Stanford Research Systems SR830, Manual

Page: 71 / 177

4-18
Front Panel
Reference
[Phase]
Pressing this key displays the reference phase shift in the Reference
display. The knob may be used to adjust the phase. The phase shift
ranges from -180° to +180° with 0.01° resolution.
When using an external reference, the reference phase shift is the phase
between the external reference and the digital sine wave which is multi-
plying the signal in the PSD. This is also the phase between the sine
output and the digital sine wave used by the PSD in either internal or
external reference mode. Changing this phase shift only shifts internal
sine waves. The effect of this phase shift can only be seen at the lock-in
outputs X, Y and
θ
. R is phase independent.
Auto Phase
Pressing [AUTO PHASE] will adjust the reference phase shift so that the
measured signal phase is 0°. This is done by subtracting the present
measured value of
θ
from the reference phase shift. It will take several
time constants for the outputs to reach their new values. Auto Phase may
not result in a zero phase if the measurement is noisy or changing. If
θ
is
not stable, Auto Phase will abort.