West-control-solutions MRC 7000 Controller Manual Uživatelský manuál stáhnout pdf (Strana 13)

RTD LEAD RESISTANCE

RTD lead length can affect instrument accuracy. Size (gauge) and length of the wire used

affects lead length resistance.

To determine the temperature error resulting from the lead length resistance, use the following

equation:

Terr = TLe * L where; TLe = value from Table 3 if 3 wire or Table 4 is 2 wire.

L = length of leadwire in thousands of feet.

TABLE 3 3 Wire RTD

AWG No. Error °C Error °F

10 +/-0.04 +/-0.07

12 +/-0.07 +/-0.11

14 +/-0.10 +/-0.18

16 +/-0.16 +/-0.29

18 +/-0.26 +/-0.46

20 +/-0.41 +/-0.73

24 +/-0.65 +/-1.17

TABLE 4 2 Wire RTD

AWG No. Error °C Error °F

10 +/-5.32 +/-9.31

12 +/-9.31 +/-14.6

14 +/-13.3 +/-23.9

16 +/-21.3 +/-38.6

18 +/-34.6 +/-61.2

20 +/-54.5 +/-97.1

24 +/-86.5 +/-155.6

Example

An application uses 2000 feet of 18 AWG copper lead wire for a 3-wire RTD sensor. What is

the worst-case error due to this leadwire length?

Terr = TLe * L

TLE = +/- .46 (°F/1000 ft) from Table 1

Terr = +/- .46 (°F/1000 ft) * 2000 ft

Terr = +/- 0.92 °F

1 2 ... 8 9 10 11 12 13 14 15 16 17 18 ... 73 74

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West-control-solutions MRC 7000 Controller Manual Uživatelský manuál Strana 13