EETC Instrumentation 2

Question 1

What is the standard live zero signal range used in industrial 4-20mA current loops?

Accepted Answer

4-20mA

Answer

The 4-20mA standard uses 4mA as the live zero, allowing detection of broken wires (which read 0mA, below the live zero).

Question 2

A thermocouple produces a voltage based on which physical principle?

Accepted Answer

Seebeck effect

Answer

The Seebeck effect describes the generation of an EMF at the junction of two dissimilar metals exposed to a temperature difference.

Question 3

An RTD (Resistance Temperature Detector) measures temperature by:

Accepted Answer

Changing resistance with temperature

Answer

RTDs exploit the predictable, repeatable increase in electrical resistance of metals (typically platinum) as temperature rises.

Question 4

Which instrument measures the true RMS value of a non-sinusoidal AC waveform most accurately?

Accepted Answer

True RMS voltmeter

Answer

A true RMS meter computes the square root of the mean of the squared instantaneous values, correctly handling distorted waveforms.

Question 5

In a differential pressure (DP) flow transmitter, flow rate is proportional to:

Accepted Answer

The square root of differential pressure

Answer

Bernoulli's equation relates flow velocity to the square root of pressure difference, so volumetric flow = K × √ΔP.

(EETC) Electrical Technician Certification Practice Test