More about the 35954C PCI Interface card

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SNet to Host Computer interface

The Isolated Measurement Pod (IMP) system – originally developed in the early 1980s by Solartron Instruments – has a long pedigree and an enviable reputation for accuracy and reliability with many thousands of units installed throughout the world.

For existing IMP/IMC users who wish to or who need to update their host computer systems, two interface options are available, consisting of the re-engineered 35954C PCI bus adaptor card and the 35954U SNet-to-USB interface.

These two provide a choice for both existing and new IMP system users who wish to take advantage of modern processor technology, whilst still retaining the use of the excellent IMP / SNet system.

These interfaces provide:-

  • Control commands for measurement set-up
  • Measurement initiation
  • Measured data retrieval
  • Synchronised time stamping across the network
  • DC Power to all connected IMPs
  • Full timing control and error checking are performed on the data.

35954C Features and Specifications

The card occupies one slot in the PC, and contains its own data buffering.

Data is exchanged with the PC via the 64K dual-port RAM which is divided into 512byte pages, each page dealing with a particular aspect of IMP operation.

Several cards, each driving a separate S-Net, may be present in one PC if required.  Each S-net supports up to 50 IMPs.

The interface can power up to 5 IMPs via the PC’s internal supply; for larger systems an external power supply must be connected.  This power supply can be situated by the PC, using the S-net to supply each IMP, or may be local to the IMPs, supplying power directly to each IMP.

35954C Connections

  • 124-way edge connector for PCI expansion slot
  • 9-way D-type female connector for S-Net
  • 9-way D-type male connector for external power

Physical (half-length PC I/O card



,,,127mm (6.8″),107mm (4.2″),20mm (0.8″),0.2Kg (0.44lbs),,,


General items

S-Net communication capability

  1. Maximum number of IMPs: 50
  2. Maximum length of cable: 1500 m

Power Supply requirements

  • Power from PC Supply
  1. PC loading : 5V, 2.5W maximum
  2. 12v: 1.2W for each IMP
  3. Maximum number of IMPs: 5
  • External Power Supply
  1. Output voltage: 12V to 50V
  2. Supply ripple: <1000mV rms
  3. Power Drain: 1.2W per IMP
  4. Maximum number of IMPs: 50


  • Temperature


0°C to 55°C (32°F to 131°F) @ 50%RH

0°C to 45°C (32°F to 113°F) @ 95%RH


-40°C to 70°C (-40°F to 158°F)

IMP Genealogy

Following a series of changes of ownership during the early 2000s, the then owners elected to cease manufacture of the IMP system. It was then that Zeefax was able to acquire the intellectual property rights (IPR) for the whole range of products, and since 2012 have embarked on a program of re-manufacture.

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