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198-0853-02 Rev F
Loads
The load should be a resistor or set of resistors of approximately twice the required wattage to
prevent injury to personnel or equipment and to prevent significant temperature drift. The resistor
size is calculated so both the current and voltage can be calibrated with the same load. This can
be done because the calibration for the high end values takes place at 95% of rating. An
adjustable carbon pile load works well.
EXAMPLE LOAD CALCULATION:
Power supply rating is 12-100 or 12 Volts at 100 Amps.
The voltage developed across load should be approximately 12 volts at 100 amps current. To
determine the resistor value use Ohms law:
12Volts / 100Amps = 0.12 ohms
To determine the wattage use:
12 volts x 100 amps = 1200 watts
To calibrate the unit it will be necessary to connect a load resistor with a value of 0.12 ohms and
2400 watts (twice calculated wattage).
Optional Load Method (lower power resistors, 1200W vs. 2400W)
This method uses 2 different load values. When chosen properly the same set of resistors
can be rewired to work for both current and voltage calibration.
When calibrating the current settings, a value should be chosen which allows
approximately 50% of the voltage at the rated current of the power supply.
When calibrating the voltage settings, the value should allow for 50% of the current at the
rated voltage of the power supply. An adjustable carbon pile load works well.
Example Load Calculations:
Power supply rating is 12-100 or 12 Volts at 100 Amps.
Current Calibration Load:
The voltage developed across the load should be
approximately 6 volts at 100 amps average current. To determine the resistor value use
Ohms law:
6 Volts / 100 Amps = 0.06 ohms
To determine the wattage use:
6 Volts x 100 Amps = 600 watts
To calibrate the current settings it will be necessary to connect a load resistor with a value
of 0.06 ohms and 1200 watts (twice calculated wattage).