Emerson Micro Motion MVD Direct Connect, Руководство по установке

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12 Direct Connect Meters
Installation
3.1.2 MVD Direct Connect installations with the
MVD Direct Connect I.S. barrier
In MVD Direct Connect installations with the I.S. barrier, power is supplied to the barrier.
The barrier supplies power to the core processor, and the core processor supplies power to
the sensor. The power supply must meet the following requirements:
• The power supply can be either floating or grounded.
• The voltage requirement for a single barrier is 24 VDC ±20%. The maximum power
consumption of a single barrier plus core processor is approximately 3.5 W.
• The power supply cable must comply with the size and length requirements listed in
Table 3-3 . A minimum DC input of 19.2 V is required at the barrier terminals. At
startup, the power source must provide a minimum of 0.2 A of short-term current per
core processor. The maximum steady state current is 0.15 A. For assistance in sizing
the power supply cable, refer to
Table 3-1 and use the equation below:
Example
The core processor is mounted 350 feet from a DC power supply. If you want to use 18 AWG cable,
calculate the required voltage at the DC power supply as follows:
Table 3-1 Typical power cable resistances at 68
°
F (20
°
C)
Gauge Resistance
14 AWG 0.0050  /foot
16 AWG 0.0080

/foot
18 AWG 0.0128

/foot
20 AWG 0.0204  /foot
22 AWG 0.0328

/foot
2,5 mm
2
0,0136

/meter
1,5 mm
2
0,0228

/meter
1 mm
2
0,0340

/meter
0,75 mm
2
0,0460

/meter
0,5 mm
2
0,0680

/meter
Note
These values include the resistance of both high and low conductors in a cable.
MinimumSupplyVoltage 15V 0.0128 ohms/ft 350 ft

0.15A
  
+ =
MinimumSupplyVoltage 15V CableResistance CableLength

0.15A
  
+ =
MinimumSupplyVoltage 15.7V
=
MinimumSupplyVoltage 19.2V CableResistance CableLength

0.15A
  
+ =