CHAPTER THREE
With the unit operating, connect the AC source to be measured to TB1-8 and TB1-9 (50/60Hz
Measurement Input). Make sure that when plugging in the cable to the AC power source that it
is correctly polarized. For example, the pin labeled AC HI (50/60Hz Measurement Input - HI) is
plugged into the AC HOT receptacle. If this connection is reversed, the phase angle
measurement will be off by 180
o
.
The frequency measurement is made by counting the number of 50/60Hz sine waves occurring
between successive corrected 1pps pulses from the GPS receiver.
The phase angle measurement is made by calculating where the 1pps pulse occurs in relationship
to the 50/60Hz sine wave.
The error calculation is the accumulated time error based on whether the sine wave is fast or
slow. A time error offset can be entered when the 50/60Hz measurement is OFF, which is used
as a starting point for the error calculation.
Pushing keypad switch number one will program the offset. Note that an offset cannot be
entered until the measurement is stopped. OFF will appear in the lower right hand corner of the
LCD display. If the unit is not locked, ERR will appear. If the measurement is started, ON will
appear. Keypad switch number two will select “+” (plus) and switch number three will select “-
” (minus). The number of seconds offset can then be entered using the keypad switches up to
99.999 seconds.
Pushing the number four key will stop the measurement, and OFF will appear on the LCD
display in the lower right-hand corner.
Pushing the number five key will start the measurement, and ON will appear in the lower right-
hand corner of the LCD display. If the unit is not locked, ERR will appear in the lower right
hand corner of the LCD display.
Pushing the number six key of the keypad selects either 50Hz or 60Hz. 50Hz or 60Hz selection
can only be done when the unit is not doing measurements. OFF is displayed in the lower right
hand corner of the LCD display.
3-20 ET6xxx ExacTime GPS TC & FG (Rev C) Symmetricom Inc
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