HP Forum Archive 13

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48G display flicker Message #1 Posted by Ed Look on 23 Sept 2003, 1:44 a.m. For the first time ever, I was using my 48G in my car parked near a sodium vapor streetlamp. At many angles of view, the 48g's display flickers (not unlike an older or cheap CRT monitor on some older or cheap PC) under the illumination of the streetlamp. What's the primary line of Na? 5880 angstroms or something like that? Although, it must the the frequency of the lamp that's doing it, not the frequency of the light (what COULD that have to do with anything here?). It was annoying enough I had to move my head or the calculator so as not to see the flicker! What's the refresh rate, if such a concept applies, of the 48G's screen??

Re: 48G display flicker Message #2 Posted by Randy Sloyer on 23 Sept 2003, 7:17 a.m., in response to message #1 by Ed Look I don't know the exact scan rate but would suggest it is time to change your batteries. I have found most G's will flicker in 60hz light when batteries are low, this is well before the battery low light comes on. The effect is much more prononuced when the temperature approches freezing.

Re: 48G display flicker Message #3 Posted by David Smith on 23 Sept 2003, 10:31 p.m., in response to message #1 by Ed Look The LCD display on the calculator is a scanned display. The sodium vapor lighting flickers at 60Hz. This acts like a strobe light that produces a beat frequency with the scanned LCD display. Flourescent lights may show a similar display, but the phosphor in their tubes has a longer decay time than the sodium vapor lights, so the effect is not as noticeable.

Re: 48G display flicker Message #4 Posted by Ed Look on 23 Sept 2003, 10:50 p.m., in response to message #3 by David Smith No wonder this is not normally observable. The decay tail! I didn't realize that fluorescent lights' phosphors had such a long decay time. Well, here's a good use for slow switching!

Re: 48G display flicker Message #5 Posted by David Smith on 25 Sept 2003, 3:17 p.m., in response to message #4 by Ed Look FLourescent lights have gotten better over the years. You only need 1/60 of a second hold time. Some gas discharge bulbs (usually metal halides) have a phosphor coating also.

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