FAQ: MicroVib II - Troubleshooting Sensors, Cables & Channels

Use the tips below to troubleshoot MicroVib II sensors, cables, and mux channels.

To troubleshoot MicroVib II settings, click here.

MicroVib II Sensor, Cable and Signal Mux problems generally fall into one of the following categories. These are listed in order of likelihood to be the cause of your connection problem:

1. The desired Sensor Cable is not plugged into the currently selected Signal Mux channel.
2. The Mux Unit is not being recognized by the MicroVib II.
3. The MicroVib II Input Settings may be incorrect for the desired Sensor.
4. The MicroVib II History File might be corrupted.
5. There may be a hardware fault in the MicroVib II, Signal Mux, Cable or Sensor.

1. Check the currently selected Task name and make sure it agrees with step(s) you are performing in your DSS Application Note Procedure. For instance, if you are performing Tail Rotor Balancing, your currently selected task will be something like TR BAL (tail rotor balance).
2. Observe the channel designation underneath the Task Name and make sure that it matches the sensor and cable installation on your aircraft. For example, a channel designation of CH:4D means the Accelerometer cable should be connected to Channel 4 and the Tach cable should be connected to Channel D.
3. Remember that Vibration channels are always identified Numerically (1, 2, 3, 4) and Tach channels are identified Alphabetically (A, B, C, D).
4. Take care to insure that the Accelerometer and Tach cables are not swapped.

1. Connect the MicroVib II to the Signal Mux and then power up the MicroVib II unit. While Hot Plugging the MicroVib II and Signal Mux will not cause electrical damage to either unit, doing so will interfere with the Signal Mux being identified properly. If the MicroVib II cannot identify the Signal Mux unit, the default signal path read by the MicroVib II will be from Channels 1A.
2. Upon initial startup, the MicroVib II will display what peripheral it has connected with for two seconds. Look at the bottom of the startup screen for the following indication:   Connect: <peripheral type>.
3. To check peripheral type after initial startup, press MODE, CONTROL PANEL, SYSTEM PARAMS. On the System Parameters screen look for the line indicating:   Connect: <peripheral type>.

• Connect your Signal Simulator to the MicroVib II and make sure it can display a valid Tach Signal. For instructions on performing a functional check of the MicroVib II, click here.
• If using a signal mux unit, make sure your tach cable is connected to the currently selected channel.
• Check the DSS 1015 Photo-tach lens for dirt, grease or other foreign material blocking the beam.
• Check to see if there is moisture/condensation inside the Photo-tach lens.
• With the Photo-tach powered up, make sure the red transmit light appears behind the lens.
• With the aircraft shut down and the Photo-tach powered up, turn the rotor so the Reflective tape passes through the Photo-tach beam. You should see the red pilot light on the back of the Photo-Tach illuminate when the tape is in the beam.
• Check your distance from Photo-Tach to Reflective tape. The DSS 1015 Photo-Tach generally requires a distance of greater than 4 inches (10.16cm) and less than 30 inches (76.2cm)to the Reflective tape.
• Make sure you are using genuine DSS supplied reflective tape P/N 1017 or P/N 1254. Using other brands of reflective tape will significantly reduce the range described above.

• Make sure you only have a single piece of Reflective tape mounted on your rotor.
• Check your beam to tape angle. The ideal angle between the Photo-tach beam and Reflective tape is 45 to 60 degrees. If you are forced to use a beam to tape angle near 90 degrees (perpendicular), then the entire circumference of the rotor seen by the Photo-Tach must be non-reflective so as to not create false reflections.
• Make sure the alignment between Photo-Tach beam and Reflective tape is properly maintained as the machine is operated.
• Make sure your Reflective tape is wide enough for its velocity. The DSS 1015 Photo-Tach beam must "see" the Reflective tape for a minimum of 300us. If you have a good tach reading at lower rotor speeds and the reading degrades or disappears once you reach a higher speed, then your Reflective tape must be widened or its radius made smaller.

• Connect your Signal Simulator to the MicroVib II and make sure it can display a valid Tach Signal. For instructions on performing a functional check of the MicroVib II, click here.
• If using a signal mux unit, make sure your tach cable is connected to the currently selected channel.
• Check to make sure the rotor is equipped with only one, single interrupter.
• Check that the Mag Pickup to Interrupter gap is set to .050" (1.27mm).
• Use a DVM to check resistance between Mag Pickup pins A & B. You should see 1000 ohms +/-10%

Look for obvious damage to cables and connectors. Be particularly careful to note burn marks, cuts and pinches in cable jacketing. You can substitute sensors and/or cables to isolate many hardware faults. Below are several advanced techniques that may also help.

• To test the MicroVib II to Signal Mux communications path, connect the Signal Mux and then start the MicroVib II. Check the System Parameters screen for Signal Mux identification. If the MicroVib II identifies the Signal Mux, then the communications path is working properly.
• To test for a failed Signal Mux unit, substitute the DSS 1131 "Y" cable for the Signal Mux and determine if the substitution changes the behavior.
• To test for a failed Signal Mux channel, select a Task which uses a different channel and move your cables to the new channels and determine if the channel change results in different behavior.
• If you suspect a bad cable or connector, compare continuity (beep test) of your cable against cable pinout information here.

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