dataTaker : Standardization of protocols and data formats

Interfacing dataTaker

Ever wondered how remote controlling of a large number of instruments work in a given scenario of a big experimental set up such as superconductivity testing or missile launching where a large number of devices need to be handled simultaneously, with very less supply dedicated for it? Standardized protocol and data formats to log data play a very crucial role in addressing these scenarios. One of the pioneer tool in this field is dataTaker. 

-project and article contributed by Adil Wankhede, VNIT, Nagpur. 

What are data loggers?

Data loggers are devices that are used for data acquisition purposes.It acquires data through a variety of sensors,and are best suited to applications that require stand-alone operation in remote or distributed locations where power supply may be limited.It monitors sensors and stores the data until retrieved.Loggers typically only have one A-D converter which means only one sensor is read at a time or in other words the channels are multiplexed.Loggers may have slower sampling rates as compared to data acquisition units.

The ways to interface

dEX Web UI

           dEX datalogger software is a user-friendly graphical interface that allows you to configure your data logger, view real-time data in the form of mimics, trend charts or tables and retrieve your historical data for analysis.dEX is a browser based solution and comes pre-installed on every logger in the DT80 range.

Detranfer

           Text based terminal program for programming and viewing data from any dataTaker data logger. Programming is done using dataTaker command language.It makes use of simple mnemonics and offers great deal of functionality.

LabVIEW DT8x library

          LabVIEW is National Instrument's leading graphical software development environment for measurement and automation applications.The dataTaker DT8x Driver is a comprehensive library of VIs that allows dataTaker DT8x range data loggers to be configured and queried from LabVIEW.It provides a means to incorporate dataTaker data loggers in applications that require an open, programmable software environment, with other I/O hardware.

Detransfer coding basics

Schedule structure

Schedules are the underlying structures used to manage the repetitive processes of the DT80.So all device configurations called jobs are written inside a schedule that can be triggered as fast as every 10ms to a number of days.There are total 11 general purpose schedules A-K executed in order of priority.

Channel variables

Channel variables (CVs) are memory locations (registers) for holding and manipulating floating-point data. The DT80 has 1000 channel variables, identified as 1CV to 1000CV.

Sample Code   

BEGIN”Name”                                      Start Program

RA5S                                                      Run schedule A 5 Second rate 1DNO(“WRITE”)=12                            Write to digital channel 1

1TK                                                        Channel 1 TC type K (+-)

RB10S                                                    Run schedule B 10 Second rate

1V                                                           Channel 1 Voltage (+-)

2*R(“Resistance~ohms”)                       Channel 2 Resistance(*#)

END                                                   

LOGON                                                  Start logging

Structure of DT8x Library

     It is based upon standard LabVIEW conventions for designing libraries.The driver palette is organised in three levels – High (or Easy), Intermediate, and Low (or Advanced).The high level palettes provide “single VI” solutions to the task of retrieving real-time or historical data from a dataTaker data logger.But for configuring dataTaker we need to use lower level blocks.

Labview code

Front panel

Block Diagram

  

Achieved functionality:

·       Multiple channels can be configured to monitor simultaneously.

·       Any code can be written to the logger similar to detranfer

·       Both TCP/IP and serial communication are possible.

·       Data can be logged in a file for trend analysis and future use.
      dataTaker proves out to be a useful tool while interfacing a number of instruments with ease of handling.

      -project and article contributed by Adil Wankhede, EEE, VNIT.           

     (the model and the codes written go into the thesis written at IIT Kharagpur and was done under the guidance of Prof. V. V. Rao)