30
The analog signal flow path is primarily determined by the responsivity units
of the detector. The numerator of these units indicates how the meter must
be configured in order to obtain a calibrated optical measurement. Analog
signal flow is independent of whether SNGL or CONT measurements are made.
Responsivity units and signal flows for the various detector families are listed
in Table 22.
Table 22 – Analog Signal Flow Paths.
Detector Family
Resp. Units
Mode
Amplifier Path
Peak-Peak
A/D Converter
Low-Power
A / W
DC
I
No
20,000 or 4,096
Low-Power
A / W
P-P
I , AC coupled
Yes
4,096
Low-Power
A / W
INTG
I
No
4,096
High-Power
V / W
DC
V only
No
20,000 or 4,096
High-Power
V / W
INTG
V only
No
4,096
Energy
V / J
PULSE
V only
Yes
4,096
3.3
Digitized Signal Flow
Signals that are captured by one of the analog-to-digital converters are further
processed as illustrated in the signal flow block diagram of Figure 10. Raw
signals are acquired by the analog-to-digital converters and have the units of
current or voltage depending upon how the input amplifier chain was config-
ured. These digitized signals move through a number of process steps which
may or may not alter the digitized value depending upon the operating state of
the meter. Each of these possible processing steps is discussed in their order
of occurrence.
Detector
Calib.
Module
Figure
9
DIG
Filter
Gain
ZERO
UNITS
ZERO
Reference
Responsivity
Map(s)
STO-REF
Reference
Remote
Interface
VFD
Display
STATS
Buffer
Data Store
Buffer
Front Panel
Figure 10 – Model 2835-C Digitized Signal Flow Block Diagram
Digital Filter
If the digital filter annunciator DIG is on, Section 2.3.4, the filter output is the
average of the most recent 10 digitized values. When less than 10 values have
been acquired since the last reset of the digital filter, the output is the average
of all the values received. The digital filter is reset when the Model 2835-C is
turned on and whenever the UNITS or the range changes or when the MODE
key is pressed.
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