PXI tutorial includes:
What is PXI?PXI standardPXI chassisPXI bus and backplanePXI controllerPXI cards & modulesPXI softwarePXI ExpressPXImc MultiComputingSet-up & build PXI system

The PXI chassis provides the means by which the whole PXI test system is able to be held together. It provides the services which the individual cards require for the operation. It also provides everything from the mechanical card holders to the power supply and the air cooling required in such a densely packed volume.

The chassis is standardised so that PXI cards and instruments will not only be able to mechanically fit, but electrically operate to their potential within the chassis.

In order to be able to operate correctly, both cards or test instruments and the PXI chassis must conform to the standard. There are a number of salient features within the specification that enable the cards and the chassis to operate together.

PXI chassis environmental requirements

The PXI specifications states that any chassis that are manufactured should be well suited to harsh environments. Although they are not expected to meet the same requirements as military grade equipment, they should nevertheless be able to operate within many industrial environments. For example it may be necessary to operate a PXI chassis in a factory environment for data acquisition where temperatures may vary beyond those seen in a laboratory or where there is some degree of dirty. Certain levels of vibration may also be seen.

Pxi Chassis Hybrid Slots

This symbol signifies which of the PXI(e) slots the card may be plugged into. Note that some slots can have more than one use (like the last entry of the above table). For example, the a white circle inside a white diamond means the slot can be used as a Star Trigger Slot or a PXI Peripheral Slot. PXI trigger bus; PXI star trigger bus; Slot to slot local bus; In addition to this the specification defines a slot for the PXI system controller. PXI bus system slot. The position of what is termed a PXI system slot is defined. The location of this is on the left end of the PCI bus segment in a basic PXI system. PXI peripheral slots will accept PXI cards of the standard connector types- those that work in current non-express PXI chassis. PXI Express Hybrid slots, due to the hybrid or combination of backplane connectors, accept PXI Express cards, 32-bit CompactPCI cards, and Hybrid Compatible PXI cards (also known as PXI Express-ready or PXIe-ready). PXI Express slots ONLY accept PXI Express modules, of which only a relatively few types are available. Hybrid slots accept EITHER PXI Express or PXI modules, they have both sets of connectors but the second PXI connector is shortened to allow the fitting of the PXIe connector.

To meet these requirements the PXI chassis is based around the Eurocard packaging system used by compactPCI. As part of the system, high performance IEC connectors are used to ensure reliability over long periods of time.

To ensure that the chassis and its associated modules can operate over a sufficiently wide temperature range, the PXI specification includes specific cooling and environmental requirements. These ensure it is able to operate within a variety of industrial environments.

PXI chassis connector system

The connector system used is crucial to its operation. Connectors can be a considerable source of problems, especially when systems are used within non-laboratory environments. Intermittent contacts caused from poor connectors can be particularly time-consuming to fault find. Accordingly a high reliability connector solution was chosen.

Also to maintain compatibility, PXI uses the same pin-in-socket connector system that is found in the CompactPCI racks and systems.

The connectors used in the PXI chassis are defined by the International Electrotechnical Commission, IEC-1076 and offer a high level of performance under all conditions. The connectors pins are on a 2 mm pitch and are also impedance matched so that they provide a high level of performance within the chassis and are able to provide PXI systems more slots on a single bus segment than traditional desktop PCs systems.

Basic PXI chassis parameters

The chassis system is based around the Eurocard packaging system. This provides a number of advantages including a system that is already established. Furthermore the connectors that are used are the IEC-1076 style. The pins are on a 2 mm pitch giving a very dense connection system. In addition to this they are impedance matched to provide the required performance at high frequencies.

The PXI system supports the two sizes, namely 3U and 6U with the details outlined in the table below:

The 3U standard has two interface connectors. One carries the signals required for the 32-bit PCI local bus and the other carries the signals for 64-bit PCI transfers and the signals for implementing various electrical features of the system. The 6U form factor defines modules that may carry up to two additional connectors for future expansion of the PXI specification. The larger card size also allows for a additional circuitry that may be required for some instruments.

In general the 3U PXI chassis and modules are more widely used. However the 3U modules can be fitted into a 6U chassis using a simple adaptor.

PXI chassis widths

PXI chassis come in a number of different sizes and the correct chassis size or type can be chosen for a given application. There is no need to buy a large chassis at extra cost if only a small number of cards are to be used.

Generally there are two sizes of chasses - a full 19 inch rack compatible size and a half rack width.

The full rack width chassis typically has 18 slots, whilst the half sized chassis has 8 slots.

PXI chassis slots functions

Each PXI chassis has a number of slots. As mentioned above the chassis have either eight or eighteen slots. Not all the slots can be used for all cards. There are some positions reserved for particular applications.

• Slot 1: Slot 1 in the PXI chassis is reserved for the controller - this is the only position in which the controller will operate. Normally this is 4 units wide to allow for all the space required for embedded controllers, although some controllers could be smaller. Cards that link out to computers to provide the control are often only one module width and therefore in these circumstances blanking plates may be required to cover the empty space.
• Peripheral slots: These are slots that can be used for the test instruments, etc. There may be some restrictions on the types of module that can be used in terms of PXI, PXIe, etc, but these are indicated by the glyphs on the chassis as described below.
• Timing slot: On larger chassis a timing slot may be indicated. This can be used for normal peripheral modules, but it is also the one to be used if any timing or synchronising modules are to be used. This slot is on the bridge between the two sides of the chassis and it provides the shortest delay between all the modules in the rack.

