3-2

When

the shutter is closed the generator

will

switch off, unless

another shutter

is

still

open in one

of the

other

tube shield positions. Alternatively. the generator can be

switched

off

manually

by

operating

the

GENERATOR 0 push-button. All lamps will extinguish. Before

the generator is switched off the power

to the X-ray tube should be reduced, by first turning the

mA control to minimum, and then the

kV control.

Any

generation of HT will be inhibited if

the

shutter does

not

fully close

after

a close

shutter

command.

Fig. 3.1. Opening the window shutter.

3.3.SHUTTER CONTROL

For camera work it is usual to control the exposure time of the film to X-rays by using a PW 1722 timer. Two

timers can be fitted: the left-hand timer will control the shutter of either window 1 or window 2, and the

other timer the shutter of window 3

or

4. This

paragraph

describes

the

automatic

and manual

control

of the

shutter operation.

 

 

 

 

 

 

 

 

 

 

 

 

 

When the camera

is

installed

on its

bracket in front of the required

exit

window

of

the tube shield, open the

shutter disc and push the camera forward until the collimator enters

the

hole in

the

disc. Ensure

that

the

microswitch button

on

the tube

shield

is

actuated

by the pin

or arm

of the camera.

 

 

 

NOTE: The space between the front of the collimator and the exit opening of the tube shield should be kept as small as possible to ensure that radiation does not escape. Take care that the filter disc is free

to move, and is not damaged.