HP 3478A Technical Manual page 26

3478A 3478A
time is 1/60 second (or 1/50 second for the 50Hz op- time is 1/60 second (or 1/50 second for the 50Hz op-
tion), which is called I PLC (Power Line Cycle). In the 3 tion), which is called I PLC (Power Line Cycle). In the 3
1/2 digit mode, the time is 1/600 second (or 1/500 1/2 digit mode, the time is 1/600 second (or 1/500
second for the 50Hz option) which is .1I PLC. In the 5 second for the 50Hz option) which is .1I PLC. In the 5 1/2
digit mode, the 3478A takes 10 readings using the 4 1/2 digit mode, the 3478A takes 10 readings using the 4 1/2
digit mode and averages them together for an extra digit digit mode and averages them together for an extra digit
of resolution. This takes a time of 1/6 second (or 1/5 of resolution. This takes a time of 1/6 second (or 1/5
second in the 50 Hz option) which is 10 PLC. For more second in the 50 Hz option) which is 10 PLC. For more
information on run-up time and the A/D Converter, refer information on run-up time and the A/D Converter, refer
to this manual's Section VII (Service Group F, A/D to this manual's Section VII (Service Group F, A/D
Converter theory of operation). Converter theory of operation).
3 3 - - 5 5 7 7 . . A A u u t t o o z z e e r r o o
3-58. 8. 3-5 The The Aut Autoz ozero ero Fun Functi
compensate for offsets that may be present in the compensate for offsets that may be present in the
multimeter's internal circuitry (DC/Ohms Input Amplifier, multimeter's internal circuitry (DC/Ohms Input Amplifier,
A/D Converter, etc). The method used is to temporarily A/D Converter, etc). The method used is to temporarily
connect the input of the amplifier to ground (the INPUT connect the input of the amplifier to ground (the INPUT
LO Terminal) and make a measurement (the INPUT HI LO Terminal) and make a measurement (the INPUT HI
Terminal is open at this time). The off- set reading is Terminal is open at this time). The off- set reading is
then stored into the 3478A's internal memory. After that, then stored into the 3478A's internal memory. After that,
the short is removed and a regular input measurement is the short is removed and a regular input measurement is
made. The offset reading is then subtracted from the made. The offset reading is then subtracted from the
input reading and the compensated reading is displayed. input reading and the compensated reading is displayed.
3-5 3-59. 9. The The Aut Autoz ozero ero Fun
3478A is turned on and after doing a Self-Test (see 3478A is turned on and after doing a Self-Test (see
paragraph 3-60). paragraph 3-60). The feature can be disabled by The feature can be disabled by
pressing the blue Shift button and then the INT/TRIG pressing the blue Shift button and then the INT/TRIG
but- ton. The "AZ OFF" annunciator on the display will but- ton. The "AZ OFF" annunciator on the display will
light, showing that the function is off. After the function is light, showing that the function is off. After the function is
turned off, the multimeter immediately takes an offset turned off, the multimeter immediately takes an offset
reading and stores it into memory. This last reading is reading and stores it into memory. This last reading is
then subtracted from the input measurements that follow. then subtracted from the input measurements that follow.
Since no more offset readings are taken, the reading Since no more offset readings are taken, the reading
rate of the 3478A is faster (up to twice as fast). If a rate of the 3478A is faster (up to twice as fast). If a
range, function, or digit change is made, or an at- tempt range, function, or digit change is made, or an at- tempt
is made to calibrate the 3478A, a new offset reading is is made to calibrate the 3478A, a new offset reading is
taken. With Autozero off, the 3478A's input circuitry taken. With Autozero off, the 3478A's input circuitry
remains in a static state. This is useful when making remains in a static state. This is useful when making
measurements in extremely high impedance circuits measurements in extremely high impedance circuits
where the internal switching transients of the 3478A may where the internal switching transients of the 3478A may
affect the reading accuracy. affect the reading accuracy.
The 3478A's long term stability may be affected, The 3478A's long term stability may be affected,
if the Autozero feature is disabled. if the Autozero feature is disabled.
3- 3-60 60. . Self lf-T -Tes Se est t Re Rese set t Op
3-6 3-61. 1. The 347 The 3478A u 8A uses ses an I
its display and internal circuitry. The multimeter goes its display and internal circuitry. The multimeter goes
through the test at turn-on and also when the Self-Test through the test at turn-on and also when the Self-Test
is selected. The test can be selected by pressing the is selected. The test can be selected by pressing the
blue Shift button and then the SGL/TRIG button. When blue Shift button and then the SGL/TRIG button. When
the the
ction on of t of the 3 he 3478 478A is A is use
Functi ction i on is en s enabl abled w ed when
NOTE NOTE
Oper erat atio ion n
an Inte nterna rnal Se l Self- lf-Test Test to c
test is selected from the front panel, all the segments of test is selected from the front panel, all the segments of
the display (except the upper dots of the colons) are on the display (except the upper dots of the colons) are on
for about five seconds. After that, the display may for about five seconds. After that, the display may
1/2 indicates a certain message or characters for about 1/4 indicates a certain message or characters for about 1/4
second. second.
