Data Logger and Controller using CompactDAQ and LabVIEW

 

 

Data logger and controller using CompactDAQ and LabVIEW.  An automotive test lab needed a general data logger and digital controller to perform tests on their products.   The system needed to monitor thermocouples, accelerometers, voltages, and a rotary encoder.  Low and high limits needed to be assigned to the analog inputs, and if the measured value exceeded the limits the software would report a fault.  The software had to also control digital outputs.   The software needed to turn on and off digital outputs for a user specified time in a user specified sequence.  Each digital output needed to controlled independently.  

 

The customer wanted to use off the shelf data acquisition hardware to reduce costs and standardize the hardware in the lab.  The hardware also needed to be able to measure different signal types i.e. thermocouples, thermocouples, and voltages.

 

The software needed to be able to add additional features to accommodate changing test requirements.

We developed a custom LabVIEW application using NI Compact DAQ hardware.  A CompactDAQ system has a chassis that is connected to a PC through USB or Ethernet, and then populated with one or more conditioned I/O modules that provide direct sensor connectivity. 

 

This is the dialog screen that allows the user to set up the software.  From the setup dialog the user could specify the test options and all the hardware channel address and properties.  We used an object oriented approach that allows us to add or remove groups of options easily if the software needed to expand.

 

 

Shown here is how the user can set up Voltage channels.  The user can set the channel name, physical hardware address, full scale value of the channel, engineering units, and calibration options.

 

 

This is an example of the analog input hardware channel calibration.  The user can enter data from the calibration sheet directly into the table.  A graph is plotted to make sure the entered values were correct.

 

 

The sequence editor allowed the user to set up a sequence on a digital output.  The user could specify what digital output to control, what would trigger the start of the sequence (button push or external digital input), and what would happen when a sequence ended.  The user had the ability to add steps to a sequence.  Each step would hold the digital output at a defined state for a specified time.  The software would run though the steps the number of cycles entered.  Up to 4 sequences could be run independently of each other.

 

 

The limit dialog allowed the user to specify fault limits on hardware channels.  Shown below is the limits for the Analog Inputs.  The channel names set up in the settings dialog are loaded into the channel names of the limit dialog.  The user can specify a digital output channel to activate if the limit is exceeded.  The user was able to modify the limit dialog while the test was running.

 

 

The data from the test was saved as a comma delimited file (CSV).  This file format can be read by any analysis program such as excel.

 

 

Result