Keithley 2002, User Manual

Page: 98 / 366

Front Panel Operation
2-81
nel, and then close the channel and take a reading. The pro-
cess repeats until all channels in the list are scanned.
The instrument defaults to this selection if it detects a scan-
ner card on power-up.
EXTERNAL
This menu selection enables scanning with an external scan-
ner card located in a switching mainframe. This selection
operates in a manner similar to INTERNAL except that the
internal scanner is not used. When this menu item is selected,
the instrument will immediately change to the selected mea-
suring function for the first channel. When the multimeter is
triggered, it will take a measurement and then change to the
measurement function for the next channel. This process
repeats until all channels in the scan list are scanned.
The instrument defaults to this selection if it does not detect
a scanner card on power-up.
RATIO and DELTA
Either of these two selections configures the Model 2002 to
measure the two specified internal scanner channels and then
compute the ratio or difference (delta) between them. When
Table 2-40
SCAN OPERATION menu structure
Menu item Description
INTERNAL Enables internal scanning.
EXTERNAL Enables external scanning.
RATIO
MEASURE
REFERENCE
FUNCTION
Enables ratio mode (internal).
Selects measure channel.
Selects reference channel.
Selects ratio function.
DELTA
MEASURE
REFERENCE
FUNCTION
Enables delta mode (inter-
nal).
Selects measure channel.
Selects reference channel.
Selects delta function.
RATIO or DELTA is selected, the instrument will close the
scanner reference channel and then wait for a trigger. When
the reading is triggered, the unit will make a measurement on
the reference channel, switch to the measurement channel,
and then take a second measurement. After measuring the
measurement channel, the unit will compute and display the
ratio or delta value, and switch back to the reference channel
to wait for the next trigger. Note that the ratio mode uses 7-
1/2 digits of display resolution, but the channel number will
not be displayed.
The following options are available for RATIO and DELTA:
MEASURE:
This option is used to select the measure chan-
nel. After selecting MEASURE, place the cursor on the
desired channel and press ENTER.
REFERENCE:
This option is used to select the measure
channel. After selecting REFERENCE, place the cursor on
the desired channel and press ENTER.
FUNCTION:
This option is used to select the function.
After selecting FUNCTION, place the cursor on the desired
function (DCV,
Ω
2 or
Ω
4) and press ENTER.
Ratio and Delta computation:
During configuration, one
channel is defined as the reference channel, and a second
channel is defined as the measurement channel. Ratio and
delta are computed from signals measured on these channels
as follows:
2.11.6 Using SCAN to configure scan parameters
Once an internal or external scan list is enabled, you use the
SCAN key to configure internal or external scanning. The
menu structure of Figure 2-32 shows the procedure.
The procedure changes scan layer parameters in the trigger
model. When scanning is disabled by the EXIT key, the trig-
ger model is restored to its pre-scanning configuration.
Ratio
Measure
Reference
------------------------ =
Delta = Measure - Reference