Being able to measure electrical values is a great way to confirm and check over your power system. This may be essential if you are building an RC model where you have chosen the power system gear. Keep in mind all electrical components worst enemy is heat. Making certain your motor, ESC, and LiPo batteries are all operating with in there intended range is required.
There are two common ways to mearsure Electrical Characteristics for RC purposes. This includes the tools known as a Digital Multimeter or a Data Logger. Each tool serves a different purpose at different times and one may be much better suited depending on what is required.
Multimeters – Measuring Electricity
Many are familiar with the common household Multimeter. It’s main feature is its 
ability to measure basic electrical functions quickly and accurately. Nearly every multimeter out there has the ability to measure voltage for all of our applications. However when it comes to measuring resistance and current they are usually quite limited. Most multimeters do not have the sensitivity to measure low resistance values. Most motors in use for RC have a resistance value of less than 0.1 ohms. Some all the way down to 0.002 ohms. In order to accurately read these values, your multimeter would have to be quite sensitive.
When measuring current with a multimeter, most multimeters are limited to 10A. This may not be helpful to us as more than 90% of the setups out there will draw more than 10A of current. Other multimeters can only read several hundred mA as a max.
Data Logger – Measuring Electricity
A data logger is a device used to log specified parameters. These perameters can be reviewed later. The data logger is plugged in to your RC model and can then go along for the run. During the run the parameters selected for logging will be stored to memory. This is excellent for not only seeing the peak values. The entire run is stored in order to determine peaks and constants.
An example of a graph output for an entire run from the unit shown above is found below:
From this data I know exactly how much capacity was drawn from my LiPo battery pack, peak current, voltage drop under full load ect.
In addition to this, other parameters can be logged with add on units. It’s a great tool for the world of Electric Radio Control modeling in terms of measuring electrical figures, however it can also be used for measuring location, speed, altitude, temperatures ect.
Other Meters are available similar to the data logger. If the unit only measures peaks keep this in mind. Often times the peak current is only pulled in a short burst. What is more critical is the maximum current pulled or drawn during a longer duration of time.