LeCroy PXA125, Руководство пользователя

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User Manual PXA125
1-6 Portrayal
Functional
Description
Detailed functional description is given following the general
description of the features and functions available with the PXA125.
Output Functions
Model PXA125 is completely digital. There are no analog functions
resident in its hardware circuits. Data has to be downloaded to the
instrument for it to start generating waveforms. The instrument can
generate a few standard functions such as sine wave, triangular
wave and square wave. Each time that a standard function is
required, the instrument calculates its coordinates and places them in
the waveform memory. Therefore, every time a standard function is
selected, minimal time is required for the controller to compute the
function and load its data to the waveform memory.
Frequency
Waveform frequency and sample clock are programmed with 10
digits, limited only by 1
µ
S/s. Frequency accuracy of the output
waveform is determined by the clock reference, CLK10, which
provides 100ppm accuracy and stability over time and temperature.
Amplitude
The output level may be programmed from 160 mV to 16 Vp-p into
open circuit, or 80 mV to 8 V into 50
Ω
. Offset may be applied to the
output to shift the signal either positive or negative. Offset and
amplitude are inter-related, so make sure you understand the offset-
amplitude ranges before you apply offset to your signal.
Trigger Modes Besides its normal continuous mode, the PXA125 responds to a
variety of trigger sources. The output waveform may be gated,
triggered, or generate a counted burst of waveforms. A built-in trigger
generator, having a programmable period can be used as a
replacement of an external trigger source. The internal trigger
generator can be programmed with resolution of 7 digits. The
PXA125 can be programmed to output triggers on one or more of 8
trigger lines that are connected to P2, as well as, be programmed to
respond to these same trigger lines.
Arbitrary Waveforms The Model PXA125 generates arbitrary waveforms with 14 bits of
vertical resolution. Any waveform it generates must first be loaded to
its waveform memory. The arbitrary waveform memory is a bank of
14-bit words. Each word represents a point on the horizontal
waveform scale. Each word has a horizontal address that can range
from 0 to 2,097,152 and a vertical address that can range from -8192
to +8191 (14 bits). Using a high speed clocking circuit, the digital
contents of the arbitrary waveform memory is extracted and routed to
the Digital to Analog Converter (DAC). The DAC converts the digital
data to an analog signal, and the output amplifier completes the task
by amplifying or attenuating the signal at the output connector.
Memory Segmentation There is no need to use the entire memory every time an arbitrary
waveform is generated. The waveform memory can be divided into