Temperature Sensor Test - Keithley 2002 Repair Manual

2.11.8

Temperature sensor test

Test 301.1 — Temperature sensor
Type
Fault message
Description
Drawing reference
Components
Bit patterns
Pass/Fail
Temperature sensor
The temperature sensor is U205. Pin 1 of U205 is switched through U222 pin 12 to pin 3 of
U226. The X1 gain is achieved by closing U227 pins 2 to 3 with /X1 low. R274 is in the feedback
path of U226. The output of U205 is approximately 10mV per degree Celsius. For example, if
the ambient temperature is 25°C, the output would be 250mV. The measurement at the A/D con-
verter is therefore dependent on the ambient temperature. For the purpose of this test, the limits
of the measurement are 400mV ±400mV. These limits account for the entire specified range of
operating environments.
Analog Board; 2002-100
U205 and associated components.
—U811—
00001101
—U224—
00010111
—U400— —U432—
01111011 10000000
*Bits associated with register IC terminals as follows:
Q Q Q Q
87654321 87654321
IC pins: Q8=11, Q7=12, Q6=13, Q5=14, Q4=7, Q3=6, Q2=5, Q1=4.
Bit pattern*
—U810—
00000011
—U206—
01110000
—U203—
10001110
—U411—
11111011
Q Q Q Q
87654321 87654321
Troubleshooting
Register
—U809— AD_STB
11100111
—U207— MUX_STB
00001111
—U221— R1_STB
11101001
—U406— R2_STB
00000100
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