Re[6]: Lead Aprons in Dentistry

[tdc@ehssun.lbl.gov]

>I don't think I have seen a single high frequency dental unit, new or 
>otherwise.  I have captured waveforms on many units and they have all been
>single phase half wave self rectified type units.  If you know a make or
>madel for a high frequency dental unit, I would love to capture a
>waveform.

I'll double check and get back on this one.  I use an oscilloscope in my
surveys - so I know what the waveform is of the machine I am looking at.
BUT to be sure of make and model - I have to check!

>On some newer units, you can block the tube port, darken the lights, place
>a flourescent screen next to the tube head and get a bright flash where
>the housing leakage is at its worse.

WOW - of this I had NO idea!  Never checked for it!  When I do get
abnormally high leakage - I DO use a screen or film to track it down - but
here to for have only seen this in Cysto labs with very sloppy tube to
collimator transitions.

>Then you can go back with your ion chamber at a meter and get the
>instantaneous rate and the correct for the duty cycle.

Actually - I have always calibrated my IC survey meters for impluse
response and have appropriate correction factors.

>Also with D speed film many 7 mA machines have typical timer
>settings of 24 imp or 0.4 sec.

Ah - ok.  I was thinking technique factors or 90 to 100 kV units, half
wave, 15 mA.  That would explain the difference.