
Troubleshooting
2-3
B. Checkerboard pattern and the annunciators that are
on during normal operation.
C. Horizontal lines (pixels) of the first digit are se-
quenced.
D. Vertical lines (pixels) of the first digit are se-
quenced.
E. Each digit (and adjacent annunciator) is sequenced.
All the pixels of the selected digit are on.
5. When finished, abort the display test by pressing EXIT.
The instrument returns to the SELF-TEST MENU. Con-
tinue pressing EXIT to back out of the menu structure.
2.4.3 Character set test
You can also display the character set as follows:
1. Display the MAIN MENU by pressing the MENU key.
2. Select TEST, and press ENTER to display the SELF-
TEST MENU.
3. Select FRONT-PANEL-TESTS, and press ENTER to
display the following menu:
FRONT PANEL TESTS
KEYS DISPLAY-PATTERNS CHAR-SET
4. Select CHAR-SET, and press ENTER to display the
character set. Press EXIT to abort the test.
2.5
Diagnostics
The Model 2002 has diagnostic test modes that allow you to
“freeze” instrument operation letting you check logic levels
on the various control registers. The known bit pattern at
these registers can then be used for signal tracing through the
unit.
Perform the following steps to use DIAGNOSTICS:
1. Display the MAIN MENU by pressing the MENU key.
2. Select TEST, and press ENTER to display the SELF-
TEST MENU.
3. Place the cursor on DIAGNOSTICS, and press ENTER.
4. Use the range keys to scroll through the various diagnos-
tics phases summarized in Table 2-1.
5. To view A/D counts, press the right arrow key.
6. When finished, press EXIT three times to back out of the
menu structure and return to the normal measurement
mode of operation.
2.6
Control register bit patterns
2.6.1 Control register ICs
The four control registers are made up of the following ICs:
AD_STB:
U811, U810, U809
MUX_STB:
U206, U207
R1_STB:
U203, U222, U224
R2_STB:
U400, U406, U411, U432
2.6.2 Normal operation bit patterns
Table 2-2, Table 2-3, and Table 2-4 are provided to allow you
to check logic levels on the R1_STB, R2_STB, and
MUX_STB shift registers for each basic measurement func-
tion (DCV, ACV, DCI, ACI,
Ω
2 and
Ω
4) and range. The
known bit pattern at these registers can then be used for sig-
nal tracing through the unit.
To use these tables, simply place the instrument in the desig-
nated function and range and check the output of the shift
registers for the indicated bit pattern. The bit patterns in these
tables assume the following conditions:
NPLC > 0.01
AC Type = RMS or Average
Offset Compensated Ohms = Off
Current Measurement Mode = Normal (No In-Circuit I)
Table 2-1
Diagnostic bit patterns
Mode
Register IC*
U206
U207
Zero X1
Zero X5
Zero X50
Sense Zero X1
Sense Zero X5
Sense Zero X50
2V Reference
7V Reference
20V Zero
20V Reference low
20V Reference high
01110000
10110000
11010000
01110000
10110000
11010000
10110000
01110000
01110100
01110001
01110010
00001111
00001111
00001111
00011011
00011011
00011011
01010111
00110111
01101111
01101111
01101111
*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.
Содержание 2002
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