- Credit-card sized unit replaces shaping amplifier, pileup inspector
and multi-channel analyzer.
- Very high throughput:
>164,000 cps output count rate at 515mW (>1,000,000
cps for a periodic signal)
>328,000 cps output count rate at 560mW (>2,000,000
cps for a periodic signal)
- User settable gain and pileup inspection criteriapeaking times from
375ns - 96 microseconds.
- High level integration of control and acquisition parameters into
reconfigurable sets that are stored in non-volatile memory. Stored
sets are accessible with a single command to easily switch between
corresponding data acquisition modes.
- Accurate ICR and live-time reporting for precise dead-time corrections.
- Real multi-channel analysis, allowing for optimal use of data to
separate fluorescence signal from backgrounds
- Serial communications via RS-232.
- Alternate IDMA parallel interface supports a wide range of communications
including Universal Serial Bus (USB).
- Real-time control via 4 general purpose digital I/O lines, two of
which can be configured for industry standard I2C interface.
- Input (Analog)
Preamp Input: 1k Ohms input, voltage
range +5.0 V to -5.0 V standard. Works with common reset or resistor
feedback preamps of either polarity.
- Interface
Standard: RS-232 Serial communications with nearly any computer
or PDA, via the flat-flex interconnect
OEM Option 1: Analog Devices high-speed serial port (SPORT)
via the flat-flex interconnect
OEM Option 2: 16-bit IDMA bus; 4 general purpose digital I/O
lines, two of which can be configured for industry standard I2C interface.
Connected via a high-density board-to-board connector.
- Digital Controls (Set via EPP Port)
Gain Option a): Fixed gain for embedded applications
Gain Option b): 50X range controlled by 16 bit DAC. For general
use with preamplifiers with gains nominally in the 0.1 to 5.0 mV/keV
range. Adds 125mW to the power budget.
Shaping: Triangular/Trapezoidal.
Peaking times: 375ns - 96 microseconds. Adjustable dwell time
may be used to eliminate ballistic deficit effects.
Pileup: Set fast channel filter time, pulse detection threshold,
and fast channel pileup inspection test limits to achieve best results
in each situation.
Spectrum: 1K-8K bins, High/Low limits, bin widths.
- Data Outputs (via RS-232 Port)
Spectrum Size: 1024-8192 channels standard, more with optional
extra memory.
Other: collection livetime; total counts; pileup rejected counts;
baseline statistics.
- Power Requirements
+/-5 V @ 25mA
+3.3V @ 85mA - 150mA
- Dimensions
2.125" W x 3.375" L
The microDXP miniaturized circuit-board can easily
be incorporated into a variety of benchtop, portable, networked and
embedded x-ray and gamma-ray spectroscopy data
acquisition systems. In the first example the microDXP runs either on
the laboratory benchtop as a peripheral device under the control of
an x86 Personal Computer, or similarly in portable systems under the
control of a PDA. Only minimal user hardware design, and no microDXP
hardware or firmware modifications are required.
In the second example a more complex dedicated system is considered.
The I2C serial bus is used to control a ‘smart’ x-ray tube
and detector HV bias supply, and the auxiliary digital I/O drives electromechanical
or pneumatic components in real time based upon user defined metrics
of acquired data.
Example 1. General-Purpose Spectrometer
In this example the microDXP acts as a general-purpose
spectrometer, connected as a peripheral device under the control of
a host computer or PDA. No specialized data acquisition modes are required,
thus no firmware development is necessary. Some user hardware design
is however required.
XIA non-recurring engineering (NRE) required:
NONE.
User development required:
- To connect to the external host, only a simple
routing adapter interface unit is required to break out the microDXP
high-density internal connection to standard RS-232 and power connections.
At a minimum, this interface is a wire harness but could entail a
printed circuit board with a small number of passive components.
- Power supplies for the microDXP must be provided.
Optional voltage regulators for the analog circuitry are included
on the microDXP for systems in which high-quality power supplies are
not available.
- Some additional mechanical design, i.e. enclosure
design, may be necessary.
The microDXP, power supplies and ‘routing-adapter’
together constitute a spectrometer that can be connected to virtually
any controller with RS-232 communications. Note: The microCOM
interface board included with the development
kit falls into this category, though its large form-factor nearly
prohibits commercial use. XIA is currently developing a general-purpose
routing-adapter for standardized commercial operation of the microDXP,
ie. a more compact version of the microCOM Revision A board.
Fig. 1: A general-purpose
spectrometer incorporating the microDXP. A simple user-designed routing-adapter
interface connects the microDXP to the host computer/PDA and power supplies.
Example 2. Dedicated Embedded Spectrometer
This example considers a materials sorting application
where objects with certain pre-defined alloy ratios X, Y and Z are to
be separated from others. An x-ray source irradiates incoming samples,
and incident x-rays are collected by a solid-state detector connected
to the microDXP. The microDXP is configured to assert a combination
of its auxiliary digital I/O lines whenever the peak ratio X,Y, or Z
is detected. The digital I/O lines drive electromechanical or pneumatic
components in real-time to execute the appropriate mechanical operation,
e.g. put the recognized object in the desired bin. User controls are
limited to starting and stopping the system, and selecting one out of
a small number of operating modes. Power supplies for the microDXP are
also included. Finally, an external data port (e.g. RS-232) is also
included so that ratios corresponding to new alloys can be defined,
and new firmware uploaded without dismantling the hardware; or, alternatively,
the microDXP could periodically be run in full MCA mode under computer
control for diagnostic purposes.
This example demonstrates a system that uses a very small data acquisition
command set (i.e. ‘start run’ and ‘stop run’)
but that, conversely, requires customizations to the microDXP as well
as significantly more user-designed hardware.
XIA non-recurring engineering (NRE) required:
- Customized PIC microcontroller code is required
to implement the I2C peripheral device control.
- Customized PIC microcontroller code is required
to implement high-level data acquisition routines controlledthrough
the user pushbutton interface.
- Customized DSP code is required for peak ratio
calculations, possibly implemented in lookup tables.
- Minimal FiPPI (FPGA) code modification is required
to implement the auxiliary digital I/O functionality.
User development required:
- A more advanced interface unit is required
to break out the microDXP high-density internal connection to standard
RS-232, auxiliary and power connections. Still, this interface does
not involve many active components, i.e. the I2C and auxiliary digital
I/O are simply routed to additional connectors. The pushbutton interface
might include an additional microcontroller, but could be implemented
simply in logic.
- As drawn, the power supply is integrated on
the interface board, with the same requirements as in the previous
example. As stated there, optional voltage regulators for the analog
circuitry are included on the microDXP for systems in which high-quality
power supplies are not available.
- Again, some additional mechanical design, i.e.
enclosure design, may be necessary.
Fig. 2: A system with a fully
embedded host and user interface, with real time controls via the Auxiliary
digital I/O.
Designing the system described above using conventional
spectroscopy components would be a much more complex (and considerably
more expensive) task, when compared with the solutions proposed here.
Please contact the microDXP team at 
to discuss your application today!
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