15
5.3
AC Wattmeter Circuit
Figure 5-3 shows the circuit used when the WATTS pushbutton is depressed and
the Break-In Plug is connected for the 300 watt range. In this position the arma-
ture of the meter is connected across the line through a series resistor and the
field coils of the meter are connected across the current transformer T1.
F
igure 5-3. Simplified Wattmeter Circuit, 300 Watt Range
5.4
Schematic Diagram
The simplified circuits shown in Figure 5-1, 5-2 and 5-3 together with the AMPS
and WATTS pushbuttons, are combined in the complete schematic diagram shown
in Figure 7-1.
5.5
Break-In Plug
The special Break-In Plug supplied permits connections across the line for volt-
age measurements and in series with the load for current measurements. These
connections are clearly shown in Figure 4-1. Figure 5-4 shows the cable connec-
tions within the plug.
Figure 5-4. Cross Section of Break-In Plug, Showing Cable Connections
–
–
BREAK-IN PLUG
AC LINE
BLACK
RED
LOAD
+A
15A
3A
T1
R6
FIELDS
ARMATURE
R5
+V
150V
R1
R2
300V
WHITE
BLACK
BLACK LEAD
RED LEAD
3
RD WIRE GROUND
RED LEAD
BLACK LEADS
WHITE LEAD (NEUTRAL)