As a further note, if large amounts of peer to peer streaming is required, then it is best to place the two modules that will be streaming the data on the same side of the backplane bridge, i.e. on the same side of the timing slot.

PXI chassis glyphs

In order to identify the different types of modules that can be accommodated within a PXI chassis, small identification glyphs are used with each slot to highlight what it can accommodate.

The numbers in the glyphs normally refer to the slot number, but in this instance the explanations are linked to the glyph numbers:

• 1 PXI Express system slot
• 2 PXI-1 peripheral slot, i.e. the basic PXI before PXIe was introduced.
• 3 PXI Express hybrid slot - i.e. it will accommodate both PXIe, and the basic PXI
• 4 PXI Express only peripheral slot
• 5 PXI Express system timing slot

It can be seen how the PXI chassis identification glyphs are shown and how they indicate the capabilities of each slot.

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PXI tutorial includes:
What is PXI?PXI standardPXI chassisPXI bus and backplanePXI controllerPXI cards & modulesPXI softwarePXI ExpressPXImc MultiComputingSet-up & build PXI system

PXI, PCI eXtensions for Instrumentation, has emerged as a major force in the test equipment and instrumentation industry.

PXI provides a rugged PC based platform for use in automated test, data acquisition and many other applications.

It successfully combines rugged mechanical elements with a high electrical performance specification and a low cost. Using standard PC technology, this makes PXI an ideal platform for a host of applications

Pxi Slots Free

What is PXI? - the basics

PXI is based on the popular PC based bus system, CompactPCI, used for embedded development and computer based platforms As such PXI is able provide the benefits of the PCI architecture: high level of performance, industry acceptance, wide availability of off the shelf units, etc. PXI adds a rugged Compact PCI mechanical form-factor, an there is an industry consortium that defines hardware, electrical, software, power and cooling requirements, enabling interconnectivity between items from different manufacturers.

In addition to this, the system adds a number of other capabilities required for test, measurement, data acquisition and control applications. These include aspects including: integrated timing and synchronization that is used to route synchronization clocks, and triggers internally.

A further advantage of PXI is that having been adopted by the industry it will remain in use for many years to come, thereby enabling any investment to be protected. These advantages make PXI an ideal standard for use as test equipment and for data acquisition applications. Read more about the PXI standard & specifications.

PXI Hardware

The PXI hardware is platform on which the overall PXI standard is based. It forms the platform for running the software and for the individual instruments. It forms a particularly flexible scheme allowing a very wide variety of instruments to operate within a chassis environment.

There are three basic elements to a PXI system:

• PXI Chassis: The chassis is the most visible element of the system. The PXI chassis literally provides the framework for the system and it normally can range in size from four slots up to eighteen.
  The PXI chassis contains a high performance backplane enabling the cards in the system to be able to communicate rapidly with one another and in addition to this timing and triggering lines are also included.
  To put this in context, a typical 3U PXI module measures approximately 100 x 160 mm (4x6 inches), and a typical 8-slot chassis is 4U high and half rack width, full width chassis contain up to 18 PXI slots.
• System controller: A system controller card is located in left hand slot in the rack, or alternatively control can be undertaken by a remote PC. The use of a standard PC provides a particularly cost effective, but powerful option for many users.
  In this way the convenience of a standard PC can be combined with the power that they are able to offer these days. However the use of a controller module is also convenient in many applications and these leverage on the wide variety of PC cards and modules that are available.
  Read more about . . . . PXI controller.
• Modules or instruments that slot into the chassis: There is a very wide variety of modules that are available. They include test instruments for taking a wide variety of measurements, e.g. voltage, current, frequency as well as signal and waveform generators. However modules are also available to perform other functions including boundary scan testing, digital or analogue input and output, image acquisition, power supplies, switching and much more.
  By choosing modules to meet the requirements of the overall PXI system it is possible to build up a flexible test or automation system that can be easily tailored to meet virtually any requirement.

PXI software

Many PXI instrument modules or cards are register based items. They use software drivers that can be hosted on the central controller PC and these configure in the way that the PXI modules are set up for the particular application in question. By adopting this technique it enables them to provide considerably more flexibility as the controller PC is able access the instrument directly and this simplifies the embedded software in the modules while enabling a high level of flexibility to be obtained. The open architecture allows hardware to be reconfigured to provide new facilities and features that are difficult to emulate in comparable bench instruments.

In addition to this a number of vendors offer software to run the automated tests and data acquisition applications. These proprietary products provide a high degree of sophistication, while being designed to operate with PXI. In addition to this they can be configured to meet the requirements of an individual application, be it for automated test, or data acquisition.

Major features of PXI technology

The PXI system boasts many features that make it a flexible platform for many applications. The highlight features of the PXI standard are detailed in the table below:

The PXI standard is a particularly successful open architecture test equipment standard that is widely used for a variety of applications. The system can be used to provide automated test, as well as fulfilling a variety of other data acquisition requirements. This makes PXI an ideal standard to be considered where automated test and data-logging are needed.

More Test Topics:
Data network analyzerDigital MultimeterFrequency counterOscilloscopeSignal generatorsSpectrum analyzerLCR meterDip meter, GDOLogic analyzerRF power meterRF signal generatorLogic probePAT testing & testersTime domain reflectometerVector network analyzerPXIGPIB Boundary scan / JTAG
Return to Test menu . . .