Model 1835-C - Newport Corporation

2.3.5 ZERO, Offset Subtraction
This key turns offset subtraction on and off. When turned on, the ZERO
annunciator lights and the last signal reading is saved as S d
and subtracted
from all subsequent signal readings S. This causes subsequent signal calculations
(and the display) to use the value S-S d
instead S.
Offset subtraction allows one to remove the effects of ambient DC signals, by
zeroing the display before making a measurement. A second ZERO key press
turns off the ZERO annunciator and stops offset subtraction.
2.3.6 AUTO, Automatic Gain Ranging
The AUTO key toggles automatic signal ranging on and off. When on, the
AUTO annunciator lights and the signal range (amplifier gain) is adjusted to
utilize maximum analog-to-digital converter resolution. When AUTO is turned
off, the AUTO annunciator is turned off and the signal range is left in its
current state.
Signal range can be manually controlled by the , arrow keys. Pressing an
, arrow key when AUTO is on (and STATS, MENU and λ are off), turns
AUTO off and executes the manual range change. See RANGE, Section 2.3.10.
Signal range changes will not often coincide with observable changes to the
display value as the display is scaled by the detector responsivity and so must
adjust independently. Signal range gains will occur in 1 decade steps when
auto ranging and 1 or 1 ⁄2 decade steps (depending on MODE) when manual
ranging.
When auto ranging in CONT PULSE mode, the arrival rate of pulses must be
above 1 Hz. In P-P CONT mode, the arrival rate of peaks must be above 50 Hz.
AUTO gain ranging is not allowed in SNGL measurement modes. When exiting
a SNGL measurement MODE, AUTO will turn back on if it was on when the
SNGL measurement mode was entered. (See MODE, Section 2.3 12)
2.3.7 STO REF, Store Reference Value
STO REF causes the last measurement D to be stored as D ref
for subsequent
use in relative measurement calculations. When units are relative, REL, the
displayed value is the ratio D/D ref.
When units are logarithmic relative, dB, the
displayed value is the function 10 log (D/D ref
). D ref
is always a power reading
stored in the units of Watts.
Press STO REF to cause a new D ref
to overwrite the existing D ref
value and show
this new D ref
in the message display area. D ref
will be displayed until overridden
by an ESC, λ, RANGE or MENU keypress. STO REF can be pressed at any
time.
NOTE
When not using remote interface operation and when displaying relative dB
or REL measurements, the message display area will show the STO REF value
used in the calculation.
7