Operation Manual

Joule GPS User Guide page 21
TIP: The accuracy of any power meter is dependant on many variables, especially temperature. Fluxuations in temperature
affect the internal strain gauges, which affects the reported torque value (power is calculated from torque). The PowerTap
Auto Zero feature continually adjusts the calibration of your device, compensating, in real time, for environmental factors like
temperature, assuring that you have the most accurate power data throughout your ride.
Power Sensor
Activate Sensor
Start Pairing
Name
Power2
Sensor ID
2484
Circumference, mm
2096
Auto Zero
On/Off
Delete Sensor
Manual Zero
Back to Bike
9:34A
CHAPTER 4: SENSORS
CALIBRATION, AUTO and MANUAL ZERO
There are many environmental factors that can affect the accuracy of a power meter. Temperature, humidity, and circuit
resistance are part of the measurement, but none of them remain constant while riding. A power meter must account for those
changes to remain accurate. Auto-zero recalibrates the power meter over and over during a ride to keep the measurements
from drifting. Use the Auto or Manual Zero options in the Power Sensor screen to calibrate your power meter, assuring you are
getting the most accurate power data all time.
Power2
Manual Zero
Torque RAW
<Value>
Torque Offset
<Value>
Firmware Version
45
Back to Sensor
9:34A
Auto Zero
Manual Zero
On or Off. Typically, always On. The Auto Zero
function follows the same steps outlined for
Manual Zero but does it continually during the
ride, whenever the bike is coasting for 4 or
more seconds. If your bike is a fixed-geared
or track bicycle you may consider turning
Auto Zero off.
Calibrating or “zeroing the torque” refers to the
process of resetting the Torque Offset value of
the physical torque tube (where the internal
strain guages actually measure wheel torque).
1) Make sure the power meter is awake and
communicating with the Joule. Make sure
the bike is sitting still, no feet on pedals, no
tension in chain.
2) Select Manual Zero on Power Sensor screen.
The Calbration screen will appear. Torque
RAW should be 0. The last saved Torque
Offset is displayed. The value is typically
500-524 in-lbs.
3) Select Manual Zero on Calibration Screen.
The Torque Offset value will update with the
torque tube calibration value, given the
current environmental conditions.