Newsgroups: comp.sys.hp48

jlysag4@hubcap.clemson.edu [james joseph lysaght] writes:

> Does anybody know the trade off between turning the calc on and off
> repeatedly as opposed to leaving it on for a while. Specifically,
> does the calc use much power turning on?  Does the calulator use
> much power when on, but sitting idle?  Which power consumption rate
> is greater?

Doug Cannon posted these measurements last November:

Current |       Operation                |  Other
 ( mA ) |                                |
---------------------------------------------------------------
0.016   | HP OFF                         | probably not reliable
2.22    | idle                           |
7.0     | "normal" program execution     | ( most programs )
7.0     | Stack manipulations            |
6.62    | BEEP                           | 600 Hz
8.84    | BEEP                           | 8000 Hz
8.85    | BEEP                           | 10000 and above
< 4.6   | Clock on in status line        | fluctuates (2.22 - 4.6 mA)
3.6     | Command line input             | idle
6.8     | Plotter                        | sin(x)
< 3.9   | Edit mode                      | ( 3.6 - 3.9 )
7.2     | Edit mode when checking syntax | or moving cursor

Although Doug didn't measure it, it's a fair guess that turning on and
off the HP 48 takes about as much juice as running a regular program
(that's all it's doing!).  Depending on how many libraries and cards
you have in your 48, the power-on and power-off can take from almost
no time to a second or so.

> If a student is sitting in a class where the calculator will be used
> several times but with lengthy gaps in between, would the student be
> better to turn the calcualtor off, leave it sit there turned on till
> it shuts itself off, leave it on, and hit a key every few minutes to
> prevent it from shutting itself off?  I am inclined to think that
> turning it off is the optimum choice.  Others seem to think turning
> it on each time burns more power than leaving it on and idle and
> they think leaving it on for a few minutes (not too long) would be
> the optimum choice.  So, who wants to tackle this one?

I agree with you:  Turn it off, every time!  Since turning it off and
back on takes as much power as pressing a key (or running a program)
for a second or so, but idle mode takes 1/3rd that much power, you'll
do best to turn it off after just a few seconds of non-use.

The *worst* choice is periodically pressing a key to keep it on, which
reminds me of the way they give you something to squeeze every 10
seconds when you're donating blood, to keep it draining...

Although "coma mode" (ON-SPC) uses even less power than OFF, I don't
suggest it, because it causes Memory Clear just when you don't want it
to.

If you're really concerned about battery life, never use the CLK mode,
which causes a power hiccup (albeit brief) every second, even during
running programs.  And NEVER use I/R for printing, which is like using
the HP 48 as a bulky penlight.

-Joseph K. Horn-   -Peripheral Vision, Ltd.-
"Power corrupts, but too little power corrupts absolutely everything."
From: akcs.joehorn@hpcvbbs.cv.hp.com (Joseph K. Horn)
Date: Fri, 31 Jul 1992 07:40:11 GMT
Subject: Re: Tricks with pointers
Message-ID: <2a78e8d2.1492.2comp.sys.hp48.1@hpcvbbs.cv.hp.com>