1.2 Mechanical
1.3 Specification
Electronic Wattmeter
Chapter 1
The EW604 is housed
in
an
ABS plastic case made
in
two
halves, each secured
by
two screws
on
each side. The case
provides the
main
structural strength of the instrument. Removal
of the case gives access to
all
components. Without the cover
the EW604 consists of a horizontal
PWB
fixed
by
small plastic
brackets to the front and rear panels, providing a structure
strong enough for normal handling
and
maintenance. The low-
power dissipation of the EW604 obviates the need for
ventilation holes.
The controls, situated
on
the front panel
(see
fig
1.1) are:
Power
Green pushbutton power switch
Separate green power
ON
indicator
Current
Eight-position rotary range selector
Voltage
Eight-position rotary range selector
Terminals
Four 4mm
red
socket binding posts (two for connection to
supply and two for connection to the load) with mimic showing
metering circuits.
Meter
Mirror-scale moving-coil meter calibrated
in
watts.
Zero-
separate knob for electrical meter zero.
x2-
Pushbutton to increase sensitivity
Rev
- Pushbutton
to
reverse deflection
On
the rear panel are:
Current circuit-protection fuse holder with spare fuses.
'Three-terminal wattmeter'
(one
terminal common to voltage
and
current ranges) connected to four front-panel binding posts
so
that two are for connection to the 'supply' and two for connection
to the 'load'.
Power range
250mW
to
1
OkW
fsd.
Voltage ranges
Nominal
5,
10, 20,
50,
100, 200,
500
and 1000 volts.
6
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