Clock, Initiated measurement mode – Agilent Technologies L4400 User Manual
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L4400 User’s Guide
8
L4450A 64-Bit Digital I/O with Memory and Counter
Initiated Measurement Mode
Measurements such as frequency, period, duty cycle, and pulse width
require an initiate command and a gate. The
SENSe:COUNter:INITiate
command is used to initiate (arm) the measurement. The measurement is
gated by either an internal (default) or external gate source. For
measurements the external gate acts like an external trigger which triggers
the internal gate timer.
The gate source is set using the
SENSe:COUNter:SOURce
command.
The default gate source is
INTernal
. The gate is the aperture over which
the signal data is gathered. When the gate is internal, the measurement
begins as soon as the
INITiate
command is received.
Since the measurements are all derived from the same basic measurement,
you can retrieve the measured frequency, period, duty- cycle, and pulse
width from the same initiated and gated measurement. For example, the
following commands set the counter to measure the input signal for 1 ms
using the internal gate. The frequency, period, duty cycle, and pulse width
are returned as floating point numbers.
CONF:COUN:FREQ 1e-3, (@1301)
SENS:COUN:INIT (@1301)
SENS:COUN:FREQ? (@1301)
SENS:COUN:PER? (@1301)
SENS:COUN:PWID? (@1301)
SENS:COUN:DCYC? (@1301)
The
CONFigure:COUNter:FREQuency
command parameter sets the internal
gate time (to 1e- 3 or 1 ms in the above example). You can also set the
gate time using the
SENSe:COUNter:GATE:TIME
command.
Clock
The general- purpose clock output is derived from the internal time base.
The output clock is divided down from the time base clock such that:
Clock Output (Hz) = (time base frequency)/(divisor)
The time base frequency is 40 MHz. The divisor can be an integer from
2 to 4
6
providing a range of 20 MHz to 10 Hz for the clock output.
The valid values for the clock output rate are: 20 MHz, 13.33 MHz,
10 MHz, 8 MHz, 6.667 MHz, ... 10Hz. The clock output frequency will round
to the nearest achievable frequency.
The commands used to control the clock output are:
SOUR:MOD:CLOC:FREQ {
SOUR:MOD:CLOC {OFF|ON|0|1},
You can obtain the rounded value of the currently set clock frequency
using the following query.