Page 894 - Basic Electrical Engineering

temperature difference of 750°C. The resistance of the measuring instrument,
R is 100 Ω and gives a full-scale deflection for a current of 0.1 mA. The
m
resistance of junctions and connecting wires is 10 Ω, Calculate the value of a
series resistance that should be connected so that a temperature of 750°C will

give a full–scale deflection of the instrument. If the junction resistance is
increased by 2 Ω due to temperature rise, what would be the measurement
error? The cold junction is maintained at 0°C.

Figure 12.13

Solution:

Current, i for full-scale deflection A=0.1×10 –3

If resistance of the connecting wire junctions rise by 2 Ω, the current flowing
will be

When current flowing is 0.1 mA, the temperature read is 750°C.