admium Voltmeter

Fig. 121 is a view of the special AMBU Voltmeter, which is designed to
be used specially in making Cadmium tests. Fig. 122 shows the Cadmium
leads. The four red lines marked "Neg. Charged," "Neg. Discharged,"
"Pos. Charged," and "Pos. Discharged," indicate the readings that
should be obtained. Thus, in testing the positives of a battery on
charge, the pointer will move to the line which is marked "Pos.
Charged," if the positive plates are fully charged. In testing the
negatives, the pointer will move to the line marked "Neg. Charged,"
which is to the left of the "0" line, if the negatives are fully
charged, and so on. Figs. 123, 124, 125 and 126 show the pointer
in the four positions on the scale which it takes when testing fully
charged or discharged plates. In each figure the pointer is over one
of the red lines on the scale. These figures also show the readings,
in volts, obtained in making the cadmium tests on fully charged or
completely discharged plates.

[Fig. 123 Voltmeter showing reading obtained when testing charged
negative; & Fig. 124 Showing reading obtained when testing
charged positives]

[Fig. 125 Voltmeter showing reading obtained when testing discharged
negatives; and Fig. 126 Showing reading obtained when testing
discharged positives]

If Pointer Is Not Over the "0" Line: It sometimes happens, in shipping
the instrument, and also in the use of it, that the pointer does not
stand over the "0" line, but is a short distance away. Should you find
this to be the case, take a small screwdriver and turn the screw which
projects through the case, and which is marked "Correct Zero," so as
to bring the pointer exactly over the "0" line on the scale while the
meter has no wires connected to its binding posts.

Connections of Cadmium Leads: In making Cadmium Tests, connect the
prod which has the cadmium fastened to it to the negative voltmeter
binding post. Connect the plain brass prod to the positive voltmeter
binding post. The connections to the AMBU Cadmium Voltmeter are shown
in Fig. 127.

Testing a Battery on Discharge

The battery should be discharging continuously, at a constant, fixed
rate, see page 265.

[Fig. 127 AMBU Cadmium Voltmeter]

Generally, on a starting ability test (see page 267), the positive
Cadmium readings will start at about 2.05 volts for a hard or very new
set of positives, and at 2.12 volts or even higher for a set of soft
or somew