Remote labs in difference to virtual labs allow usually only a single user access. To manage the user access for such remote experiments a reservation system is used. In this work we present our approach to develop a simultaneous multi user access to a lab experiment via clients developed with LabVIEW. This approach was tested for the READ Remote ASIC Design and test System. The software for the creation, verification and possible simulation of circuits and for downloading them to the hardware device is running on an Application Server. In this way the user can remotely download the desired circuit to the device. She can than interact with this programmable hardware via the Internet by setting the parameters of the circuit input (waveform, frequency, amplitude, offset). After the parameters have been set the user can read the circuit output and compare the output signals with the input waveform signal on a virtual instrument on her client PC.
The system controlled by LabView has been implemented using a Data Acquisition Card from National instruments. The performance of the simultaneous access was tested under load with a variable number of users.
Our application follows a client/server model and information is exchanged via TCP/IP protocol. In our server a queue was implemented. User’s requests are queued and processed by applying the desired signal to the circuit under test and returning the measurements. XML is used as a vehicle for this information exchange. All data is converted to XML and transmitted to the server. The server extracts the parameters for signal generation and data acquisition out of the XML string and returns the measurements, also in XML.
Our client was developed also with LabVIEW and is delivered as a stand alone application. A drawback of this solution is that the user has to download and install the proper runtime engine of LabVIEW prior to run the experiments.