The data acquisition console takes the analog signals from the preamplifiers and turns them into timing data which can be interpreted into useful information.  There are two families of Hood Technology Corporation’s BVM data acquisition consoles.  The first is the model 8030, mounted in a self-contained 19” instrumentation rack.  The newly developed model 4016C has integrated preamplifiers, a much smaller form factor and all solid state components.  Versions of this system have been used in flight testing.  Table 1 highlights the major differences between the two models.

Table 1:  Comparison of data console models 8030 and 4016C.

  Model 8030 Model 4016C1
Timing Resolution 80MHz, 12.5ns ~ 4um at 340m/s rim speed 40MHz, 25ns ~8um at 340m/s rim speed
Data Streaming ~1.5Mblades/sec ~0.25Mblades/sec
Maximum Channel Count 30 16
Outer Dimensions 650mmX900mmX1100mm 222mmX465mmX199mm
Weight ~130kg ~10kg
Virtual Oscilloscope Yes, up to 1.2Msamp/sec Fast refresh rate Yes, up to 0.5Msamp/sec ~ 1 second refresh rate
Preamplifiers Separate Integrated
Power Consumption 185 to 550W 60 to 120W
Power Requirement 110-240VAC 24-35VDC
Thermoelectric cooling of laser diodes No Yes

1. BVM Model 8030

A photograph of a 30-channel version of BVM model 8030 is shown in Figure 1.  This system hosts 1 to 10 BVSI modules, each supporting a Hood Tech preamp and 3 channels of sensor data.

Figure 1:  Model 8030 data acquisition console.  Standard 19 inch rack is soft-mounted.  Console is on casters and has removable front and back lids for shipping and safe storage.

The Blade Vibration Sensor Interface (BVSI) unit, developed by Hood Technology Corporation ( Figure 2 ), conditions analog blade passage signals and converts them to a digital signal, which is precisely timed. The BVSI performs the following functions:

  • It provides power to Hood Technology's sensors, filters, repeaters and conditioning electronics.
  • It allows one to determine blade passage on a repeatable feature of the analog pulses generated by the sensors.
  • It provides a logic pulse indicating Time-Of-Arrival and an additional pulse indicative of pulse magnitude (i.e. tip clearance) which are timed by the National Instruments Timer Card.
  • It communicates with Hood Technology’s Acquire Blade Data software, allowing the user to change BVSI settings (see in Table 2) via a graphical user interface.

Figure 2:  Blade Vibration Sensor Interface (BVSI) conditions the analog blade passage signals and converts them into precisely timed digital signals.

Table 2: BVSI Parameters and their associated ranges or possible values.

Parameter Min Value Max Value
Gain -25 25
High Pass Filter Cutoff 0 Hz 3397 Hz
Low Pass Filter Cutoff 23 kHz 1496 kHz
Offset -7 V +7 V
Arm level 0.055 V 4.995 V
Trigger Edge Rising/Falling N/A
Trigger Level 0 % 90 % of max value attained
Hold Off 0.2 µs 4984 µs
Decay Rate Slow/fast N/A

2. BVM Model 4016C

Blade vibration monitor model 4016C was developed in 2008/2009.  The cabling diagram, shown in Figure 3, is somewhat different than model 8030.  The 4016C has all the features of the BVSI, BV-IND, and BV-OP integrated in a single box.  In use, it would be located near the sensors.  Rather than run cables with power and signal to the acquisition console, only an Ethernet cable is required to transmit data to a ‘ground station’, which could simply be a laptop computer running Acquire Blade Data.  The figure also shows a flight-test implementation with a telemetry link.  The first use of this system was in flight test of a military aircraft.

Figure 3:  The cabling diagram of the BVM model 4016C is somewhat different than Model 8030, because the BVSI and preamplifier are integrated into one box that is located near the sensors.  Data are streamed to disk, via UDP or TCP/IP.  The “ground station” can be simply a laptop connected with an Ethernet cable.

Figure 4:  External dimensions of model 4016C.