Fisher 244EH, 244ER manual Thermocouple or Millivolt Inputs

• Pt100 2-wire RTD:

Lead Wire Resistance

Basic Error = ----------------------------------------------------------

(αPt × Ro)

(αCu ) × ( ΔTamb) × (Lead Wire Resistance) Error due to amb. temp. variation = ----------------------------------------------------------------------------------------------------------------

(αPt) × (Ro)

Lead wire resistance seen by the transmitter = 150 m × 2 wires × 0.025 Ω/m = 7.5 Ω

Basic error =	7	.5 Ω	= 19.5 °C
	(---0.00385------------------------Ω-------/---	Ω-------°---C-----)----×----(---100------------Ω-----)

Error due to amb. temp. var. of ± 25 °C

(0.0039 Ω / Ω °C) × (25 °C) × (7.5 Ω) ± °

=-------------------------------------------------------------------------------------------------------= 1.9 C

(0.00385 Ω / Ω °C) × (100 Ω)

Thermocouple or Millivolt Inputs

For integral mounting applications, the thermocouple can be connected directly to the transmitter. If mounting the transmitter remotely from the sensor, use appropriate thermocouple extension wire. Make connections for millivolt inputs with copper wire. Use shielding for long runs of wire.

Figure 2-12. Sensor Wiring Diagrams

	Model 244E Sensor Connections
1 2 3 4	1 2	3	4	1 2	3 4	1 2 3 4	1 2 3 4	0000B01A-
2-wire			*		**	4-wire	T/C
	3-wire			RTD with				644
RTD	RTD			Comp.		RTD	and mV
and V	and V			Loop		and V

*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.

**The transmitters must be configured for a 3-wire RTD in order to recognize an RTD with a compensation loop.

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