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5-22
Ratio and channel average programming examples
Example #1 — The following command sequence performs the ratio calculation using
primary channel 102 of the Model 7702. After READ? is sent, the Model 2790 must be
addressed to talk to return the result of the calculation.
*RST
FUNC 'VOLT'
ROUT:CLOS (@102)
RAT ON
READ?
Example #2 — The following command sequence configures channels 103 and 105 for
the ratio and channel average calculations. When channel 103 is scanned, the ratio calcula-
tion is based on DCV measurements of channels 103 and 123. When channel 105 is
scanned, the channel average calculation is based on DCV measurements of channels 105
and 125.
FUNC 'VOLT',(@103)
RAT ON,(@103)
FUNC 'VOLT',(@105)
CAV ON,(@105)
dB
Expressing DC or AC voltage in dB makes it possible to compress a large range of
measurements into a much smaller scope. The relationship between dB and voltage is
defined by the following equation:
dB
=
where: V
The instrument will read 0dB when the reference voltage level is applied to the input.
If a relative value is in effect when dB is selected, the value is converted to dB then REL is
applied to dB. If REL is applied after dB has been selected, dB has REL applied to it.
klqb
dB configuration
Remote programming must be used to configure the Model 2790 for dB measurements. It
cannot be configured from the front panel.
V
IN
------------ -
20log
V
REF
is the DC or AC input signal.
IN
V
is the specified voltage reference level.
REF
The dB calculation takes the absolute value of the ratio V
The largest negative value of dB is -160dB. This will accommodate a ratio of
V
= 1µV and V
IN
REF
Model 2790 SourceMeter
' One-shot measure mode.
' Select DCV function.
' Close channel 102.
' Enable the ratio calculation.
' Read the result of the calculation.
' Set 103 for DCV.
' Set 103 for ratio on.
' Set 105 for DCV.
' Set 105 for channel average on.
= 1000V.
®
Switch System Reference Manual
/ V
.
IN
REF
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