HP48GX newcomer


Hey all,

Well, I buckled down and got the 48gx, it appears to be the black screen, but have any of you noticed a 'pulsing' of the screen. Its barely noticeable until you turn the contrast really dark. Just curious, this thing's gotta get me through my BSME! ...saving the 32sii in a dry cool box for the eventual PE fiasco.

Any new-user tips from you all?



I think the pulsing depends on the type of ambiant lighting. Yes, mine has it also when the contrast is turned up.



Someone correctly pointed out on this forum that the refresh rate on 48G screens are a bit over 64 Hz so that if a light has frequency of 60 or so Hz, then the interference "pulsing" is seen.


Normal bulbs pulse at 2x the ac frequency i.e. 100Hz or 120Hz, I'm not sure about strip lights.

The human eye can only 'see' pulsing up to about 25Hz as the eye has a low pass filter effect above that frequency. Strobe effects can easily bee seen if they are less than 25Hz.


Tom, in the US, power comes at 60 Hz. Some of our streetlamps seem to have that same frequency. I was using my HP48G under one once and I could see the flicker! I'm told that its screen refreshes at around 64 Hz or so. I think that information might even be found in this museum site somewhere...


I don't know what rate the HP48G series updates the screen. Does a 'normal' house bulb give the same result as a street light (i.e. pulsing display)? If it doesn't visibly pulse then there is possibly some other effect.

From my recollection of electronics; if a light bulb runs from 60Hz the light will pulse at 120Hz. In the UK the mains electricity is 50Hz so lights pulse at 100Hz.

Light intensity = Power = ((Voltage)^2) / Resistance

If Voltage = V x COS(freq)

Power cx= (V x COS(freq))^2

Power cx= V^2 x 1/2(1 + COS(2 x freq))

(where cx= is 'proportional to')


My office is lit by a combination of fluorescent lighting on the ceiling and daylight coming through large windows. I normally don't notice any flickering on my 48GX. Sometimes, usually late in the day when there is little daylight left and the fluorescent lights are providing most of the illumination, I notice a slight flicker. However, I have a small fluorescent light on my desk and when I examine the 48 under that light the flickering clearly is visible, especially if I view the screen at a shallow angle.

At home, where I have only incandescent lighting, I never see any flickering.

Possibly Related Threads...
Thread Author Replies Views Last Post
  HP48GX screen replacement Francisco Quiles 9 1,763 10-03-2013, 09:17 PM
Last Post: Francisco Quiles
  HP48GX Interface to a PC John W Kercheval 7 1,317 09-29-2013, 10:53 AM
Last Post: John W Kercheval
  HP48GX everything works perfectly except the 'ON' key? Bruce Larrabee 5 978 10-22-2012, 05:41 AM
Last Post: Bruce Larrabee
  HP48GX Connectivity John W Kercheval 6 1,203 05-22-2012, 06:45 AM
Last Post: Michael Lopez
  copyrom.lib on hp48gx David Griffith 0 405 04-03-2012, 07:31 PM
Last Post: David Griffith
  HP48GX : faulty Port 2 ? any way to repair it ? Antoine M. Couëtte 4 824 01-13-2012, 10:56 PM
Last Post: Antoine M. Couëtte
  hp48gx pc cable tim peterson 2 600 05-11-2011, 07:06 PM
Last Post: tim peterson
  Backed into corner on HP48GX Don Jennings 17 2,107 09-01-2010, 11:39 PM
Last Post: M. Joury
  Here's a rare HP48GX Han 5 944 03-09-2010, 10:05 PM
Last Post: Namir
  Serial no of HP48GX matti 4 725 02-15-2010, 02:54 PM
Last Post: matti

Forum Jump: