Desktop Network

The USB Sensor

Unlike laptops, desktops do not have accelerometers inside. So we connect inexpensive universal serial bus (USB) accelerometers to desktops. The USB sensors use similar to the Sudden Motion Sensors that come in many laptops. USB accelerometers connected to desktops have several advantages over laptop sensors:


  • Desktops are not usually moved around as much as laptops.
  • Desktops are usually placed on the floor or on sturdy desks, but laptops are often on people’s laps.
  • Third, the USB accelerometer is physically separated from the keyboard, so typing does not effect the sensor.
  • If the user wishes, the USB sensors can be monitored continuously, not just when the computer is in screensaver mode.
  • A USB sensor can be attached to any desktop with a USB port, not just particular laptops with accelerometers already internal to them.
  • USB sensors can be aligned to north, so we know what directions the X and Y axes actually are.

Three Directions

The sensors can measure acceleration in three directions. The easiest way to think of these directions is as the 1) up/down 2) front/back, and 3) side to side motions bobbing motions of a boat. With these three components of direction, it is possible to find the direction of the acceleration. If your laptop is not level (or horizontal), the directional acceleration may not return a zero value when it really should. This is why our software zeros each directional acceleration before it begins to monitor the sensor.

Communications and Data Transfer

Laptops connect to the Quake-Catcher Network over the Internet. Typically, when the QCN software is running, there isn’t much need to transfer the data to our headquarters. Instead, the laptop monitors the data locally for new high-energy signals and only sends a single time and a single significance measurement for strong new signals. If our server receives a bunch of these times and significance measurements all at once, then it is likely that an earthquake is happening. If the server receives only a time and significance measurement from one laptop, then the server knows the laptop was shaken by something smaller and more local (like your sister running by, or the door slamming).

Apply for a USB Sensor

If you are a science teacher at a K-12 school, please apply for a free USB sensor and accompanying QCN software. QCN has been able to purchase sensors to donate to schools in need. If you are interested in donating to the program or requesting a sensor, click here.

QCN USB Drivers

The drivers for the QCN USB sensors can be downloaded here.

USB Sensor Instructions

QCN provides instructions on how to orient your sensor, mount your sensor to the floor, and downloaded drivers for your USB sensor.


When you install the software on a desktop, you can set a permanent location through a Google Maps API. By setting the location of your laptop as precisely as you can, you will help seismologists that much more!

Orient to North

The USB sensors come with a mini compass so you can align the sensor so the X direction points toward the North Pole. (Note: magnetic North is not always the same as True North. We typically adjust for this before shipping the sensor to you. The better we know the directions of motion, the more precisely we can pinpoint the earthquake!

Timing is Everything

Every 15 minutes the Quake-Catcher software checks to see if your laptop’s clock is synchronized with the clock here at the Quake-Catcher Network. The clock here at the Quake-Catcher Network is synchronized with an atomic clock, so the whole network is always on time. Don