Keithley 2002 Repair Manual

Troubleshooting
2-106
Test 500.7 — 2A DCA range
Type
Pass/Fail
Fault message 2A DCA range
Description The 7.2mA ohms source is switched in using the /OHMA control line at U223 and U220. U232
pin 2 to 3 connects the REFBUF to U233 pin 3. The 7.2mA current divides through Q211 and
Q212, then flows through Q213, R322, CR217, K201,R334 and R342. This point is the HI input
terminal to the DMM. The HI to AMPS jumper routes the current to the AMPS line through the
200mA range (Q223 and Q216 on), through R362 to common. 7.2mA through 0.1Ω generates
0.72mV at U225 pin 3. U225 is at unity gain so the same voltage is at DCA. DCA is switched
through U222 to the A/D MUX U226, and the gain is X50.
NOTE: INPUT LO and AMPS must be externally jumpered to run this test.
Drawing reference Analog Board; 2002-100
Components U220, U222, U223, U225, U226, U232, U233, and associated components.
Bit patterns
Bit pattern* Register
—U400—
01111011
—U811—
00001101
—U224—
10011111
—U432—
10000000
—U810—
00000011
—U206—
11010000
—U203—
10001110
—U411—
11111011
—U809—
11100111
—U207—
10101111
—U221—
01110111
—U406—
00000100
AD_STB
MUX_STB
R1_STB
R2_STB
*Bits associated with register IC terminals as follows:
QQQQQQQQ
87654321 87654321 87654321 87654321
IC pins: Q8=11, Q7=12, Q6=13, Q5=14, Q4=7, Q3=6, Q2=5, Q1=4.

Keithley 2002 Specifications

General

Brand	Keithley
Model	2002
Category	Multimeter
Language	English