Problem 2: A thermocouple giving a 10 mV d. c. output voltage is connected to a high impedance digital voltmeter some distance away. A difference in potential exists between ground (earth) at the thermocouple and ground (earth) at the voltmeter. Using the equivalent circuit given below: (a) Calculate the rms values of the series mode and common mode interference voltages at the voltmeter input. (b) If the digital voltmeter has a common mode rejection ratio of 100 dB, find the minimum and maximum possible measured voltages. Cable R ww 100 Ω Digital Thermocouple 10 ΜΩ voltmeter 10 mV d.c. (d.v.m.) ww 100 Ω S 1000 pF Leakage resistance leakage 10 Ω capacitance U www Thermocouple earth ww 10 Ω T 100 V r.m.s. Voltmeter 50 Hz earth