Figure 10-32.--Simplified sketch of a follow-up control showing application of a gear differential.

the other side of the differential. This second operation

METERING AND INDICATING

SYSTEMS

is known as the servo response.

When there is a difference between the input and

Metering and indicating systems provide

the output, the spider of the differential turns. As this

continuous information from remote sensors on the

happens, the spider shaft operates a set of controls

position, status, or condition of a particular system.

which control the action of the servomotor in such a

The sensors used in metering and indicating systems

way that the motor drives its side of the differential in

include switches, salinity cells, mechanical linkages,

a direction opposite to that taken by the input. That is,

synchros, pressure sensors, and various types of

the servo always drives to reduce the difference, or

temperature sensors. Indicator panels used with the

error, to zero.

systems include meters, dials, lamps, and other

While you may not work specifically with

indicators that provide a readout of the desired

mechanical computers as an IC Electrician, you will

information. Some systems include alarms, which are

see the various gears and linkages in many IC circuits.

actuated when predetermined conditions exist.

When working with mechanical gear trains, it will

help to look for the simple machines within the

The operation of some of the various metering

equipment; this will help in the understanding of the

and indicating systems will be discussed in the

whole complex machine and will enable you to more

quickly isolate trouble areas.

following paragraphs.

Figure 10-32.--Simplified sketch of a follow-up control showing application of a gear differential.