Emerson Rosemount 644h Instrukcja Obsługi Pobierz pdf (Strona 22)

2-12

Rosemount Inc

SENSOR CONNECTIONS

RTD or Ohm Inputs

The transmitters will accept a variety of RTD configurations, including 2-wire, 3-

wire, 4-wire, and compensation loop designs. If the transmitter is mounted

remotely from a 3-wire or 4-wire RTD, it will operate within specifications, without

recalibration, for lead wire resistances of up to 10 ohms per lead (equivalent to

1,000 feet of 20 AWG wire). In this case, the leads between the RTD and

transmitter should be shielded. If using only two leads, both RTD leads are in

series with the sensor element, so significant errors can occur if the lead lengths

exceed three feet of 20 AWG wire (approximately 0.05 °C/ft).

Thermocouple or Millivolt Inputs

The thermocouple can be connected directly to the transmitter for process

mounting applications. Use appropriate thermocouple extension wire if mounting

the transmitter remotely from the sensor. Make connections for millivolt inputs

with copper wire. Use shielding for long runs of wire.

Figure 2-12. Sensor Wiring Diagrams

Model 644 Sensor Connections Diagram

* Rosemount Inc. provides 4-wire sensors for all single element RTDs. You can use these RTDs in 3-wire

configurations by leaving the unneeded leads disconnected and insulated with electrical tape.

**Thetransmittersmustbeconfiguredfora3-wireRTDinordertorecognizeanRTDwitha

compensation loop.

12341234 12 34 12

41234

644-0000B01A

2-wire

RTD

and 

3-wire

RTD

and 

4-wire

RTD

and 

T/C

and mV

RTD

with

Comp.

Loop

1 2 ... 17 18 19 20 21 22 23 24 25 26 27 ... 67 68

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Emerson Rosemount 644h Instrukcja Obsługi Strona 22