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Why does the B&S CMM light pen not work with an amber CRT?

Bill in PA

Hot Rolled
Joined
Jan 25, 2011
Location
Fairfield, PA
B&S MicroVal CMM

The current CRT has a blue and white display. I bought an amber CRT as a spare. The amber display is crisp and bright but the light pen does not work with it. Anyone know why? I was hoping to use the amber one as the other CRT cuts off part of the display.

Thanks,

Bill
 

thermite

Diamond
B&S MicroVal CMM

The current CRT has a blue and white display. I bought an amber CRT as a spare. The amber display is crisp and bright but the light pen does not work with it. Anyone know why? I was hoping to use the amber one as the other CRT cuts off part of the display.

Thanks,

Bill
If not "visible light" passband, the light pen sensor may be towards Ultra-Violet range.... whereas you may need one towards Infra-red range.

Most sensors have rather narrow optimally efficient ranges, some extremely so.

I assure you yellow/amber can WORK. Light pens are simple. It's the timing at the system end that gets hairy if one needs any sort of repeatable fine-granularity, accuracy-wise.

One of the first-ever light pens - highly classified at the time - was on the AN/GSA-51 (Burroughs D800) "Radar Range Computer" 'TID" display as adapted to NORAD "BUIC" Weapons Director consoles, very similar colour phosphors. Far older AN/FSQ-7 also used amber, but the display was vector, not raster, and a trackball and cursor was used. So "no" neither Xerox/PARC now Apple "invented" the "mouse". A crossbreed of IBM Research, MIT, (MITRE) ...and the Devil .... had already been there, done that.....and "Classified" the tee shirt.

:D
 
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Scottl

Diamond
Joined
Nov 3, 2013
Location
Eastern Massachusetts, USA
It may well be that the sensor in the pen will not respond to that wavelength or it could be a filter in front of the sensor causing the issue. Either way, not generally a quick and easy fix available.
 

Scottl

Diamond
Joined
Nov 3, 2013
Location
Eastern Massachusetts, USA
It does have an anti-glare screen.

Bill
I suspect it's more likely the wavelength of the light. Amber is more yellow whereas white contains all colors.

Possibly there is a contrast adjustment somewhere for the pen that could be tweaked. Are there any user groups for these machines?

As Gordon suggested, 1st solution would be to adjust the current monitor. I'm assuming this is an analog monitor and they always have adjustments for screen size and position.
 

Bill in PA

Hot Rolled
Joined
Jan 25, 2011
Location
Fairfield, PA
I suspect it's more likely the wavelength of the light. Amber is more yellow whereas white contains all colors.

Possibly there is a contrast adjustment somewhere for the pen that could be tweaked. Are there any user groups for these machines?

As Gordon suggested, 1st solution would be to adjust the current monitor. I'm assuming this is an analog monitor and they always have adjustments for screen size and position.
The amber monitor is EGA and displays correctly. I believe the other monitor is CGA. It cuts off the additional horizontal lines. The width cannot be corrected enough too.

The light pen works with the CGA monitor switched to green also.

I'll have to keep looking for an EGA monitor that is not amber.

Thanks,

Bill
 

thermite

Diamond
The amber monitor is EGA and displays correctly. I believe the other monitor is CGA. It cuts off the additional horizontal lines. The width cannot be corrected enough too.

The light pen works with the CGA monitor switched to green also.

I'll have to keep looking for an EGA monitor that is not amber.

Thanks,

Bill

Plug & interface have very little to do with it.

"Hollow State" era CRT's were coated with a "cocktail" of phosphors. The goal was to balance efficiency vs dot-size, brightness, & duration so the information lasted long enough to be seen well at the scan rate - but not so long as to leave streaks and afterglow blur. Obviously, Oscilloscopes wanted different coatings than TV or text-mostly monitors. Monitors also used coloured filters, user side of the screen - some green or amber actually having "white" phosphers..

As they are no longer "primary use" technology, nor common, you'll probably find a workable solution FASTER by seeking more than one light pen (sensor) and trying it.

Sensor - or whole light-pen, is much easier to SHIP without damage, and probably CHEAPER by more than just a little bit, than an obsolete display head, too.
 
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