4 ms·

Why are you referring to the units of mA for "power", as opposed to current draw? The power consumed would be measured in watts or milliwatts.

by chatman 11y ago

robzyb 11y ago
The Raspberry Pi runs on a fixed 5 volts. At a fixed voltage power will scale linearly with current.
- langarto 11y ago
  That's a poor excuse for not using the correct terminology or the correct units.
  - geerlingguy 11y ago
    I use Watts on the page where I aggregate my results[1], but since most USB-related projects measure mA (and most battery ratings use mAh), I use the same convention as a default, since 5V can be assumed in all cases. [1] https://github.com/geerlingguy/raspberry-pi-dramble/wiki/Power-Consumption https://github.com/geerlingguy/raspberry-pi-dramble/wiki/Pow...
  - theGimp 11y ago
    I have pretty much never seen a component specify wattage. They always specify the voltage and current draw. Voltage and current are easy to measure with a pair of multimeters, so it's more useful to have those numbers than wattage.
  - robzyb 11y ago
    It wasn't intended to be an excuse for not using "correct" terminology or units. The reason that these terminology and units were used by OP was because at a fixed voltage it is common for engineers to think about current instead of watts... even when their aiming to reduce power. I'm not sure of the exact reason for this, but I suspect that it's because: a) Measuring current is a more fundamental function of instruments. Quite a lot don't even measure power. So talking about current instead of power, even when you're aim is to reduce power, makes for a smoother process from a practical sense. b) Batteries are usually measured in mAh. At lower power/currents you're usually using a linear regulator and therefore dividing mAh by mA is a very important measure. So you often keep everything in mA.
weland 11y ago
When studying power consumption for this type of devices, it's extremely common to measure the current being drawn, rather than to put out values in watts. For one thing, it's the current that you usually measure in these cases anyway. For the other, power consumption in watts is not what you generally want to know when you design a battery-powered circuit. And, last but not least, it's more useful to have a figure in (m)A than (m)W when batteries are rated in mAh. It's not correct terminology, mind you, but then neither is that of energy in your energy bill, so I guess this can be forgiven.
- chatman 11y ago
  But the mA units were used in a table whose column heading said "Power saved". No matter what is "extremely common to measure", but it cannot be put in a wrong heading.

Why are you referring to the units of mA for "power", as opposed to current draw? The power consumed would be measured in watts or milliwatts.

by chatman 11y ago

Why are you referring to the units of mA for "power", as opposed to current draw? The power consumed would be measured in watts or milliwatts.

robzyb 11y ago

The Raspberry Pi runs on a fixed 5 volts. At a fixed voltage power will scale linearly with current.

langarto 11y ago
That's a poor excuse for not using the correct terminology or the correct units.
- geerlingguy 11y ago
  I use Watts on the page where I aggregate my results[1], but since most USB-related projects measure mA (and most battery ratings use mAh), I use the same convention as a default, since 5V can be assumed in all cases. [1] https://github.com/geerlingguy/raspberry-pi-dramble/wiki/Power-Consumption https://github.com/geerlingguy/raspberry-pi-dramble/wiki/Pow...
- theGimp 11y ago
  I have pretty much never seen a component specify wattage. They always specify the voltage and current draw. Voltage and current are easy to measure with a pair of multimeters, so it's more useful to have those numbers than wattage.
- robzyb 11y ago
  It wasn't intended to be an excuse for not using "correct" terminology or units. The reason that these terminology and units were used by OP was because at a fixed voltage it is common for engineers to think about current instead of watts... even when their aiming to reduce power. I'm not sure of the exact reason for this, but I suspect that it's because: a) Measuring current is a more fundamental function of instruments. Quite a lot don't even measure power. So talking about current instead of power, even when you're aim is to reduce power, makes for a smoother process from a practical sense. b) Batteries are usually measured in mAh. At lower power/currents you're usually using a linear regulator and therefore dividing mAh by mA is a very important measure. So you often keep everything in mA.

weland 11y ago

When studying power consumption for this type of devices, it's extremely common to measure the current being drawn, rather than to put out values in watts. For one thing, it's the current that you usually measure in these cases anyway. For the other, power consumption in watts is not what you generally want to know when you design a battery-powered circuit. And, last but not least, it's more useful to have a figure in (m)A than (m)W when batteries are rated in mAh. It's not correct terminology, mind you, but then neither is that of energy in your energy bill, so I guess this can be forgiven.

chatman 11y ago
But the mA units were used in a table whose column heading said "Power saved". No matter what is "extremely common to measure", but it cannot be put in a wrong heading.