Controller USB Driver (also 2271A, 8270A/8370A)
4. It is a good idea to verify the connection by sending the following commands *IDN?, the replay should be FLUKE,6270A,1234567,1.XX ( Where 1234567 is the serial number and 1.xx is the main firmware revision)
5. Reset your serial number by sending the following set command
diag:system:name xxxxxx (where "xxxxxx" is the serial number)
It is normal to get an error from this because there is no replay from the controller.
Verify the serial number is correct by sending the following read command
6. If you want to update the firmware, see this article for instructions and firmware version history, 6270A firmware update instructions
7. If you communicate with the controller by a USB COM port go back to the <Setup>, <Instrument Setup>, <Remote Port>, <USB Setup> screen and change the "Remote IF" back to "Terminal" and "RS232 Emulation" back to "ON".
If you need serial communication software, see this article Remote Communication by Serial RS232 using PuTTY telnet client