4
Operating Instructions
Features
4. Digital Display
The VA-1A comes with 12 and 24 volt digital display back light control lines. The digital display
should be backlit all the time. This will allow it to be viewed easily in dim light. The digital display
is best viewed in high ambient light or direct sunlight.
Voltage will be displayed in 0.1 volt increments and a “V” annunciator will show in the display.
Amperage will be displayed in 0.1 amp increments for the VA-1A and any external shunted unit 60
amps and below (i.e., VA-1A-60 and below). For any external shunted unit above 60 amps (VA-
1A-70 and above) amperage will be displayed in 1 amp increments. Any time the Mode Switch is
in the “Amps” position, an “A” annunciator will show in the display.
Note: When the VA-1A (-XX) is mounted in the alternator lead and the engine is off, the VA-1A
(-XX) may display up to +/- 0.3 amps. This is due to any leakage current in the alternator and any
offset in the VA-1A (-XX).
5. Mode Switch
The Mode Switch sets the display between “Volts” and “Amps.” The setting of this switch will not
affect the operation of the “High Volts” or “Discharge” warning lights.
VA-1A Installed in the Battery Lead
The two common methods of installing the VA-1A or VA-1A-XX in the electrical system of your
aircraft are in the battery lead and in the alternator lead. Following are the operating characteristics
of the VA-1A installed in the battery lead.
1. Master On, Engine Off
The following describes the operating characteristics of the VA-1A installed in the battery lead
with the master switch on and the engine off.
With the Mode Switch in the “Amps” position, the VA-1A will display the electrical system load on
the aircraft. Since the engine is off, all of the current is being supplied by the battery. The VA-1A
will show a discharging condition (the “Discharge” light will be on) and display an accurate read-
ing of the total current drain from the battery. With all your electrical equipment off, this will be
around 2 to 6 amps. In this mode of operation any piece of electrical equipment can be checked
for proper operation by performing the following steps:
A. Note the amps reading on the VA unit.
B. Turn on the piece of electrical equipment you wish to check.
