Name: Keithley 2002
Brand: Keithley
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Troubleshooting

2-103

Bit patterns

Test 500.3 — 7.2mA ohms/2mA DCA range

Type

Pass/Fail

Fault message 7.2mA ohms/2mA 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. For a more detailed description of the circuit

setup, see test 304.1. 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 2mA switch (U234 pin

11 to 10), through part of R295, R319, and R362 to common. 7.2mA through 100Ω generates

0.72V 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 multiplexer U226, and the gain is X1.

NOTE: INPUT HI 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—

00001111

—U432—

10000000

—U810—

00000011

—U206—

01110000

—U203—

10001110

—U411—

11111011

—U809—

11100111

—U207—

10101111

—U221—

10110111

—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.