8.4 Connecting Outputs
69
by the user, if required, to ensure that maximum ratings are not exceeded even momentarily. Also,
before using the 300-Volt FET, please check the data sheet of the IRF740S used in this application.
8.4
Connecting Outputs
The Model 1094B comes equipped with two types of output connectors: BNC female and screw
terminals. BNC connectors are compatible with most coaxial cables. Terminal connectors are
compatible with twisted pair cabling, in which the wires are stripped bare, tinned and fixed into
the correct screw terminal positions.
NOTE: If using a shielded, twisted-pair cable (like Belden 8760), DO NOT connect the cable shield
at the clock. Always connect a cable shield at the receiving equipment (IED) grounding point.
8.4.1
Attaching Cables to Screw Terminals
Prepare the twisted pair cable by stripping back at least 1/4 inch of the insulation and any shielding.
DO NOT tin the bare wire with solder. Tighten the screws down on the wire.
Do not ground the
shield to the Arbiter clock
.
8.4.2
How Far Can I Run IRIG-B Cabling?
Some important considerations for transmitting IRIG-B over long distances are: (1) resistive losses
in cabling, (2) electromagnetic interference, (3) propagation delays and (4) installation and main-
tenance costs.
For details on distributing IRIG-B signals over long distances, see application note, AN101, Dis-
tributing Timing Signals in a High-EMI Environment. Download file
appnote101.pdf
at the follow-
ing link:
http://www.arbiter.com/ftp/datasheets/
For important considerations about IRIG-B connections, distribution of signals and accuracy, down-
load the file,
IRIG-B accuracy and connection requirements.pdf
at the following link:
http://www.arbiter.com/ftp/datasheets/
.
8.4.3
Synchronizing Multiple Devices From One Masterclock Output
In many installations, master clock signals (e.g. the 1094B) are “fanned out” to a number of devices.
This method makes more efficient use of the clock synchronizing capability since the clock drivers
are designed to handle multiple loads. The exact number of possible loads must be determined
from the input impedance of each connected IED, which sets the current drawn from the specific
1094B output. In calculation 8.1, the device current (I) is calculated from the output voltage (V)
and the input impedance (Z) of the IED, which is 5 kilohms.
(8.1)
I
=
V /Z
= 5
V olts/
5000
Ohms
= 0
.
001
Amps
(1
mA
)
If you were to connect ten of the same devices to the same output, then the total current drawn
would be 10 x 0.001 A = 0.01 A (10 mA).
