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HP Prime G2 currents
02-13-2020, 10:27 PM
Post: #1
HP Prime G2 currents
After a discussion about charging current, I decided to follow up and measure G2 calculator working currents. Since the battery capacity is known (2Ah), it may be helpful for estimating the battery lifetime under given circumstances.
The currents were measured on the battery terminals.

The results for the calculator after reset were:
Calculator off - 1.61mA
Calculator off, extra low power mode - 94.5uA
Calculator on, max. brightness, idle - 127.3mA *)
Calculator on, max. brightness. running program - 166.4mA *)
Calculator on, min. brightness, idle - 92.3mA *)
Calculator on, min. brightness. running program - 125.5mA *)

In addition:
For the calculator on, max. brightness, idle, the currents for different screen refresh ratios were:
Max. screen refresh ratio - 128.5mA *)
Min. screen refresh ratio - 112.8mA *)

*) Average. The current was oscillating around this value. The meter showed max/min values staying within +/-1mA from the average, but the real peak values might be higher/lower because of the meter's slow response.

Experiment details:
The currents were measured with Fluke 87V multimeter.
The extra low power mode current was measured on uA range (100.71 Ohm serial resistance), other currents on mA range (1.81 Ohm serial resistance), in HiRes mode (slower conversion). The meter serial resistances were measured; doing it like this was faster than searching for them in the meter's user manual. Call me lazy.

Darius
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02-14-2020, 06:07 AM
Post: #2
RE: HP Prime G2 currents
Hello,

Darn, this CPU does use quite a bit of current...

The reason for the ultra low power mode is the LPDDR3.
Unlike it's name suggest, it actually does use quite a bit of power, even in IDLE mode... hence the 1.6mA in off mode. Thus the reason for the "coma mode" which turns off the RAM...
That ram module uses a lot more power than the G1 ram (it is also much larger...)...

I was also surprised by the power consumed by the screen refresh... as you can see, going from 55hz to 115hz uses around 16mA. We can then deduce that it uses around 1.6mA per 10hz of screen refresh. This is a fair chunk of the power use.

The flash uses around 15mA normally (it gets turned off in off mode with the off code being copied in ram)...

I honestly do not know where the rest of the power goes.
G2 has a lot of tricks in play to minimize power use, but it is still higher than I would have liked it...
On the other hand, it is amazingly fast compared with G1, especially in applications like the advanced grapher.

Cyrille

Although I work for the HP calculator group, the views and opinions I post here are my own. I do not speak for HP.
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02-14-2020, 02:13 PM
Post: #3
RE: HP Prime G2 currents
(02-13-2020 10:27 PM)DrDarius Wrote:  After a discussion about charging current, I decided to follow up and measure G2 calculator working currents. Since the battery capacity is known (2Ah), it may be helpful for estimating the battery lifetime under given circumstances.
The currents were measured on the battery terminals.

The results for the calculator after reset were:
Calculator off - 1.61mA
Calculator off, extra low power mode - 94.5uA
Calculator on, max. brightness, idle - 127.3mA *)
Calculator on, max. brightness. running program - 166.4mA *)
Calculator on, min. brightness, idle - 92.3mA *)
Calculator on, min. brightness. running program - 125.5mA *)

In addition:
For the calculator on, max. brightness, idle, the currents for different screen refresh ratios were:
Max. screen refresh ratio - 128.5mA *)
Min. screen refresh ratio - 112.8mA *)

*) Average. The current was oscillating around this value. The meter showed max/min values staying within +/-1mA from the average, but the real peak values might be higher/lower because of the meter's slow response.

Experiment details:
The currents were measured with Fluke 87V multimeter.
The extra low power mode current was measured on uA range (100.71 Ohm serial resistance), other currents on mA range (1.81 Ohm serial resistance), in HiRes mode (slower conversion). The meter serial resistances were measured; doing it like this was faster than searching for them in the meter's user manual. Call me lazy.

Darius

Those values look slightly (5%-15%) higher than the G1, which makes sense.
http://www.hp-prime.de/files/composite_f...report.pdf

The "ultra low power mode" was not included on the test.

My website: erwin.ried.cl
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02-17-2020, 06:11 AM
Post: #4
RE: HP Prime G2 currents
Hello,

G2 has a slightly higher power use than G1 when compared side by side...
BUT, G2 computes faster, so it should spend more time in IDLE mode, which should help...
Also, G2 coma mode is way more efficient than G1...
And, to cap it off, G2 has a higher capacity battery...

All in all, G2 should last longer under normal use...

I have a G2 in my workshop which is used every week or so, and I have not had to recharge it in over 6 months... Which is darn impressive.
Yesterday I picked up a G2 that I had probably not touched in over a year, and it was still working...

Cyrille

Although I work for the HP calculator group, the views and opinions I post here are my own. I do not speak for HP.
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