multimeter's remote (HP-IB) address is displayed for multimeter's remote (HP-IB) address is displayed for
about one second as "HPIB ADRS. dd" (where dd is the about one second as "HPIB ADRS. dd" (where dd is the
address code). The 3478A then resets to its turn-on state address code). The 3478A then resets
(see paragraph 3-7 (see paragraph 3-7), not the previous state. 3-62. If the
Self-Test fails, an error message will be displayed Self-Test fails, an error message will be displayed
indicating the type of failure. If there are multiple failures, indicating the type of failure. If there are multiple failures,
only one failure will be displayed. The 3478A then only one failure will be displayed. The 3478A then
attempts to operate normally (even if a test fails). If attempts to operate normally (even if a test fails). If
another failure is noted while trying to operate normally, another failure is noted while trying to operate normally,
the new failure will be displayed. This continues until the the new failure will be displayed. This continues until the
used to d to
test(s) passes or the instrument is taken out of the Self- test(s) passes or the instrument is taken out of the Self-
Test mode. Test mode.
E E r r r r o o r r M M e e s s s s a a g g e e
U. U.C. C. RA RAM M FA
RAM self test RAM self test
U.C. U. C. RO ROM M FA
POM self test indicating an error in the ROM POM self test indicating an error in the ROM
CAL R CA L RAM AM FA
CMOS RAM was unsuccessful CMOS RAM was unsuccessful
hen the the
UNCALI UNC ALIBRA
incorrect checksum showing that calibration is incorrect checksum showing that calibration is
needed needed
A: A:D D LI LINK NK FA
unable to communicate with the A/D unable to communicate with the A/D Converter
A:D SLO A:D SLOPE
proper conversion proper conversion
A: A:D D TE TEST
self-test. self-test.
3 3 - - 6 6 3 3 . .
3-6 3-64. 4.
calibrate the instrument; calibration is calibrate the instrument; calibration is done electronically.
A known good calibration source is applied to the A known good calibration source is applied to the
multimeter and the value of the known source is entered multimeter and the value of the known source is entered
into the instrument. A reading is then taken and into the instrument. A reading is then taken and
compared with the value entered. A Calibration Constant compared with the value entered. A Calibration Constant
is calculated (from the entered value) to correct the is calculated (from the entered value) to correct the
reading to the known value, and then stored into reading to the known value, and then stored into
memory. The correct readings are calculated using the memory. The correct readings are calculated using the
constants and then displayed. 3-65. There are two steps constants and then displayed. 3-65. There are two steps
in calibrating the 3478A. First, the front panel Calibration in calibrating the 3478A. First, the front panel Calibration
Switch has to be set to CAL/ENABLE. Second, the blue Switch has to be set to CAL/ENABLE. Second, the blue
Shift button and the LOCAL (CAL) button have to be Shift button and the LOCAL (CAL) button have to be
to chec heck k
pressed for each calibration step (e.g. press the buttons pressed for each calibration step (e.g. press the buttons
for the DC Volts Function's zero calibration and press the for the DC Volts Function's zero calibration and press the
buttons again for the function's full scale calibration). buttons again for the function's full scale calibration).
Refer to Sec- tion IV of this manual for the calibration Refer to Sec- tion IV of this manual for the calibration
procedures. procedures.
3-7 3-7
When When the the Self-Test Self-Test
), not the previous state. 3-62. If the
Table 3-2. 3478A Error Table 3-2. 3478A Error Message
FAIL IL The e 34 Th 3478 78A A ha
FAIL IL The e 34 Th 3478 78A A ha
FAIL IL An An at atte temp mpt t t to w
BRATED TED The The Cal Calibr ibrati ation
FAIL IL Th The i e int nter erna nal C
PE ERR ERR The A The AID C ID Conv onvert
ST FA FAIL IL Th The AID Co e AID Conv
C C a a l l ib ibr r a a t t io ion n
The The 347 3478A 8A doe does no s not h t have
TM 11-6625-3071-14 TM 11-6625-3071-14
is is completed, completed, the the
to its turn-on state
Message
D D e e f f i i n n i i t t i i o o n n
has s fa fail iled its int ed its inter erna nal l
has s fa fail iled it ed its s in inte tern rnal al
o wri rite te to to th the Ca e Cali libr brat atio ion n
on CMO CMOS S RAM RAM has has an an
l CPU PU (A (A/D /D Co Cont ntro roll ller er) i ) is s
Converter
erter i er is un s unabl able to e to do a do a
nver erte ter has fa r has fail iled it ed its s
ave any any adj adjust ustmen ments t ts to o
done electronically.