Cirrus SR22 Pilot Operating Handbook page 244

Section 7 Cirrus Design
Airplane Description SR22
The AMP pointer sweeps a scale from -100 to +100 amps with zero at
the 9 o'clock position. The amps indication is derived from current
transducers located in the MCU. Output from each alternator and BAT
1 is measured. The panel mounted AMMETER SELECT switch is
used to select the desired indication. When the engine is operating
and the ALT 1 and ALT 2 Master switches are 'on,' the ammeter
indicates the charging rate applied to the batteries. In the event the
alternators are not functioning or the electrical load exceeds the output
of the alternators, the ammeter indicates BAT 1 discharge rate.
Alternator ammeter indications are positive only.
Serials 1602, 1644, 1663 and subsequent: Main and Essential Bus
voltages are shown as text in the electrical data block located in the
mid-right section of the MFD and are also displayed in the voltage
parameters block located in the upper left corner of the PFD when
voltages fall outside typical operating parameters. The MFD and PFD
receive the voltage signals via the DAU as measured directly off the
Main and Essential Buses.
In the event Main Bus voltage is less than 24.5v or exceeds 32.0v the
MFD will display "Check Main Bus" in a yellow advisory box in the
lower right corner of the MFD.
In the event Essential Bus voltage is less than 24.5v or exceeds 32.0v
the MFD will display "Check Main Bus" in a red advisory box in the
lower right corner of the MFD.
Alternator 1 and Alternator 2 ampere output are shown as text in the
electrical data block located in the mid-right section of the MFD. The
MFD and PFD receive the amp signals via the DAU as derived from
current transducers located in the MCU.
In the event Alternator 1 or Alternator 2 ampere output is less than 2
amps for 20 seconds or more, the MFD will display "Check ALT 1" or
"Check ALT 2" respectively, in a yellow advisory box in the lower right
corner of the MFD.
28 VDC for the digital instrument operation is supplied through the 2-
amp ANNUN / ENGINE INST circuit breaker on the Essential Bus.
7-70 P/N 13772-001
Revision A7