What statement is true concerning the arrangement and operation of the viscosity transmitter as used for indicating the viscosity of heavy fuel oil?

Correct Answer: Option A — The viscosity transmitter is a differential pressure transmitter receiving both capillary tube inlet and outlet pressures from the viscosity sensor and delivering a single viscosity signal to the viscosity indicator.

Viscosity transmitters measure the pressure drop across a capillary tube through which a constant flow of fuel is maintained. Because the pressure drop is directly proportional to the fluid's viscosity at a constant flow rate, the differential pressure transmitter provides an accurate signal for the viscosity control system.