THEORY OF OPERATION
4-18
Versapulse Select Service Manual
0621-499-01 01/94
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A small sample (≈0.2%) of each YAG pulse is deflected from the first surface of the first (synthetic) sapphire
wedge optic to an imaging mirror. The imaging mirror forms an image of the rod end on the ENERGY I
pyrodetector (located on the Single Solenoid PCB). The heat generated by this energy striking the
pyrodetector generates a small current, the integral of which is proportional to the energy in the pulse.
Transimpedence amplifier U1-1 converts the current to a voltage which is integrated by U1-7. U16-7 acts as a
peak hold circuit, charging C9 to the highest level seen out of the integrator (U1-7) for a given pulse. At this
point the ENERGY I signal is ready to be measured by the main and safety processors through the ADC.
The imaging mirror is used to provide a constant image size on the pyrodetector surface for different beam
sizes (the beam cross section trends smaller as pump energy increases). This provides a more consistent
energy sampling across the range of pulse energy.
After the value of the ENERGY I line is read the ENERGY I circuit must be reset before the next pulse is
delivered. To reset the circuit the main processor asserts the INTEGRATE line (high) to close U5 contacts 3 to
2 and 6 to 7. Contacts 3 to 2 closed resets the integrator. Contacts 6 to 7 closed discharges C9 to reset the peak
hold circuit.
R7,R8 & R9 are adjusted during servicing to calibrate the energy monitor circuit.
4.4.7 Touch Screen & Remote Control Circuits
The touch screen display and optional wired remote control module display information to, and receive
operator inputs from, the user. The touch screen is the primary user interface. The optional wired remote
control provides most operator displays and functions in a package that can be bagged and taken inside the
sterile field.
The touch screen display is an AC plasma display with an overlaid infrared matrix.
The remote control includes a dot matrix display and 7 push-buttons.
Refer to the Touch Screen Display & Remote Control Simplifed Diagram (Figure 4.6) and to the associated
schematics in Section 8. To update the touch screen display, the main processor writes the screen information
to the dual channel UART controller. The UART then transmits the data in serial form out on the TXA line to
differential Driver U95. U95 translates the single line input into a differential signal out on pins 2 and 3 to the
touch screen display. This screen information provides parameter and status indications and marks off areas
of the screen for user inputs.
At the touch screen, operator input is detected as an interruption of a matrix of vertical and horizontal
infrared beams transmitted and detected just above the surface of the display screen. The LEDs are arranged
in two rows; one row along the bottom of the screen and one row along the right side of the screen. Infrared
detectors are located along the two opposite sides (left and top) of the display. Each LED output is directed
across the screen to the input of its associated detector. When the user touches the screen, some of the hori-
zontal and vertical infrared beams above it are interrupted, and this information is transmitted through the
differential bus receiver to both the safety processor and main processor UARTs (RXA line), and then on to
the respective processors.
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