Addressing instruments with VISA
VISA allows you to communicate with the instrument on different communication buses by changing a
resource string that gets passed in with the viOpen function, in VISA-C, or with the Open method on
the VISA-COM resource manager object.
For detailed information about the format of the resource string, refer to the VISA specification
VPP4.3 at the IVI Foundation website, or refer to the help file provided by the vendor of the VISA
implementation you are using.
The following sections describe the resource strings for some of the communication types that
Keithley supports. Any field that has [] (square brackets) around it is optional and will revert to a
default value.
Addressing instruments through the LAN
VISA supports two different LAN protocols, each of which has a different resource string.
VXI-11 is a protocol that emulates GPIB over the LAN. Series 3700A supports this protocol. The
resource string is:
TCPIP[board]::host address[::LAN device name][::INSTR]
board is the network interface card in the computer. This value is usually skipped and VISA
determines the correct network interface card (if you have more than one) by looking at the IP
address.
host address can be either a valid DNS hostname, mDNS hostname, or the IPv4 IP (only) address
of the instrument.
LAN device name is a method of addressing secondary instruments at the main IP address, similar
to secondary addressing on the GPIB bus. The default is inst0.
A raw socket connection requires more work by the driver or application program to make sure the
correct amount of data has been sent or received correctly. All Keithley instruments support the raw
socket connection.
TCPIP[board]::host address::port::SOCKET
The board and the host address are the same as for the VXI-11 protocol.
port is the port to which to connect on the instrument. For the Series 3700A, the port is 5025.
Addressing instruments using USB
USB[board]::manufacturer ID::model code::serial number[::USB interface
number][::INSTR]
board is not used (0).
manufacturer ID is the USB.org reserved four-digit hexadecimal code for the instrument vendor
company. Keithley Instruments hexadecimal code is 0X5E6.
model code is the model number of the instrument. For example, when addressing a Model 3706A,
use 0X3706.
serial number is the serial number of the instrument.
USB interface number identifies which USBTMC interface on the instrument to address
(usually 0).
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