ORTEC Easy-MCS, Hardware User Manual

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931054C / 1213 1. INTRODUCTION
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the ramp profile is stored as a digital image in half the memory. This limits the memory
length available for counting events to 32,768 channels when the ramp is active.
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External Trigger Mode In the external trigger mode, a positive TTL logic pulse
delivered to the Start Input will initiate the scan in the Easy-MCS. The scan can proceed
based on the internal dwell-time clock in the Easy-MCS, or the channel advance can be
implemented by supplying pulses to the Channel Advance Input.
Using the internal dwell time, the scan starts on the first edge of the internal 50-MHz
clock following the rising edge of the Start Input pulse. When the external channel
advance is used, the scan starts as the rising edge of the first channel advance input pulse
crosses its discriminator threshold, subsequent to the rising edge of the Start Input. The
external channel advance input includes a computer-controlled discriminator threshold
selectable from –1.6 V to +3 V in 1.5-mV steps. This discriminator permits adaptation to
a variety of signal sources at the external channel advance input. The minimum interval
between external channel advance pulses is 100 ns.
Quick Access to Multiple Spectra
The MCS-32 software allows you to view either the spectrum being acquired in the Easy-
MCS memory (MCS mode) or you can transfer the contents of the MCS memory to the
MCS-32 software’s buffer window (buffer mode). The full power to display and manipulate
can be applied to the spectra in either of these memories. Spectra can also be saved as disk
files for later recall (into the buffer window) and processing.
Full and Expanded Displays Reveal Quantitative Details
Two views of the selected spectrum are displayed. The box in the upper, right-hand corner
always shows the full spectrum. A region selected and marked on this small display is
expanded in the larger display for better resolution of details. Using the mouse, you can
move a marker through the spectrum to a feature of interest. Simultaneously, the computer
displays the horizontal coordinate for the channel designated by the marker position, and the
number of counts recorded in that channel. By default, the horizontal coordinate is displayed
as the channel number in the external dwell-time mode. In the internal dwell-time mode, the
default horizontal coordinate corresponds to the selected dwell time. The horizontal scale can
be easily calibrated in user-defined units through least-squares fitting to a linear, quadratic,
or cubic function. In that case, the marker position reads out in the calibrated units. Once the
system is calibrated, you can quickly toggle back and forth between the default and
calibrated units.
The marker also serves to paint regions of interest (ROIs) on the spectrum. Commands under
the Calculate menu then trigger the computer to display the centroid of the ROI, the gross
(total) counts in the ROI, and the net counts above background in the region.