HowTo: Using a Watt Meter

Using the Hobby King X1 Watt Meter

The instructions in the package are pretty inscrutable, so here's a quick HOWTO.

Basic Idea

• This thing sits between your battery and your ESC.
• It measures voltage, amperage, and wattage.
• It has a HOLD mode that keeps the highest values.
• When it's set up, you fiddle with your props, motors, etc, and see the power requirements of various setups.
• You can send it aloft to record the flight's peak power requirements.

 Setting Up

• The unit doesn't come with any power connectors, so you need to attach your own.
• The wires labeled IN attach to the battery.  Put a male power connector here.
• The wires labeled OUT attach to the ESC.  Put a female power connector here.
• Black wire = Neutral (-)
• Blue wire = Hot (+)

Turning It On

• Plug the unit into a battery.  Whatever battery you use to fly a plane is fine (the manual says the voltage rage is 8-30V, but it seems to work fine with 2S batteries as well, as seen below).
• The display of the unit will turn on.
• If you use a 2S battery, you will see something like this:
• Voltage (U=7.93V).  Over time this will go down, as your battery discharges.
• Amperage (I=0.1A)
• Wattage (P=1.0W)

Trying It Out

• Attach a motor to your ESC.
• Plug your ESC into a receiver.  It's OK if there are servos attached.
• Attach the OUT wires to your ESC.
• Your setup should power up and work as normal.
• The power levels should go up a bit, since you're running servos and a receiver.
• Wiggle your servos.  You will see the numbers jiggle in response.

Testing a Motor

• Make sure your motor is secure, and bring the speed up.
• You will see the amperage (I=) and wattage (P=) increase.
• Bring the speed back down.
• You will see the values decrease back to the original values.
• The voltage may have gone down a bit, since you've been using some power to run these tests.

HOLD mode

• HOLD mode will measure the Peak values.
• To turn it on, click the HOLD button.
• Rev your motor and bring it back down a couple of times.
• You will see these peak values displayed. Rearranging the order a bit, they are:
• P 14.3W -- maximum power (wattage).  This is the peak power output of the battery.
• Up 7.71V -- voltage when P was at max.
• Ip 1.9A -- amperage when P was at max.
• Im 1.9A -- maximum amperage, even if it didn't correspond to P above.
  
• Um 7.84V -- the minimum voltage of the time period.
• Click HOLD again to go back to instantaneous mode.

Flight Mode

• If your plane is big enough to carry a couple of extra ounces, you can attach the meter between the battery and ESC in your plane, set HOLD mode, and find out your peak usage aloft.

Manual Calibration Mode

• If you have a good quality multimeter, you can adjust your unit's readings.
• Depress HOLD for three seconds and you will be in adjustment mode.
• Measure an unloaded power source with both the watt meter and your reference multimeter.
• Use the ADD and SUB menu items to make the two units agree.
• SAVE will of course save your calibration.