Keithley 2002 Repair Manual

Troubleshooting
2-21
2.11.4 Triggers tests
Triggers are controlled by the 5064 ASIC (U618). This component has seven trigger outputs
(STO1-STO7) and eight trigger inputs (STI1-STI8). Lines STI1-STI6 and STO1-STO6 are used
to control the system trigger bus, line STO7 is used for Meter Complete, and line STI7 is used
for External Trigger. STI8 is connected to the Group Execute Trigger signal (GET) of the 9914
IEEE-488 bus controller (U622).
Test 105.1 through 105.6 — System trigger bus
Type
Pass/Fail
Fault message
Trig link channel <n> open
(<n> = 1 to 6)
Description
System trigger inputs are normally pulled up to 5V through the protection diodes and 5.1k Ω re-
sistors (CR611-CR616, R648-R650 and R655-R657). The Model 2002 can generate a trigger on
any of the six trigger bus inputs by turning on the appropriate FET (Q602-Q607). These FETs
are controlled by system trigger outputs (STO1-STO6) of the 5064 ASIC (U618).
In test 105.1, STI1 is set up as the trigger input. The trigger 1 FET (Q606) is then turned on and
off through STO1, and it is verified that this trips the trigger circuitry in the ASIC. This test is
then repeated for trigger 2 through 6 for tests 105.2 through 105.6. Success indicates proper op-
eration of the trigger bus.
Drawing reference
Digital Board; 2002-140
Components ASIC (U618), FETs (Q602-Q607), diodes (CR611-CR616), and 5.1k Ω components resistors
(R648-R650, R655-R657).
Test 105.7 — External Trigger/Meter Complete
Type
Pass/Fail
Fault message
Shorted VMC/EXT trigger
Description
This test is similar to System Trigger tests 105.1 through 105.6 except that there is no internal
connection between External Trigger and Meter Complete. Consequently, the meaning of a fail-
ure is reversed from that of the previous trigger tests. A failure is registered if a trigger does oc-
cur. A failure indicates that a short exists between External Trigger and Meter Complete.
An alternate way to test these triggers is to externally connect a BNC cable from External Trig-
ger to Meter Complete. When test 105.7 is run, the short should cause the test to fail. If it does
not, a problem in the signal path exists.
Drawing reference
Digital Board; 2002-140
Components
External Trigger/Meter Complete signal paths.

Keithley 2002 Specifications

General

Resolution	8.5 digits
DC Voltage Accuracy	±0.0006%
Maximum DC Voltage	1000 V
Maximum AC Voltage	750 V
Maximum DC Current	3 A
Maximum AC Current	3 A
Connectivity	GPIB, RS-232
DC Voltage Range	100 mV to 1000 V
AC Voltage Range	100 mV to 750 V
Resistance Range	10 Ω to 1 GΩ
Model	2002
Category	Multimeter
Interface	GPIB, RS-232
AC Current Accuracy	±0.1%
Frequency Range	0.1Hz to 300kHz
Display	VFD
Type	Digital
Power Supply	100-240V AC, 50/60Hz
Current Range (DC)	100 μA to 3 A
Current Accuracy (DC)	±0.01%
Current Range (AC)	100 μA to 3 A
Current Accuracy (AC)	±0.1%
DC Current Range	100 μA to 3 A
AC Current Range	100 μA to 3 A