Choosing the Correct Interface for Your Instruments

This topic provides guidelines for selecting the most suitable interface to connect instruments to PCs, considering the available options on both sides of the connection.

First, determine the interfaces that are available to you on each side of the connection (instrument and PC). Not all interfaces are available on all instruments. PCs typically have USB, LAN, and a limited number of serial interfaces available, but require the addition of a card (such as the Keysight 82350 PCI GPIB Card) to support GPIB.

Adaptor products are available to connect a PC to GPIB instruments using either the PC's USB interface (Keysight 82357 USB/GPIB Interface Converter) or its LAN interface (Keysight E5810B LAN/GPIB/USB Gateway). These products provide convenient and powerful ways for you to take advantage of PC-standard I/O with a large range of instruments from many manufacturers.

Supported Interface Types

The interfaces that can be used with Keysight IO Libraries Suite are:

 

LAN Interface

A LAN (TCP/IP) interface is a logical collection of properties that can apply to remote interfaces and instruments. A LAN interface does not directly represent physical devices. Several physical devices may be auto-discovered or manually added on a single LAN interface. In this case, the interface properties apply to all related devices.

The default LAN interface is TCPIP0. Changing properties of this interface (such as timeouts) will apply to all its associated LAN instruments. To maintain two or more groups of instruments with different interface properties, add a new LAN interface, and then add instruments specifying the interface whose properties you wish to apply to that instrument.

Adding new interfaces offers several advantages, including enhanced organization of instruments within the view, the ability to utilize various protocols, and greater control over timeout values.

A local area network (LAN, also known as Ethernet) provides instrument connectivity over distances and allows sharing of instruments among multiple users and multiple PCs. Ethernet LANs are almost universally available; they support data rates of 10 to 1000 megabits/second, and they use inexpensive cables and connectors. Many instruments have LAN interfaces built-in; for those that do not, you can use the KeysightE5810B LAN/GPIB/USB Gateway. LAN is a recommended method to connect instruments together in applications such as new test systems.

You can connect your instruments to a private LAN or to a site LAN.

  • A private LAN is set up specifically for your use in connecting your instruments. Typically, you will be the administrator of the private LAN, and you will control connections, cabling, and addressing. Your PC and all instruments are connected via a networking switch or router that isolates them from your site LAN. You can think of a private LAN as just another type of bus for your test system, like GPIB or USB; the private LAN is used only by your test system. You should use a private LAN if you want total control of your network and instruments, or if it is important that your test system achieve maximum throughput.
  • Your site LAN is the network you use to connect with other PCs, printers, and devices in your work group. Your PC is probably already connected to the site LAN; you use the site LAN to connect to your intranet or to the Internet. If you want to share instruments with other users, or if you need access to instruments across an intranet or the Internet, you can use your site LAN. You may need to work with your IT department to put your instruments on the site LAN.

LAN Interface Properties

Click here to learn about LAN interface settings.

Different Types of LAN Connections

GPIB Interface

The General Purpose Interface Bus (GPIB) is fast and robust method requiring a dedicated PC card and additional configuration. It is ideal for instruments with only GPIB and serial connectors.

A GPIB interface can be any of the following:

Instrument Discovery and Identification

When IO Libraries detect a GPIB interface, you will be able to add a GPIB instrument.

The Discovery Service detects and identifies instruments on GPIB interfaces.
  • On startup, the service sequentially addresses primary and secondary GPIB addresses to find connected instruments.
  • Discovery runs whenever the interface is scanned.
    • Keysight GPIB instruments are addressed only if their state changes.
    • Non-Keysight instruments are addressed every time.
  • The service sends an *IDN? query to newly discovered instruments unless they have an open session.

Manual Options

  • You can choose to turn off:

    • auto-scan and auto-discovery for Keysight GPIB interfaces.
    • auto-discovery for 488.2 GPIB interfaces and remote GPIB interfaces, but those interfaces do not support auto-scan.

  • You can manually add GPIB instruments that have not been auto-discovered. If you manually add a GPIB instrument, you can choose to turn off auto-identification for that instrument.

Automatic Disabling of GPIB Auto-Scan

The GPIB auto-scan feature scans the interface in a way that is designed to avoid putting instruments into remote mode (i.e., disabling front panel control). However, some instruments (for example, some Keysight 34410As and 34980As) do go into remote mode when scanned in this manner. When the Discovery Service detects an affected instrument model, it turns off auto-scan for the affected GPIB interface.

