8060A
Instruction Manual
5-22
5-25. Switch Decoding Self-Test
To select the switch decoding self-test, hold down the REL button while you
turn on the instrument. After the power-on self-test has been completed (the
display is .8.8.8.8), release the REL button. The instrument should now
indicate the switch decoding. To cancel the switch decoding self-test, turn
off the instrument.
The switch decoding self-test indicates how the software in the
microcomputer interprets the configuration of the eight switches and four
push buttons. Each function or range that may be selected corresponds to a
number that appears in one of the digit positions on the display (see Table 5-
6). Notice that if no range is selected, the microcomputer assumes the 200
(
µ
A, mV,
Ω
) range is selected.
In some cases it may be helpful to know that the microcomputer scans the
switches in order from SW5 to SW8 (there is no input for switch SW4, the
default range). The microcomputer assumes the first range switch detected as
being pushed in is the desired range. For example, if you press in both the
200V and 1000V switches while in dc voltage, the microcomputer assumes
you want the 200V range. There are two exceptions: diode test and
conductance. If the microcomputer detects that the 2 kΩ switch is selected, it
checks for the 20 kΩ switch (indicating diode test selection). If the
microcomputer detects the 200 kΩ switch is selected, it checks for the MΩ
switch (indicating conductance selection).
Also during the switch decoding self-test, the continuity indicator (the long
bar across the top of the display) indicates the state of the
continuity/frequency comparator. When the voltage at U3-4 (CM-) is less
than at U3-3 (CM+), the continuity indicator is on. When the voltage at U3-4
is greater than at U3-3, the continuity indicator is off. You can use this
feature to check the comparator when troubleshooting the continuity or the
frequency functions. R9 controls the setting of the comparator offset.
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