Troubles with programming a program with different multiple channels!

Question

Dear LabView users,
i've been struggling with a program I need to write about the stress-strain curve and the E-modulus of a material tested with strain gauges, and LVDT's.
The thing is, I need to acquire data with the nDAQ-system from strain gauges (Virtual channel: Strain), LVDT's (Virtual channel: Voltage) AND a pressure cell (Virtual channel: Voltage), and I need to log this data and do some operations with this data. The problem is, this program needs to work with either the combination of 1 strain gauge, 1 LVDT and 1 pressure cell, but also with the combination, for example, of 4 strain gauges, 2 LVDT's and 1 pressure cell. For the strain gauge I need to be able to configure the strain gauge properties (but this is able with the bridge configuration cluster provided by LabView) for each strain gauge seperatly, also I need to be able to configure the scale and the input voltage for each LVDT or pressure cell, also seperatly. And I need to be able to select the channel for each gauge,LVDT and force cell. Also I need to be able to set these elements to zero before the testing begins. 
Thereafter all these data needs to be logged into an excel file and also be shown on a clear graph that shows me the strain from the gauges, the displacement of the LVDT's and the force of the pressure cell. 
Eventually, I need to become a stress-strain curve and the E-modulus of the material we're testing, presented in LabVIEW.
Does someone has an idea about how I should work this out step by step? Any help would be very usefull.
With kind regards,
Peter

Answer 1

PeteTheGod wrote:
You remember my previous post? Is it something like that you mean? I started there also with a cluster with name and scale information, but for the strain gauges it was too difficult to complete this. And eventually, it was getting way to complicated for me to proceed with programming.
And what do you mean with the configuration file? You mean a notebook file like I already tried? 
Do you have some easy example (.vi) about how I should do this? 
Dear Peter,
     I'm sorry, but I did not remember your previous post (though I did remember looking at something you had posted).  However, I did "look it up" and saw that I'd made a suggestion that you store your configuration information in a Cluster, use an Enum (that you define) for the various types of Bridges, and store the data in a Configuration File of some form.  LabVIEW has a series of Functions on the File I/O Palette for .INI files (which it calls "Configuration Files", and I provided an example for using an Excel Workbook as a Storage format, but you can use anything, even a Text file.
     The important thing is this allows you, the User, to have a set of "Details" (Bridge Type, Gauge Factor, Gauge Resistance, etc.) stored along with a Name that you choose, and at Run Time, you can specify or choose just the Name (say, from a Drop-down List) and pick up all of the other parameters from your Configuration File.
     If you were going to use a Drop Down List, you would want to populate it with the "Correct Choices", i.e. the list of Names in your Configuration File.  So your Initialization Code would read the Configuration File and create a Ring (or something similar) populated with all of the Names.  Then, when you choose which Device using the Ring to force you to choose one of the named Devices, you would simply use the Ring value to index your array of Configuration information to get Bridge Type, Gauge Factor, etc.
     My earlier Post was "specialized" in that it only applied to Bridge Specification.  If you want to include other Devices, such as LVDTs, you can certainly do that.  Now your basic Cluster would change -- instead of Name, Bridge Type, etc., which is specific for Bridges, you would have Name, Device Type (an Enum that was Bridge, LVDT, etc.), and perhaps a Variant that could be called Device Specs (my earlier Example shows a possible Bridge Device Spec as a cluster of Bridge Type and two Gauge parameters).
     Do you know about Variants and how to handle them?  It just means a little more processing at the time of Reading, Writing, and Using.  Here the LabVIEW .INI Config Functions might be simpler as you could particularize the sub-parameters based on the Device Type.  You could still use Excel, but you'd need to give some thought about how to handle the different sets of columns for the different Device Types.  If you want to go the Excel route, design an Example Worksheet (similar to the example you showed at the beginning of this post, which was just for Bridges, I believe) and show us your thoughts.
     Spending a little time on design now can really pay off later -- it may take you an extra hour to figure out how to write the code, but the code should take very little time to execute, and will keep your program nimble, effective, and capable of handling multiple and new devices.
Bob Schor