Hello, I work at present on a project electric moped (bike with electric engine + battery. The moped will possess an engine brushless of 750W as well as a battery lithium. My project personal is to post the immediate consumption by means of a display 7 segments 2 Digits under Arduino and all this in ampere. I would need your help, I do not know how to take myself there my professor told me that I had to connect the whole on the thread which goes of the engine to the battery. Thank you for your answers. 
Presumably you know the battery voltage so you just need to measure the current (amps) to see how much power is being used.
I presume the motor will draw a very high current so you probably need some form of clip-on DC current sensor.
...R
Perhaps one of these. It measures volts, amps, watts and WattHours used
http://www.ebay.co.uk/itm/100A-DC-Digital-Power-Energy-Meter-Monitor-Module-Ammeter-Voltmeter-with-Shunt/282203495253?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D2%26asc%3D20140122125356%26meid%3Da4ffbbf6d71a4c3ebf8935454f560511%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D112170345926
Thank you for your answers but, jackrae, I have to show the consumption on an arduino screen. Robin2 you have an idea of the type of sensor whom I should use and which would be compatible with the arduino card. Can I cross by the arduino shield card with a sensor with effect Hall ? Or a sensor like this: Capteur de courant ASM50 Talema - Courant | GO TRONIC
Awaiting your answers.
That device is NOT suitable as it is for AC only.
You need something similar that is designed for DC. I suspect Googling Arduino DC current sensor might help. I have never used one of the things myself.
...R
This might be a language thing, but in your thread title you talk of energy, while in the body you talk of immediate consumption ... in ampere.
Now, current at a fixed voltage is an indicator of power not energy, which is the integral of power over time. So if you do mean energy not power (as indicated by current), then you need some way to record the the power (or at least the current) usage over time and add them all up.
But I suspect you may just be using the word energy loosely?
then how about one of these
Edit : Not enough range for a 750W motor but there are many similar units out there if you simply google something like "DC hall current sensor"
If the OP wants to measure power being consumed, then as the project is using some kind
of Lithium battery, the battery voltage also needs to be measured, as if its a LIPO of some type, which are the most common for this type of application, the voltage can vary from 4.2 V down to 3 volts per cell.
Would help if the OP could actually clarify what they are trying to measure.
Something like this might work up to 100a.
And a resistor divider for your voltage as mauried mentioned.
Thanks to all of your answers. Manor_royal to excuse I but I badly expressed myself I actually have to show the power in ampere. Finally I am going to leave on a sensor to effect Hall, I am going to follow your advice, at the moment the moped is only at the stage of frame.
PatrickFox:
I actually have to show the power in ampere.
Except power is the product of volts and amps, so if you really want power, you will need to measure the voltage too as mauried says, unless you can assume it's constant.
PatrickFox:
I actually have to show the power in ampere.
That is perfectly reasonable. But you must understand that an Ampere is a measure of current, not power.The unit for power is the Watt.
...R
I think you mean "I actually have to show the power energy in ampere hour."
To monitor the energy (Ah) consumed, just need to take readings of current along with elapsed time since previous reading. The Ah value is totalized, that is it accumulates after each reading (as long as current >0).
dlloyd:
I think you mean "I actually have to show thepowerenergy in ampere hour."
It makes sense to me that someone would simply want to know how many amps are flowing at any moment.
It does not tell you the accumulated amount of energy that has been used but it is a reasonable proxy for the rate at which energy is being consumed.
...R
It makes sense to me that someone would simply want to know how many amps are flowing at any moment.
Need to take readings of both amps and time with sample rate as high as possible. For each reading (or averaged batch of readings) calculate the Ah and add it to an Ah counter (totalizer).
When thinking of what remaining charge is left in a battery, the Ah count would be the amount of energy consumed from the battery.
Drawing 100A from the battery doesn't say anything as to how much Ah energy was consumed.
Drawing 100A for 100µs gives you everything needed to calculate Ah energy consumed.
The running total of Ah energy is what's important.
dlloyd:
Need to take readings of both amps and time with sample rate as high as possible. For each reading (or averaged batch of readings) calculate the Ah and add it to an Ah counter (totalizer).When thinking of what remaining charge is left in a battery, the Ah count would be the amount of energy consumed from the battery.
Agreed. But we have no information to suggest the OP is interested in that.
...R
dlloyd:
I think you mean "I actually have to show thepowerenergy in ampere hour."
Methinks you mean "Current" "Energy" is a measure of Joules or Watt-Seconds and is only relevant if you also consider the voltage.
jackrae:
I think you mean "I actually have to show the power energy in ampere hour."
Methinks you mean "Current" "Energy" is a measure of Joules or Watt-Seconds and is only relevant if you also consider the voltage.
Methinks that is not quite right either.
Current is measured in Amperes. Ampere-hours are a different thing,
...R
There's always the title of this thread, or Google "ampere hour", but it would be good to hear from the OP.
Be careful, as there are safety concerns.