Configuration
Four single hot-films will be deployed along with sonic anemometers on the t0 tower at heights of 0.5, 1.0, 2.0, and 4.0m. They will be vertically oriented (measuring horizontal speed), mounted on probe supports attached to the sonic anemometer array. Two bridge enclosures will each hold 3 bridges, but only two bridges in each enclosure will be used (this allows a bridge to be replaced, if needed, by another already in the enclosure). A LabJack T7 housed inside the t0t(?) DSM will be used as an A/D to digitize the 4 signals from each of the hot films at approximately 2,000 sps. Code is being written to archive these data in a nidas-compatible format synchronized to the GPS PPS timing signal along with 1-s averages to allow a quick monitoring of the data. Ordinary coax cables with BNC connectors are used both between the probe support-to-bridge and bridge-to-LabJack.
Operation
Voltages will be monitored by looking at the 1-s average signals. The normal range is about 1.5-4.0V. If a probe is broken, the signal goes to about 4V (check!). If a probe has to be replaced:
- locate the container for the probe that has broken (we will need to maintain a list of which probe is in which position)
- disconnect power to the appropriate bridge enclosure
- open the empty probe container
- loosen the end of the probe support
- carefully (linked two-hand method) pull the broken probe out
- carefully put the broken probe in the container end cap
- carefully screw the container cover onto the end cap
- carefully remove the container cover from the new probe
- carefully put the new probe in the end of the probe support and ensure that it is connected and rotated to have the sensor vertical
- tighten the end of the probe support
- open the bridge enclosure
- open the specific bridge
- referring to the sheets below for the specific new probe (SF1–9), set the DIP switches
- close the bridge
- close the bridge enclosure
- power on the bridge enclosure
We only have 7 probes for the 4 positions for the entire experiment, so we want to be very careful to avoid accidental breakage!!