Transmission System Maintenance. Information needs to be transmitted
from the sensing device, which measures the variable, to the instruments that indicate,
record, or total it. The transmission system may be mechanical, hydraulic, pneumatic,
or electrical. Each system consists of two components--the transmitter and the
transmission link. Maintenance procedures for transmission systems are summarized
in Table 28.
Indicator, Register, and Recorder Maintenance. Besides transmission
devices, secondary instruments include indicators or gages (momentary indication of
discrete information), recorders (chart record of information by time), and registers or
totalizers (also termed "integrators"). The latter category expresses the total quantity of
measured variable from start to current time. There are many styles and designs of
each basic type, and various combinations of these types. Therefore, no detailed
maintenance procedure can cover all types, designs, and combinations. Maintenance
procedures depend not only on the type of receiver (indicator, recorder, or register), but
also on the type of transmission system used. It is recommended that maintenance
personnel study the manufacturer's instructions for detailed procedures, in addition to
following the basic maintenance procedures for indicators, registers, and recorders
summarized in Table 29.
Recorders. Recording instruments have all of the fundamental elements
of an indicator unit and, in addition, contain a clock mechanism (spring or electrical), a
chart, and a marking pen. Charts may be either circular or strip and are changed on
schedule by operating personnel. Maintenance procedures depend on the type of
transmission system employed, as well as on the design and other factors. Consult the
manufacturer's instructions for detailed procedures. General maintenance procedures
are included in Table 29.
Totalizers or Registers. This type of receiver has internal components
similar to those in recorders. In addition, it contains an integrator mechanism that
converts transmitted signals into a sum of the total quantity of material that has moved
past the point of measurement from the beginning of the measured period to the time of
observation. This total appears on a numerical register similar to an automobile
odometer. Clean, service, and adjust registers according to the manufacturer's
instructions on the same general schedule as recorders.