Siemens Pacemaker UM344-2 Bedienungsanleitung PDF herunterladen (Seite 48)

INSTALLATION UM344-2

September 1995

B. RTD/Ohm Sensor-to-Transmitter Extension Cable

The Transmitter will compensate for the effect of lead wire resistance for 3 and 4-wire RTD's and for

an Ohm (potentiometer) sensor when a 3-wire input connection is used. Input connections may be

made with copper wire.

1) Cable Recommendation for RTD: Multi-conductor high temperature cable, overall braid shield

with three copper TFE insulated conductors and TFE wrapped jacket. Wire size

should be 24 to 16 (AWG).

2) Cable Recommendation for Ohm: Multi-conductor standard temperature instrumentation grade

cable, overall braid shield, PVC insulated three copper conductors with PVC jacket. Wire size

should be 24 to 16 (AWG).

C. Millivolt Sensor-to-Transmitter Extension Cable

Cable Recommendation: Multi-conductor standard temperature instrumentation grade cable, overall

braid shield, PVC insulated twisted pair copper conductors with PVC jacket. Wire size should be 24

to 16 (AWG).

4.3.10 2-Wire RTD Accuracy Limitation

The use of a 2-wire RTD requires a careful analysis of the effects of extension lead wire resistance that

can cause an error in temperature measurement.

A 2-wire RTD may be used when the resistance of the run of lead wire may be considered as an additive

"constant temperature error" and the changes in lead resistance due to ambient temperature changes may

be ignored.

The RTD sensor element is approximately one inch in length. The platinum wire at each end of the RTD

is terminated in insulated copper lead wire. The lead wire extends beyond the sensor probe's protective

metal sheath to a distance specified by the user. The lead wires are terminated in the Transmitter's

terminal compartment when the probe assembly is mounted to the Transmitter. On a remote mounted

Transmitter, the lead wires are terminated in the probe's connection head and extended by a second set of

wires to the Transmitter.

The extension lead wire resistance is the sum of the resistances of both copper wires connecting the RTD

element to the Transmitter.

Extension lead wire resistances will add to the resistance of the RTD causing a permanent somewhat

higher temperature reading than actually exists at the RTD location. For example, if a 1 degree offset

error is acceptable, then the maximum #24 AWG extension lead wire length permissible would be

calculated for a 100 Ohm RTD (DIN Curve) as follows:

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Siemens Pacemaker UM344-2 Bedienungsanleitung Seite 48