National Instruments offers a wide assortment of solutions that meet the requirements outlined above. To further protect your system from radiated emissions, choose shielded, ruggedly constructed GPIB cables and connector covers that can satisfy requirements for basic and high-performance applications.
Double-Shielded GPIB Cables
The National Instruments X2, X4, and X5 cables are double-shielded for superior noise immunity when compared to standard single-shielded GPIB cables. They have shielded plug/receptacles and an overlapping connector shell seam for superior shielding and grounding. The connector shell is constructed with corrosion resistant, nickel-plated, cast aluminum for ruggedness and superior noise immunity. The combination of the characteristics delivers a minimum of 90 percent coverage and very low capacitance characteristics, going beyond the suggested shield requirements of the IEEE 488 standard.
Looking at figure 1, it can be seen that the double-shielded cables contain three distinct shielding elements. It is less susceptible to noise because it includes an outer copper braid and two inner aluminum/Mylar shields for a total of three shields. This following benefits result:
- Protecting signal lines from external noise
- Cutting radiated emissions from the cable itself
- Minimizing the effects of cross-talk between signal lines, thanks to the inner shields Table 1 shows the double-shielded cable specifications.
Figure 1. Double-Shielded Cable Assembly Diagram
Table 1. Double Shielded Cable Specifications
||4 twisted-pair conductors 26 awg (7/34),
16 twisted-pair conductors 26 awg (7/34),
2 drain wires 24 awg
||Braided shield 36 awg tinned copper,
2 aluminum/Mylar inner shields (90% minimum coverage)
||< [0.25 + 0.153 (L)] W/conductor; L = length in meters
||< 140 pF/m at 25 °C
To complete your system, National Instruments also offers male and female connector covers to prevent dust or other contaminants from corroding or damaging the exposed GPIB cable contacts. The covers also shield the cable contacts from radiated emissions from surrounding equipment.