Terminology » Measurements » PXI vs. LXI vs. VXI vs. MXI: Interface Comparison

PXI vs. LXI vs. VXI vs. MXI: Interface Comparison

test measurement pxi lxi vxi mxi

This article explores the distinctions between PXI, LXI, VXI, and MXI interfaces, all crucial in the world of test and measurement. These interfaces have evolved to address interoperability, synchronization, and data transfer needs between instruments. Choosing between PXI and LXI, for instance, depends heavily on the specific application and performance requirements.

PXI Interface

Here’s a detailed look at the PXI interface:

  • Full Form: PCI eXtensions for Instrumentation
  • Based on PCI bus architecture.
  • Employs a central processing model similar to a PC.
  • Size is module-dependent.
  • Modules may have interconnection overheads.
  • Requires additional software.
  • Implementation can be cumbersome and potentially less cost-effective.
  • Utilizes 132 Mbytes/sec bandwidth of PCI.
  • Transfer width: 8/16/32/64 bits
  • Throughput: Up to 12 Gbps
  • EMI shields are necessary, depending on module size.
  • Supports modularity.

LXI Interface

The LXI interface is designed for communication between Ethernet-based instruments. It leverages the Ethernet standard, web interfaces, and the IEEE-1588 standard.

The initial version, LXI 1.0, was introduced in 2005, with subsequent improvements leading to versions 1.1, 1.2, 1.3, and 1.4. Power supplies are also designed according to LXI specifications. LXI instruments can support up to 100Mbps.

  • Full Form: LAN eXtensions for Instrumentation
  • It is a distributed system. Communication between instruments is message-based.
  • Offers size flexibility, tailored to vendor requirements for optimal performance.

VXI Interface

VXI is designed to provide:

  • A high-density platform through shared resources.
  • Precise timing coordination between various instruments.

Here are the details:

  • Full Form: VME eXtensions for Instrumentation, based on IEEE-STD-1155
  • Introduction year: 1987
  • Based on VMEbus architecture.
  • Utilizes 40 Mbytes/sec bandwidth of standard VME.
  • Transfer width: 8/16/32 bits
  • Throughput: Up to 160 Mbytes/sec
  • Requires VXI plug and play.
  • Supports modularity.
  • EMI shielding is defined.

PXI vs. VXI: Key Differences

Here’s a comparison table highlighting the differences between PXI and VXI:

SpecificationsPXIVXI
Local Bus13 lines12 lines
Clock10 MHz (TTL Based)10 MHz (ECL) and 100 MHz (D-Size)
Star Bus1 per slotD-size only
Triggers8 TTL8 TTL, 2 ECL, 4 additional ECL (D-size)

MXI Interface

National Instruments (NI) designed and developed the MXI bus interface in 1989. Similar to VXI, it is derived from VMEbus and was later enhanced as the MXI-2 standard in 1995. MXI allows a computer to directly access devices next to VXI or within a 20-meter range.

  • Full Form: Multisystem eXtension Interface
  • Transfer width: 8/16/32 bits
  • Up to 8 MXI devices can be daisy-chained on a single MXI cable (supporting a length of 20 meters).
  • It is an open standard.