Emerson Rosemount 644h Instrukcja Obsługi Pobierz pdf (Strona 25)

SECTION

3-1

3 Operation

Safety Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 3-1

Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 3-1

Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 3-2

SAFETY MESSAGES

Instructions and procedures in this section may require special precautions to

ensure the safety of the personnel performing the operations. Information that

raises potential safety issues is indicated by a warning symbol ( ). Please refer to

the appropriate safety messages listed in “Warnings” on page 1-1 before

performing an operation preceded by this symbol.

POWER SUPPLY

The dc power supply should provide power with less than 2 percent ripple. The

power supplied to the transmitter should not drop below the transmitter operating

voltage. Use Figure 3-1 to calculate the maximum resistance load. Compare this

with the total resistance load, which is the sum of the resistance of the signal leads

and the load resistance of any controller, indicator, or related pieces of equipment

in the loop. The resistance of intrinsic safety barriers, if used, must be included in

the maximum resistance load calculation. The supply voltage will need to be

increased if the total resistance exceeds the maximum resistance load.

NOTE

HART communication requires a minimum of 17.75 dc power supply and a loop

resistance of 250 to 1100 ohms. Do not communicate with the transmitter when

power is below 12.0 V dc at transmitter terminals.

Figure 3-1. Load Limits

Maximum Resistance Load = 43.5 x (Supply Voltage – 12.0)

–

1322

1100

1000

750

500

250

12.0 42.4

Load (Ohms)

Supply Voltage (V dc)

Operating

Region

644_08A

4030200

1 2 ... 20 21 22 23 24 25 26 27 28 29 30 ... 67 68

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Emerson Rosemount 644h Instrukcja Obsługi Strona 25