12
Operation
2.2.1.1 Changing the CT Configuration
The current input of the Model 918B Phase Angle Multimeter is
designed for operation with a current transformer, which reduces the
measured current to a level that can be accommodated by the
instrument. The standard clamp-on current transformer included
with the 918B has a ratio of 1000:1. The step-down ratio of other
current transformers to be used in conjunction with the 918B is
dependent on the range of currents to be measured.
The 918B
accepts 20 milliamperes maximum
.
NOTE
The Model 918B Phase Angle Multimeter incorporates
special circuitry to compensate for impedance characteristics of
Arbiter Systems' current transformers. Use of current transformers
from other manufacturers can result in instability and/or
unsatisfactory operation.
The 918B includes a provision for changing the current transformer
configuration, should this become necessary. One possible scenario
necessitating this type of change would be as follows:
Example: Measuring 1000 Amps
In order to measure currents of up to 1000 Arms, one could use an
Arbiter Systems Model 09113A 1000:1 clamp-on current
transformer, which must be used in conjunction with a Model
09182A 100:1 current transformer. The resultant combined current
step-down ratio would be 100,000:1. With this combination, the user
would have to reconfigure the 918B from the 1000:1 standard ratio
to the 100,000:1 required by the new combination.
Procedure
1.
To change the current transformer configuration, first turn the
unit off.
2.
Switch the 918B power ON. There will be a momentary display
of the present ratio setting. The initial default display is "CT:
20A CLAMP-ON".
