You can program the Hydra in LabView  The specific LabView program here takes a single DC voltage measurement.  At the end of the lesson you can modify the program to measure a single temperature.

• Given a Hydra and a Wintel computer,
• Be able to write LabView programs to measure DC voltages.

        Before you can do measurements, you need to take care of the following points.

• The Hydra should be turned on.
• The Hydra and the computer should be set so that they can communcate.

• Start LabView on your computer.
• Write a sequence of commands to the Hydra.  The commands you need to write are:
• *RST
• FUNC 0,VDC,AUTO
• *TRG
• LAST? 0
• To write these commands, you need to use the GPIB Write function.  It will look like this when you place it on the Block Diagram.
• 
• The function is found on the Functions Palette under Instrument I/O-GPIB.
• Place four GPIB Write functions on the Block Diagram and wire them.
• The address for the Hydras in Lab should be 3.
• Use mode 3 to append a carriage return and line feed to the end of each command string.
• Wire the error signal from the first GPIBWrite function to each succeeding function.  That ensures that the GPIBWrite functions operate in the correct sequence.
• Then read the data using a GPIB Read function.  It looks like this.
• 
• Finally, the output of the GPIBRead (a string) can be presented to the user with a String Indicator on the front panel.
• When you're done, the result will look like the diagram below.

        Note the following about this program.

• The first operation is to write a string - *RST - to the Hydra.  The write operation is similar to ibwrt in other programming languages.  Here you use a GPIB Write block.
• Note that you do not use the string "Hydra" to identify the Hydra in LabView.  Instead, you use the IEEE-488 address set on the Hydra.  That value is 3 and is set in the pink string constant.  Note that the blue numeric constant sets the mode so that a CR and LF are appended to the string when it is sent.
• This program sends four strings/commands to the Hydra.  Click here for a quick review of the commands for a single DC voltage measurement.  The strings are:
• *RST
• FUNC 0,VDC,AUTO
• *TRG
• LAST? 0
• To get the measurement into the computer, use the GPIB Read function.  Here the program allows for a 20 character string and when the string is read the string shows up in an output text box which can be seen on the panel view.

• First, note that temperature cannot be measured from the front panel - Channel 0 - and you will have to use one of the other channels.
• Here's a command string you can use.  This sets the Hydra for a temperature measurement.  Everything else can stay the same in the program.
• FUNC 1,TEMP,K
• This will measure TEMPerature using a type K thermocouple connected to Channel 1 on the connector strip cemented to the top of the Hydra DAU (See below.).  You cannot measure temperature using a thermocouple and the front panel connectors.