This may occur with various instruments; whether you are affected by this issue may depend on the version of firmware on your instrument. For up-to-date information about compatibility issues and solutions, including a list of affected instruments, visit www.keysight.com/find/iosuitecompatibility.

USB Interface

Instruments connected via USB are auto-discovered. There are no editable parameters on a USB interface.

The Windows Plug&Play Manager keeps track of all USB devices that are attached to the PC, and provides a list of connected devices. When the software notices a new USB device, it considers this device to be newly-discovered.

Serial (RS232) Interface

A serial interface is an RS-232 (ASRL) port on your PC.

The Discovery Service identifies the serial interfaces available, but does not discover serial (RS-232) instruments. You must add them manually. When you add a serial instrument, you can choose whether it will be auto-identified (with *IDN?) or not.

Serial connection is inexpensive and widely available, but is slow compared to other I/O interfaces, and requires particular attention to cabling and configuration. Instruments connected via serial port cannot be automatically detected by I/O software. Connect your instruments via serial port only if these factors are not a concern for you, or if no other option is available. If you select serial connections, see Add a Serial Instrument for information on configuring these connections.

VXI

The Discovery Service communicates with the VXI Resource Manager to obtain a list of VXI devices. It does not communicate directly with the VXI cards.

E8491 IEEE-1394 to VXI controllers

The Keysight E8491B IEEE-1394 PC Link to VXI is a C-size, 1-slot, message-based VXI module. The E8491 provides a direct connection from your PC to a VXI mainframe via the industry standard IEEE-1394 bus (FireWire). The E8491B is a cost-effective choice for test applications and is well suited for data acquisition applications moving large blocks of data.

The E8491 is a high-speed C-size device with Resource Manager and Slot 0 capability. Its logical address is 0, therefore it is always the mainframe's Resource Manager and is typically installed in mainframe Slot 0. The high speed is accomplished, in part, through the use of small signals (200 mV) that are transmitted differentially over the twisted-pair wire set with controlled-impedance characteristics. The differential signal provides high-noise immunity.

VXI systems are specialized for applications requiring high-performance electronic testing.

GPIB-VXI Interfaces

A GPIB-VXI interface consists of a GPIB interface in the PC connected to a VXI command module (either Keysight or National Instruments) in slot 0 of the VXI mainframe. The GPIB-VXI interface allows you to use all of the VISA VXI-specific functions (such as viIn, viOut, viMapAddress, viPeek, and viPoke) even though you are connected through a GPIB interface.

PXI and AXIe Interface

The Discovery Service communicates with the PXI Resource Manager to obtain a list of devices. It does not communicate directly with the PXI cards.

Software Servers

The Discovery Service adds these interfaces for SCPI servers. You do not need to add, edit, or delete these interfaces, but they can be seen in Instrument View. Note: You may need to change the Localhost options in Settings when using software servers.

Remote GPIB Interface

A remote GPIB interface is a device on a LAN that provides connectivity to instruments via GPIB. It is typically either a gateway, such as the Keysight E5810B LAN/GPIB/USB Gateway, or a computer running the Remote IO Server software. (SeeRemote IO Server Options for more information about the Remote IO Server software.)

The Discovery Service discovers instruments on a remote GPIB interface:

  • When you add the interface for the first time.
  • When you reboot the PC running IO Libraries.
  • When you rescan interfaces.

Note: Auto-scan does not operate on remote interfaces. If you turn off auto-discovery on a remote interface, you must manually add instruments to that interface.

Remote Serial Instrument

A remote serial instrument is an instrument connected via serial (RS-232, or COM port) to a server on a LAN. The server is typically a computer running the Remote IO Server software. (See Remote IO Server Options for more information about the Remote IO Server software.)

The Discovery Service does not discover serial (RS-232) instruments. You must add them manually.

Remote USB Interface

A remote USB interface is a device on a LAN that provides connectivity to instruments via USB. It is typically either a gateway, such as the Keysight E5810B LAN/GPIB/USB Gateway, or a computer running the Remote IO Server software. (See Remote IO Server Options for more information about the Remote IO Server software.)