- #1
PaxFinnica96
- 14
- 0
- Homework Statement
- a. The resistance thermometer bridge circuit shown in FIGURE 1 has a designed maximum temperature of 200°C, ignoring the effects of connecting wire resistance. If the connecting loop is 250 m determine the smallest gauge (swg) of copper wire which must be used if the indicated maximum temperature is to be less than 202°C.
The temperature coefficient of resistance of the thermometer is 0.0042 °C–1 and the resistance of the thermometer is 112 Ω at 20°C. Assume the connecting leads are at 20°C.
b. Using the gauge of copper wire calculated in part (a), calculate the maximum indicated temperature using a 3-wire system (as shown in FIGURE 2) over a distance of 125 m.
- Relevant Equations
- Rt = R0(1 + at)
R1RT = R2RS
R = pL/A = Resistance = (Resistivity) x Length of wire / cross-sectional area
A = (pi x d2) / 4
d = squareroot(4A /pi)
Hi All,
Really struggling to get my head around what I'm doing wrong - every time my answer of wire diameter comes out too small for what's included in the table of SWG. I must be doing something wrong somewhere - my attempt is below.
Any help is very much appreciated.