64
Channel Chassis with Integrated Controller 5017
Description
The DTX-5017 Chassis Unit serves as the host
for all installed 5xxx and 6xxx series modules providing operating
power, analog signal input and output connections, digital
module control functions, and computer platform for the Graphical
User Interface (GUI). Configured as 16 slots accepting any
of the DTX-5000/6000 series modules allows for a mix and match
of signal conditioning functions. Commercial Off The Shelf
(COTS) computer hardware (Pentium processor) and Microsoft
Windows OS were selected to insure compatibility with future
technology trends and to facilitate product maintenance. Standard
10/100 baseT Ethernet is included for Web based applications
along with PC compatible keyboard, video and mouse (KVM) ports
for standalone operation. User interface and control software
allows for ease of setup as standalone instrumentation, operation
as a Web based appliance or integration as part of an automated
test system.
Design
Features
A compact 5U chassis was developed to house up to 16 four-channel
conditioning modules and a complete single board computing system.
Internal shielding separates digital computing hardware and
main power systems from conditioning modules reducing electrical
noise and controlling airflow within the chassis. In addition
a single shielded backplane is used to route all signal input
and output connections directly to each module eliminating internal
cabling or interface connectors as potential noise sources.
To verify channel operation and accuracy, an on-board program-
mable frequency generator can be switched into the input with
a high-accuracy 24 bit A/D converter used to calibrate the
analog outputs. Low temperature-coefficient components are
used to maintain system accuracy over a wide temperature range,
and all circuitry is housed in a shielded enclosure for improved
reliability and noise reduction.
COTS Technology
The 5000 Chassis uses a standard micro-ATX computer board as
the system controller with a Widows operating system. This board
contains an Intel P4 processor running at 1.7 GHz, 512 MB of
system RAM and two PCI bus slots for system expansion or future
enhancement. Also included are an Ethernet interface for remote
operation and keyboard, video and mouse ports for standalone
operation. Using a standard processor board allows the unit
to be used with a variety of monitors, printers, and other external
devices, and allows the system to be upgraded as technology
advances.
Mixed Signal Technology
The actual circuitry inside each module type varies, but they
all share a common design approach. The input signal is first
amplified to a usable level, and is then converted to a digital
signal using a high-speed 16-bit Analog-to-Digital converter.
This allows all gain correction and filtering to be done digitally,
thereby improving system accuracy and stability. A Digital Signal
Processor (one for each channel) uses stored offset and gain
calibration factors to correct the digitized data values, and
performs the requested low-pass filtering. The DSP also compares
the signal level to user-specified limits, and sets the color
and brightness of the front-panel Signal LED accordingly. After
signal processing has been completed, the digital value is converted
back to an analog voltage by a high-speed 16-bit Digital-to-Analog
Converter. A four-pole low-pass filter removes the digitizing
steps in the reconstructed signal, along with any high-frequency
noise, and an output buffer provides up to 50 mA of signal current
to the output load.
Digital Interface
A proprietary interface board is used to connect the CPU’s
PCI bus to a passive backplane. This board provides PCI bus
interface buffering and address decode for controller interaction
with individual modules and a mechanical interface between the
ATX motherboard and 5000 chassis backplane.
Power Supply
A single 300w low profile ATX-type switching power supply is
mounted in a shielded enclosure along side the main processor
board providing system level power to chassis components and
installed signal conditioning modules. Individual modules convert
this system level power into isolated power supplies for analog
circuit components reducing conducted EMI and further enhancing
front end performance. Using a readily available COTS power
supply with standard connectors allows for ease of replacement
or future upgrade.
Input/Output Connectors
All sensor input signals are routed from the rear connector
directly to each module through a shielded backplane. Isolated
7-pin Lemo connector or commercial RJ-45 input connector options
are available. The connector pins are soldered directly to the
passive backplane, and the signal conditioning modules also
connect directly to the backplane, avoiding the use of less-reliable
and more noise-sensitive cabling inside the chassis. The conditioned
voltage outputs from each module are returned through the backplane
directly to a DB25 connector in 8 channel increments. The use
of standard DB25 output connectors allows for direct cabling
to DataMAX II instrumentation recorders. Using the DTX-BNC adapter
allows the output signals to be routed to isolated BNC connections.
Routing all input and output signals through the back panel
eliminates internal cabling and potential problems associated
with multiple internal interface connectors.
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