Arbiter Systems 1200B, Operation Manual

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128 Options List
B.8.4 Output Load and Loop Example: Unmodulated IRIG-B
When designing circuits for connection to the output bus, several factors must be considered.
1. Loop Resistance
2. Type and quantity of loads connected
3. Maximum loop distance desired
Table B.3 provides a matrix of these factors using the Schweitzer relay(s) as the output load(s). The loop
distance figures were obtained using the following types of Belden Wire (cross-referenced to corresponding
part number):
AWG20 AWG18 AWG16 AWG14 AWG12
Shielded 8762 8760 8719 8720 8718
Non-Shielded 8205 8461 8471 8473 8477
Total Loop Output Load and Voltage Drop – SEL Relays(1) Loop Length (ft.)
Resistance at 0.25 V drop at 0.5 V drop
I(mA) #SEL-2xx(2) I(mA) #SEL-3xx AWG20 AWG18 AWG16 AWG14 AWG12
10 Ω 25 2 50 5 500 800 1200 2000 3000
5 Ω 50 5 100 10 250 400 600 1000 1500
2.5 Ω 100 10 200 20 125 200 300 500 750
1 Ω 250 25 500(3) 50 50 80 120 200 300
Table B.3: Example, Output Load and Loop Distance Matrix
1. Output Load and Voltage Drop, # SEL-3xx is the number of relays connected as output load.
2. For SEL-2xx, using pairs of relays with inputs of each pair in series, the maximum number of relays
is two times that for SEL-3xx.
3. Using 2 drivers in parallel. Parallel connection may be made using AWG22 wire.