Inertial Navigation
   IMU and INS
   Your Application
   Unaided Position Estimate
  
Relative Attitude Determination

Orientation Sensors

   AHRS
   Inclinometer   


Sensors
   Magnetometer
   Accelerometer
   Gyroscope
   GPS

Calibration
   Intro
   Purpose
   Sensor Model
   Accelerometer
   Magnetometer
   Gyroscope
   Thermal

Using the VN-100
   Embedded Library Example

What is the difference between the VN-100 and the VN-100T?

A common problem for many measurement systems is that the measurements vary both with the variable they are designed to measure and to some degree with temperature. The MEMS sensors utilized in the VN-100 are also sensitive to temperature. The degree of sensitivity varies significantly across the various sensor types (accelerometer, magnetometer or gyro) and also with which parameter (sensitivity, bias or misalignment). Due to the sensitivity of the individual MEMS sensors, the VN-100's output will also in turn be sensitive to temperature. The VN-100 is subjected to a full characterization of sensor biases, misalignments and sensitivities at room temperature.  This allows for very good performance when the VN-100 is operating near the temperature it was calibrated at.

A VN-100T module is subjected to a significantly more demanding test and characterization. VectorNav utilizes computer controlled environmental chambers, running off liquid nitrogen supply systems, to create an environment that subjects the VN-100T to temperatures ranging from -40 to 85 degrees Centigrade. This in turn allows us to fit polynomial curves to the various sensor parameters variation with temperature. In order to accurately capture the variation with temperature 3rdorder polynomials are required. The VN-100T utilizes an on-board temperature sensor to measure the temperature and then it corrects its calibration parameters by an amount that depends on the temperature. This extensive calibration is very time demanding and consumes large amounts of liquid nitrogen, but it ensures that the VN-100T's performance is valid at any temperature in the -40 to 85 C temperature range.

The room temperature is defined at 25 degrees Celsius; however, the VN-100's temperature during room temperature calibration can vary by a few degrees Centigrade. So one might ask:  for what temperature range is the VN-100 suitable?

Our testing has shown that typically the orientation accuracy of the VN-100 varies by approximately 0.5 degrees in the 5 C from room temperature. Put simply this means that the VN-100 will start accruing errors if you use it in an environment that is significantly (more than 5 degrees C) warmer or cooler than the indoor environment.  It is important to note that temperature experienced by the VN-100 can be significantly higher in tightly packaged electronics!

If absolute accuracy is not very important in your application and the temperature environment is fairly well understood to be near room temperature than we recommend you develop with the VN-100.

If you do expect to operate away from room temperature, or in varying or uncertain temperature ranges you should be planning on utilizing the VN-100T. If you are working on an application that requires the best possible performance we highly recommend the VN-100T.

Since the only operational difference between VN-100 and VN-100T is the temperature compensation it is not uncommon for our customers to start development with the VN-100.