Detector Wiring Schematic; Maximum Cable Length Calculation - Honeywell 3000 MkIII Series Technical Manual

SERIES 3000 MKIII TECHNICAL MANUAL

6.1 Detector wiring schematic

Caution: All electrical connections should be made in accordance with any relevant local
or national legislation, standards or codes of practice.
Diagram 7: Single barrier schematic
Diagram 8: Dual barrier schematic

6.2 Maximum cable length calculation

The limiting factors in calculating maximum cable lengths when using barriers and isolators are the
total capacitance and inductance. Barriers and isolators have a fixed amount of capacitance and
inductance that can be connected to their outputs. The cable between the field device and barrier/
isolator will have a value for capacitance and inductance per metre or kilometre that will be available
from the manufacturer or supplier.
To calculate the maximum cable lengths, calculate the total capacitance and inductance for the
length of cable, add any capacitance or inductance due to the field device (Series 3000 MkIII
capacitance and inductance = 0). The resulting totals should not be greater than the value shown for
the barrier or isolator.
Example using MTL7787+ dual channel zener barrier:
Capacitance permitted by the barrier = Co
Inductance permitted by the barrier = Lo
Internal capacitance of the field device = Ci
Detector Supply V
• 10 Vdc(+/-10%) < Vd < 30 Vdc (max)
V
d
V
d
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d