The Challenge:

Implementing a PC-based Data Acquisition system, which acquires temperature & pressure data from thermocouples & pressure sensors respectively connected at different parts of the Heat Transfer Rig. Once the Rig picks up its run, it generates heat. The temperature & pressure should then be continuously monitored. The pressure data comes from the ScaniValve® modules connected. The acquired data should also be published onto different clients.

The Solution:

Developed a reliable and highly accurate Data acquisition system using SCXI- Signal conditioning System (SCXI-1000 Chassis, SCXI-1102 Modules), high speed features of Data Acquisition Card (PCI-6034E) & Software using LabVIEW6i.

Introduction:

The Data acquisition system is designed to perform reliable and highly accurate temperature as well as Pressure measurements. The Heat Transfer Rig’s temperature & pressure is continuously monitored at different locations. After fuel is injected to the rig, the pressure & temperature changes instantly. The pressure data is acquired from scanivalve® modules. The Scanivalve Modules used here for the acquisition of Pressure data are from DSA 3200 series, which is a Digital Sensor Array, it transfers data through the Ethernet using TCP/IP protocol. These modules are identified by a unique IP addresses. The modules, which are connected, are detected & data from the same are acquired. This is a very critical measurement application that runs 3-4 hrs. The system should reliably acquire the data with the corresponding time stamp every second without any data loss.

System Configuration:

The Data acquisition system uses four SCXI modules (SCXI-1102), which is interfaced to the DAQ card (PCI-6034E) in the System. Each Module is connected to the Terminal Block TC-2095 through a shielded cable. This configuration provides the option for the user for using it as a 32-channel Temperature system with a single module and up to 128 channels with all four modules. DSA 3200 Series Scanivalve pressure Measurement system provides 16 pressure channels of pressure measurement. Eight such modules provide 128 Channels of pressure measurement.

System Implementation:

The software of the system is basically divided into 3 Modules Configuration, Acquisition & Display modules.

Figure 1 shows the Settings the user can make in his configuration. The user can select each channel from the List & set the properties for it. Once the User clicks the Save button. The corresponding Settings will get updated. In the configuration module, the user can select his desired channels for acquisition & can set the properties of the each channel being selected. The user can even choose an existing configuration & can edit it and use for acquisition. By default the Last loaded configuration is selected & run unless the user desires a change. The user can set properties for each channel he selects such as its Identification name, Type of sensor & temperature/pressure unit, Alarm limit for each value.

The user then has to decide on his rate & format of logging before starting acquisition. Acquired data are then logged according to the format selected by user the moment the user starts his acquisition. During the run, the user can perform Demand logging for run based on a Specified Time or on certain number of records.

During acquisition the data from the Temperature modules as well as data from the scanivalve modules through which pressure data is acquired is logged onto the format selected by user simultaneously. Once the user in his configuration selects the scanivalve Module either 16 or 8 channels will be selected according to the scanivalve model. The properties of the channels for scanivalve are also editable & the user can edit the properties in normal fashion

Figure 2 shows one of the display screen provided to the user for monitoring. The data being displayed are acquired on-line. The user can select the channel to monitor by clicking the Setup button. A dialog box then prompts the user to enter the Modules & Channel numbers for which he wants to monitor data.

In the software provided, there are six different display screens provided. The user can monitor the data values from different parts of the rig, where the thermocouples & Pressure sensors are connected. The user can give an identification name for each channel, so that he can know the location of the sensor. The data being acquired & displayed can also be monitored on different systems. The client system has to specify the IP address of the host Machine & once the user enters the Host machine’s IP address, the data is also published onto that system. The host PC has the control to give access to the other machine.

Conclusion:

The PC-based Data acquisition system shown in Figure 4 is capable of acquiring the temperature data from the Rig. It provided high accuracy (±0.6°C) of the Temperature values being acquired. The system is also extremely flexible that if a new module is being added, it automatically detects in the program & performs acquisition. This system provides a common software to monitor both pressure and temperature of various parts of the rig.