Fluke 6060B Instruction Manual page 90

THEORY OF OPERATION
3·22.
The Generator allows amplitude modulation depth programming from 0 to 99% with I %
resolution. However, the maximum calibrated A M depth i s 90%. Programming an AM
depth greater than 90% causes the 'UNCAL' indicator to light. When the combination of
signal amplitude and programmed AM depth exceeds + 13 dBm peak, the 'UNCAL'
indicator lights to warn you the output level is no longer guaranteed. Amplitude
modulation depth is programmed using the 8-bit AM DAC, with a setting of 200 on the
AM DAC corresponding to 100% AM modulation of the output frequency.
3-23.
Frequency modulation (FM) is programmable with three digits of resolution in the three
decade ranges. Table 40- 1 2, FM Ranges, lists the three ranges.
3-24.
The FM DAC is a !O-bit DAC programmed to the FM deviation in Hz divided by the
resolution. Table 40- 1 3 lists the settings of the FM DAC.
3-25.
At power-on, the Generator automatically self tests its digital and analog circuits. If the
Generator fails any self test, the test results arc automatically displayed as error codes.
Several special functions are available for additional tests. (See section 40- 1 6. ) Also, the
Generator microprocessor continuously monitors t wo status signals, UNL VL
(unleveled) and UNLOK (unlocked).
The self tests can also be invoked by using the (SPCL] [0][2] keys. The results of the self
test can be displayed in the four display fields with [SPCL] [ ! )[ ! ] keys and can also be
transmitted using the optional I EEE-488 Interface.
Self tests 1 through 5 are digital checks that indicate the general functionality of the
Controller assembly. Self tests 6 through 10 use the two status signals UNL VL and
UNLOK to test the general functionality of the R F circuitry.
During the self-test sequence all attenuators are programmed ON (maximum
attenuation) to prevent unwanted signals at the output. In addition, the Generator is
programmed to the internal frequency reference because the self tests fail if there is no
reference supplied.
The self-test error codes and descriptions are listed in Section 40. A brief description of
the different Generator self tests are described in the following:
Test 1 .
Test 2.
Test 3.
Test 4.
3-6
Amplitude Modulation
Frequency Modulation
FM Deviation
Self Test
The Generator RAM i s verified by writing data to each memory location
and checking that the same data can be read back. Both the off-chip
RAM and the on-chip RAM are tested in this way.
The data in each word of the two instrument software EPROMs is
successively summed and rotated by two. The result of this procedure is
compared with a checksum for each EPROM.
The data in each of the three calibration EPROMs (VCO, Output, and
Attenuator) is summed and compared with a checksum.
The IEEE-488 (if installed) is verified by the microprocessor writing d ata
to the IEEE-488 chip and then by reading it back to see ifthe response is
the one expected. The operator is given a report only if the test fails.
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