Solartron Mobrey 3595 4C, User Manual

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Preparing and Installing The 3595 4C Interface 3595 4C User Manual Part One
2-8
35952350 (CH02/AA)
2.5.1
S-Net cables
3595 Series IMP devices are linked to the 3595 4C Interface card by S-Net , a serial communications
network. The S-Net cable consists of a twisted pair of multi-stranded wires with a screen around them, and
has a nominal characteristic impedance of 100
Ω
. Non-screened cables may be used, but S-Net signals
may be subject to interference in electrically ‘hostile’ environments. In most applications, signals and IMP
power are delivered via the S-Net cable that is connected to a D-type connector on the 4C Interface card.
Table 2.2: Cables recommended for S-Net
Cable Gauge Brand Names Solartron Mobrey P/N
12 AWG Brand-Rex T12459 TBA
16 AWG Brand-Rex T12460, Alpha 9820, Belden 9860 TBA
18 AWG Brand-Rex CD8920251, Belden 9250 TBA
20 AWG Brand-Rex BC 57207, Alpha 9818
Belden 9207, Belden 0915 (direct burial) TBA
24 AWG Brand-Rex B156641, Alpha 2400, Belden 8641 TBA
Note:
Approximately 10 metres of 24 AWG Belden 8641 cable are provided with each module. This is sufficient
for small data acquisition systems or for testing purposes.
The connections are: S-Net +ve = black (or red) and S-Net –ve = white.
2.5.2
Cable selection
Cable selection depends on two cable characteristics:
1.
The a.c. attenuation of the cable. This affects the digital communications that are running back and
forth along the cable, between the IMP devices and the 4C Interface card. There are two specific
points to consider:
a. The high a.c. attenuation of the 24 AWG cable means that S-Net using this cable can not be longer
than 660 metres.
b. The low a.c. attenuation of the 14 and 18 AWG cables means that S-Net using these cables can
extend up 1.5km. The large diameter of these cables necessitates special consideration when
making connections to the IMP. For details, see the “3595 Series IMP Installation Guide” or
consult Solartron Mobrey.
2.
The d.c. resistance of the cable. This, and the voltage of the power supply, determines the maximum
number of IMP devices that can be powered via the cable. Generally, if any IMP devices on the
network are powered from the 4C Interface card via the S-Net cable, it is important that a cable of
adequate gauge is used. The optimum cable size depends on the number of IMP devices to be
powered via the S-Net cable, the cable length and the power supply voltage. Guidance on choosing
the cable, either for power provided internally from the 4C Interface card or from an external supply via
the 4C Interface card, is given in Sections 2.5.3 and 2.5.4.