TECH  BULLETIN

Units Affected:  RockeTiltometer^TM 2        Date Issued:      02-29-12

                                                                    Date Updated: 03-01-12

Issue:  Gyro Drift at Arming

Closing the Ignition Battery Switch and Arming Switch terminals (T1, Pins 7&8 and 3&4) in the normal arming sequence can cause a shift in the output signals of the gyros. This is due to the introduction of a slight difference in the supply voltage to the components on the order of 0.001 to 0.003 volts which results in a single bit toggling of the 12-bit A/D converter.

The Current Angle therefore drifts upward from nominal for approximately 30 seconds, and then settles back down to nominal over another period of approximately 30 seconds while the firmware makes an adjustment.

The amount of drift varies from 1 degree to as much as 10 degrees, but always returns to nominal.

 Effect on Usability:

Minimal.

The effect is transient - as long as the user allows at least 75 seconds after activating the Arming Switch before launching the rocket, the system will react to and take care of the voltage shift.