Transformer Ratio Meter

The Eltel ATRM-200 Automatic Transformer Ratiometer measures the transformation ratio of
transformers in a ratiometric circuit. As the measurement is conducted at low flux density, this
measurement is equivalent to the turns ratio of the transformer. Besides measuring turns ratio,
ATRM-200 also measures phase angle deviation between the tested windings. As a perfect
transformer should show no phase difference between the input and output, the measured phase
angle deviation is an indicator of possible shorted turns or poor core quality.
The instrument excites the High Voltage winding (HV) of the test transformer and measures the
output of the Low Voltage winding (LV) in a ratiometric circuit and displays the result on a 4½ digit
LCD indicator .
The ATRM-200 uses 36 volts at line frequency to excite the HV winding. The measurement is not
instantaneous but is conducted over a period that is equal to a whole number of line frequency
periods, thereby helps to eliminate line frequency interference.