What is electric bike Pedal Assist ? 

ebike pedal assist or called PAS

Pedal Assist automatically turns on the motor when you pedal. With pedal assist you do not need to use a throttle to control the motor. 

There are two types of Pedal Assist: Cadence Sensor Type which measures IF you are pedaling and a Torque Sensor Type which measures HOW HARD you are pedaling. The Super73 S-Series sold in the United States with thumb throttles, as well as the Super73-SG (Global) has a cadence sensor. The Super73-SG1, sold outside North America, and doesn't come with a throttle, has a torque sensor. 

1. Cadence Sensors
The basic cadence sensor uses a magnet on the crank, it turns the motor ON when you start pedaling and turns it OFF when you stop pedaling. It works more or less like a switch. You control the boost level and speed by adjusting the assist mode manually up and down. 

The advantage is that it's an inexpensive way to get some sort of pedal assist onto the bike, but the disadvantage is that the pedal assistance can feel jerky, laggy and counterintuitive. If you want to pedal faster than the motor is spinning, the motor will actively work against your efforts. The Super 73 has a cadence sensor as it is most often used with the throttle only.


2. Torque Sensors
The torque sensor is a totally different technology that uses a precision strain gauge. It measures your actual force on the pedal, sampling at 1,000 times per second over the entire pedal stroke. 

The harder you pedal, the more power it gives to the motor. If you pedal lighter, less power goes to the motor. It makes this adjustment in real time so it is technically amplifying your every input. It feels like you're bionic. 

Most all higher-end e-bikes use torque sensors and in some countries, cadence-only sensors are not allowed to be sold. The disadvantage is the cost is significantly higher to implement this technology as the precision component is relatively more expensive.