Lamar Technologies CA 1550 - Manual (Page 14)

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4. CHECKING THE AMMETER:
a) In order to check the ammeter, a load is necessary in order to draw current.
A battery may be used but if the battery is fully charged or is rapidly tapering,
it may be difficult to check the current. A discharged battery with the 4159
unit, when set to charge, or a charged battery with the unit set to discharge is
the most convenient. Also, a high wattage load resistor may be used for both
voltmeter and ammeter checks. The voltage adjust when the unit is in charge
may be used to verify both volts and amperes. A suggested resistor is about 2
Ohms, whereby 24 Volts will draw 12 amperes. Wattage should be 300 Watts
or higher, or as rated if fan-cooled.
b) Connect the test meter such as fluke 77/AN to the amps (MV) test
points. The test meter must be on the DC Millivolt scale.
5. CHECKING THE AMPERE-HOUR METER:
a) As with the Ammeter, a load is necessary to check the amp-hr meter.
b) If a battery is used, the amp-hr meter reads on Charge or Discharge
without a minus sign for discharge.
Note: If the 4159 Charge / Discharge Switch (11) is toggled from Charge to
Discharge, the Discharge amp-hrs will subtract from the Charge amp-hrs. If the
amp-hr meter was reading Discharge, switching to Charge will subtract from the
Discharge reading.
c) To check the amp-hr meter accuracy, set the timer to 6 minutes. Connect
a resistive load in charge, or battery in Discharge for a Constant Current of 10.0
amperes. This will supply 60 ampere minutes or 1 ampere hour. The amp-hr
meter should read 1.0 ampere hours at the end of 6 minutes. The accuracy will be
affected by any variation in setting-up this procedure, plus the inherent instrument
accuracy of + - 2%.