ML0030 August 2009 Copyright 2009 Bitronics, LLC
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standard Megawatt/Megavar faceplate, 19.99 to 1999 megawatts can be accommodated.
For measurements outside this range, alternate faceplates are available with units of
Watts/Vars, kilowatts/kilovars, megawatts x1000/megavars x1000.
4.2 Calibration
Routine recalibration is not recommended, or required. However some drift or aging may
cause slight errors after years of use. Additionally, users may wish to have a WATT/VAR
meter "agree" with other instruments. To accommodate both these instances, a "Master
Gain" trimpot has been provided. This trim adjusts the overall scale factor by +/-10%, and
is accessed in the following manner:
1. Remove the four cover screws, and remove the front cover and gasket.
2. Remove calibration seal located in upper right-hand corner of the display board,
this will allow access to the trimpot located on the Analog Processing board.
3. Insert a small screwdriver through the opening, and into the slot of the screw on
the trimpot.
4. With the meter powered, AND WITH A PRECISION KNOWN INPUT, rotate the
screw clockwise to increase the measurement, or counter-clockwise to decrease the
indicated measurement. NOTE: Because these WATT/VAR meters are a full 2
elements, the instrument can be calibrated with a single phase source, all current
inputs should be connected in series, and all potential inputs should be connected in
parallel.
5. Remove the screwdriver, and replace the calibration seal.
6. Replace gasket, front cover and four cover screws.
The 0 to 1mA output will track the display, so recalibrating the display automatically
recalibrates the 0 to 1mA output. The 0 to 1mA output cannot be calibrated independently.
4.3 Self Test Modes
The WATT/VAR instruments are based on a microcontroller, and therefor can capitalize on
the power of such a device. One of the areas where the power of the microcontroller
enhances the overall performance of the instrument is in the area of "self-testing". The
WATT/VAR meters have several self tests built in to assure that the instrument is
performing accurately. Table I on the following page lists possible faults that would be
detected by the self tests, how the fault is indicated, the effects of the fault and any
necessary corrective actions.
4.4 Cleaning
Cleaning the exterior of the instrument shall be limited to the wiping of the instrument using
a soft damp cloth applicator with cleaning agents that are not alcohol based, and are
nonflammable, nonexplosive.
