PROPER USE OF MANOMETER
the inside surface; therefore, the top of the column has
a convex meniscus (shape). Water wets the surface
and therefore has a concave meniscus. A mercury
Fig. 2 Comparison of Column Height for
column is read by sighting horizontally between the top
of the convex mercury surface (Fig. 2) and the scale. A
water manometer is read by sighting horizontally
The U-tube manometer is a primary measuring device
between the bottom of the concave water surface and
indicating pressure or vacuum by the difference in the
height of two columns of fluid.
Should one column of fluid travel further than the other
Connect the manometer to the source of pressure,
column, due to minor variations in the inside diameter of
vacuum or differential pressure. When the pressure is
the tube or to the pressure imposed, the accuracy of the
imposed, add the number of inches one column of fluid
reading obtained is not impaired.
travels up to the amount the other column travels down
to obtain the pressure (or vacuum) reading.
Refer to Table 7 to convert manometer readings into
other units of measurement.
The height of a column of mercury is read differently
than that of a column of water. Mercury does not wet
ENGINE ELECTRICAL GENERATING SYSTEM
Whenever trouble is indicated in the engine electrical
condition usually indicates the voltage regulator is set
generating system, the following quick checks can be
too high or is not limiting the alternator output. A high
made to assist in localizing the cause.
charging rate to a fully charged battery will damage the
battery and other electrical components.
A fully charged battery and low charging rate indicates
normal alternator-regulator operation.
A low battery and low or no charging rate condition
could be caused by: Loose connections or damaged
wiring, defective battery or alternator, or defective
A low battery and high charging rate indicates normal
regulator or improper regulator setting.
A fully charged battery and high charging rate
Contact an authorized Detroit Diesel Allison Service
Outlet if more information is needed.