Model H11-LIN Sensor
October 2007:
Sensor Includes PHA Energy Output
The following link (DPC.htm)
to the Sensit Data Processing and Calibration technical document has
been expanded to include specific technical aspects of the new model
H11-LIN sensor. Calibration data will be added as soon as it is
available The information
presented covers most aspects of understanding erosion data acquisition.
You are free to copy, reproduce and distribute this document.
Tech Ref:
Oct 21, 2007
Backward Compatibility:
The new model H11-LIN provides the
same PC and KE outputs as previous Sensit H11B & H11C sensors. It
no longer provides
the seldom used toggled version of these outputs.
Model H11-LIN improvements:
Sensit PHA data
requires pulse height analyzer
This applies only to the new PHA
data output. The standard PC (particle count) and KE (kinetic energy)
data outputs remain the same as previous models. Acquiring pulse height data requires
a pulse height analyzer. The Sensit PHA output pulse may be input to any
compatible pulse height analyzer for processing and collection.
These units tend to be expensive and normally do not acquire a series of
spectrum. Sensit plans to produce a PHA module by the 1st quarter 2008
that will process and record up to 1000 spectrum each comprised of 256
channels of 16 bit counters.
Background A pulse height analyzer
(PHA) produces
a graphical representation of the spectrum of pulse heights. Units of
time are not applicable. The x-axis represents pulse height and the
y-axis is the number of counts at that pulse height. The longer a
PHA is allowed to acquire data, the greater the resolution of
information. For example; A peak will become increasingly defined.
The PHA
is most commonly used in the field of nuclear scintillation. It is
simply the counting and sizing of radioactive particle energy. The
energy spectrum of radioactive atomic particles clearly defines a
radioactive isotope by "signature" peaks.
Generic PHA instrument structure
A pulse height analyzer is an
instrument with a large number of counters. The number of counters
typically vary from 128 to 4095 or more. Each counter is assigned to a
small pulse height (voltage) range. Each counter is typically capable of counting 216 -> 220
counts
per channel (counter). Example: If the PHA input voltage range for incoming pulse heights
is 4.095 volts, and there are 4095 counters, a separate counter is
assigned to count pulse heights over every 1mV portion of the 4.095 Volt
range.
Sensit PHA data
The amplitude of each Sensit PHA
output pulse is proportional to the energy transferred from one particle
impact. A pulse height analyzer data acquisition module is being
developed to acquire the large amount of data produced.
Sensit expects to have a PHA module
available 1st quarter 2008. Alternatively, if your facility is
technically inclined, you could build your own pulse height analyzer.
The standard Sensit PC output pulse can be used as a sync pulse for
your PHA. All you need to do is build a PHA performing an A/D conversion
of the Sensit PHA output (0->4.095 Volts) within 40uS after the rising
edge of the PC output. Your A/D resolution (8, 10, 20 bit A/D)
determines the number of counters your memory must support. Use
this A/D value to address a memory location where you read the value in
that address, add one to it, and put it back. Thats all there is
to it, except for dumping the memory via RS232 or USB into your
computer. They are really quite simply in their elementary form.
Gain Selection
Note: The dynamic range of the pulse
height output covers fine to medium particle impact energies encountered
during typical erosion events. The total dynamic range (105)
of all possible eroding particle energies is too great to be covered by
a single linear A/D system so we incorporated the selectable gain (X1,
X10) to increase the sensors capability.