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possible. If R is less than 0.5% of full scale, the
phase output defaults to zero degrees.
The Phase Output may not be expanded and the
OFFSET keys do not offset the Phase Output.
However, the Phase Output can be offset using
the Reference Phase shift.
The Reference Phase shift, which may be
adjusted via the phase controls in the reference
section, rotates the lock-in's internal coordinate
axes relative to the reference input. The Phase
Output is the phase difference between the signal
and the lock-in's coordinate system. For example,
if a signal exactly in phase with the reference input
is being measured and the Reference Phase shift
is zero, the Phase Output will be zero also. This is
because the lock-in coordinate system is in phase
with the reference input and signal. If the
Reference Phase shift is set to +45 degrees, then
the lock-in coordinate system rotates to +45
degrees from the reference input. Thus, the
reference input is now at -45 degrees from the
lock-in coordinate axes. Since the reference and
signal are in phase, the signal is now at -45
degrees with respect to the lock-in coordinates
and the Phase Output will be -45 degrees.
The sum of the Reference Phase shift and the
Phase Output is the absolute phase difference
between the signal and the reference input.
Therefore, the Phase Output may be offset to zero
by adjusting the Reference Phase shift. This is
sometimes necessary when the Phase Output is
near 180 degrees and varies between +180 and -
180 degrees.
Output Channel 2
The CHANNEL 2 output is available at the right
hand OUTPUT BNC connector. The output
parameter is selected by the DISPLAY setting and
can be Y, Y OFST, Ø (phase), Ø (phase), Y
NOISE, or X6 (ext D/A). All outputs are ±10V full
scale when the EXPAND is off. With the EXPAND
on, the output is multipled by 10, effectively
increasing the full scale sensitivity by 10. (Ø and
X6 may not be expanded). The Ø (phase) output
is 50 mV/deg (20 deg per Volt) up to ±9 V (±180
deg). The output impedance is <1Ω and the
output current is limited to 20 mA.
The right hand analog meter always displays the
CHANNEL 2 OUTPUT voltage. Accuracy is 2% of
full scale.
The CHANNEL 2 LCD display provides a read-out
of the displayed parameter in real units. The scale
of the displayed quantity is indicated by the four
scale LED's to the right of the display. This read-
out auto ranges and will reflect the sensitivity
added when the EXPAND function is on. When
displaying X6, the scale LED's are off and the
units are volts.
Rel Channel 2
Every time the REL key is pressed, the displayed
parameter is offset to zero. This is done by
loading the displayed parameter's offset with
minus one times the present output. If the output
is greater than 1.024 times full scale, the REL
function will not be able to zero the output. In this
case, the OFFSET ON LED will blink and the
offset value will be set to its maximum value.
The REL function and the manual OFFSET are
both ways to enter the offset value. After using
the REL key, the offset may be adjusted using the
manual OFFSET.
When the DISPLAY is Y, Y OFST, or Y NOISE,
the REL key sets the Y OFFSET (which affects
the Y (RSINØ) output). If Y NOISE is being
displayed, the REL function zeroes Y and the
noise output will require a few seconds to settle
again.
The REL key zeroes the X6 output when the
DISPLAY is D/A.
Auto Phase
When the DISPLAY is Ø (phase), the REL key
sets the Reference Phase Shift to the absolute
phase difference between the signal and the
reference. This is done by setting the Reference
Phase Shift to the sum of the Reference Phase
Shift and the present Phase Output. After auto-
phase is performed, the Ø output will be 0 deg, R
will be unchanged, X will be maximized, and Y will
be minimized.
Offset Channel 2
The OFFSET section controls the manual offset.
The offset is turned ON and OFF using the upper
key in the OFFSET section. When the offset is
ON, the lower two keys are used to set the amount
of offset. A single key press will advance the
offset by 0.025% of full scale. If the key is held