Dynalyzer – Digital Display/Printer
OPERATION MANUAL
11
External Trigger
The external trigger mode is provided for special applications. Any trigger signal must conform to
the voltage range (3-10 VDC) and duty cycle listed in SPECIFICATION.
Auto Trigger
AUTO trigger is the most useful when setting up filament circuits in the generator. The Display
operates as a DVM (digital voltmeter) for all inputs except exposure time and the display is
continuously updated. Auto triggering can also be used during fluoroscopic exposures particularly
when measuring automatic brightness control equipment effects on mA and kV.
When performing filament current measurements the current must maintain itself for 65 msec
because the rms converter in the Digital Display requires 65 msec to settle to its rated accuracy.
Most x-ray generators have the filament at rated current before the exposure begins, and this
enables the Digital Display to accurately measure the current during an exposure of less than 65
milliseconds.
In the AUTO mode the Digital Display provides one second updates of the filament current to
enable adjustment of the filament current controls.
The Dynalyzer III High Voltage Unit filament current sensor is frequency compensated from 20-
20,000 Hz. This enables the system to work with conventional x-ray generators, and with certain
CT generators employing high frequency power supplies. The response of the sensor falls off
rapidly beyond 20 kHz.
Manual Trigger
This switch will function with the trigger selector in any position. It is recommended that the
selector be in EXT if no external trigger source is being used. This pushbutton, when depressed,
causes the display to read the standby filament current. It can also be used during a fluoro
exposure to read kV and mA. If a printer is included in the system and is in the AUTO mode, the
data is printed.
KV and MA Trigger Mode Operation
The kVp and the mA trigger modes allow the user to either set a percentage of the prior exposure
at which the unit triggers by selecting PERCENT with the Trigger Mode select switch, or to select
an absolute trigger level by selecting the PRESET trigger mode.
In order to use the Percent mode, data must be stored in the Display memory. This data becomes
a ‘reference’ exposure, provided it exceeds 20 kVp (for kV triggering) or 40 mA (for mA triggering).
The following exposures in the series are triggered in this mode at a percentage level displayed in
the Percent/Preset window of the last previous exposure level. It is important to determine that any
noise produced by contactors or motor starters, etc. does not cause a false trigger. This can be
corrected by raising the trigger level (increasing the signal-to-noise ratio) to avoid the influence of
false triggers, or by turning the TRIGGER MODE switch to PRESET.
If the trigger level is too low the system may “latch-up” on noise. The system may appear to be
inoperative. Turn trigger level knob clockwise, and press RESET. The trigger level will jump to the
new value.
The minimum trigger level in PERCENT is set to the equivalent of 20 kV and 40 mA to minimize
noise problems. This value is independent of the percent selected.
