FAQ: MicroVib II - Troubleshooting Sensors,
Cables & Channels
Use the tips below to troubleshoot
MicroVib II sensors, cables,
and mux channels.
To troubleshoot MicroVib II
My MicroVib II Isn't Receiving Signals From
My Sensor(s) - What Might Be Causing This?
MicroVib II Sensor, Cable and Signal Mux problems generally fall
into one of the following categories. These are listed in order of likelyhood to
be the cause of your connection problem:
- The desired Sensor Cable is not
plugged into the currently selected Signal Mux channel.
- The Mux Unit is not being
recognized by the MicroVib II.
- The MicroVib II Input Settings
may be incorrect for the desired Sensor.
- The MicroVib II History File might be
- There may be a hardware fault in the
MicroVib II, Signal Mux, Cable or Sensor.
How Can I Make Sure My Sensor Cable Is
Plugged Into The Correct Channel?
- 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).
- 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.
- Remember that Vibration channels are
always identified Numerically (1, 2, 3, 4) and Tach channels are
identified Alphabetically (A, B, C, D).
- Take care to insure that the
Accelerometer and Tach cables are not swapped.
How Can I Make Sure My Signal Mux Is
Recognized By The MicroVib II?
- 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.
- 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:
- To check peripheral type after initial
startup, press MODE, CONTROL PANEL, SYSTEM PARAMS. On the
System Parameters screen look for the line indicating: Connect:
What If I Have No Tach Signal?
- If using a signal mux unit, make sure your
tach cable is connected to the currently selected channel.
- With the aircraft shut down and the DSS
1015 Photo-Tach powered up, rotate 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 and less than 30 inches 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
What If My Tach Signal Varies?
- 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
- 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.
What If I Have A Hardware Fault?
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
- 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
- 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
- If you suspect a bad cable or connector,
compare continuity (beep test) of your cable against cable pinout
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