Here is the Hydra DAU.  It has two data input terminals at the left on the front panel, and another twenty sets of input and output terminals that have been wired to a connector on the top of the unit.  It has an LED message panel on the right (the large black space), and measurements are displayed there normally - but not when you take a reading using a computer program.

Turn the Hydra on.  That's not a facetious statement.  Depress the green button at the lower right of the instrument's front panel.  And be sure it's plugged in.  The Hydra will go through a start-up sequence (green LEDs will flash on the front panel) and it will come up in the mode it was last in before being turned off.

The Hydra may come up in a monitor mode.  That means it takes repetitive measurements - which might be voltage, temperature, etc. on a particular channel - and it will start that operation.  If it comes up in monitor mode - and you will know that by it's efforts to take measurements repetitively - depress the white MON key in the lower right corner of the front control panel.  That toggles the Hydra out of the monitor mode.

       If you want to use the Hydra from within a program - in C, Visual Basic, or any other programming environment - there are several items to take care of before the Hydra can communicate with the computer.  There are two things to address.

The Hydra must be set to communicate with the computer.  To set the Hydra, do the following:
 
• Turn the Hydra on.
• If it comes up in Monitor mode, turn the monitor mode off.
• Select COMM by pressing Shift and List sequentially - not simultaneously!
• Cycle through the communication settings (baud rate) to get IEEE.  Press Enter.
• Next, you need to set the address to 3 by cycling through possible addresses using the arrow keys.  (We have arbitrarily chosen to set all of the Hydras in the department to an address of 3.)
• Then press Enter.