Project published at NI Arabia Developers sitehttp://digital.ni.com/worldwide/arabia.nsf/webcustsol/C6A1FC38C7935CF0862572D1006BF8AE?OpenDocument&node=160320_us
Building an application for measuring impedance under controlled temperature
Author: Eng. Tarek El Afandy (SW Developer), Title Operation Manager, Physics Department, American University in Cairo, Egypt
1-NI GPIB 488.2 USB Hardware
2-NI Measurement Studio /Visual C++ 6.0 Software
3-Fluke PM6306 Impedance meter
4-Lakeshore 331 Temperature Controller
The Measurement Studio for Visual C++ 6 is used to create the application which has
Front End, two exclusive dialog box designed for Displaying the following :
· The Fluke RLC meter :
1- The Frequency set at which the measurement occurs.
2- The Resistance , Capacitance, Inductance, Phase, Quality, Impedance and the Dissipation of the sample being measured.
· The Lakeshore Temperature Controller:
1- The sample temperature read values.
2- The control to set the point at which the temperature reaches.
3- The control the Heater Range
4- The control to set the Heating Ramp Rate.
· The Application sampling rate
Using a PC Timer of 1000 ms as default and up to 60000 ms ( minute).
B-Business Problem Solving Logic (Middle-ware)
To analyze the sample, we need to control the temperature of the environment and the frequency too. Then we read the variables at the sampling rate and let store the results in a file for later Processing. The GPIB Interface enables the communication between the PC and the two instruments (Fluke and LakeShore) to take place .
C- Storing Experiment Data Results (Back-End)
The data collected during the experiment run including the set data (control) and the captured data (read) all are stored in temporary arrays then saved into text file for later manipulation and processing . Excel is a perfect choice to import the data and view its values in table or graph format. This gives greater flexibility for any one who wants to view the data stored in a text file in his perspective and make it portable for further manipulation.
NI supplied a very unique middle-ware above the Operating System (windows) ,ActiveX interface component named CWINSTR.OCX which communicates with any installed GPIB interface detected by NI Max explorer. Any Instrument attached, holds an instance object named (GPIB1,2,..n) where each object has two variables :
o A control variable that processes commands like read, write,.. etc
o A text member variable that holds text strings returned by the GPIB object query.
Two instruments means two objects instantiated, each will hold a unique address and a different communication pattern, pertains to the instrument.
The programmer must first study the GPIB proprietary instrument commands then decide what the user interface must include to display and control the instrument.
Programming skills help the developer in writing the proper code to match between what the user interface dialog is showing and the equivalent C code handling the instrument GPIB Language.