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A Mobile Data Acquisition System for Engineering Use A Mobile Data Acquisition System for Engineering Use M. Galuška, V. Vacek, M. Doubrava [email protected] [email protected] CTU, Faculty of Mechanical Engineering, Department of Applied Physics Technická 4, 16607 Praha 6 © 2006 M. Galuška, V. Vacek,, M. Doubrava ABSTRACT: ABSTRACT: The components being developed for measurement applications in the European laboratory for particle physics research – CERN – can be used to make a very compact and mobile data acquisition (DAQ) system for various engineering measurement needs. As a supplement to the longstanding cooperation of the Department of Applied Physics with CERN, which cooperates on the development of an evaporative cooling system for the LHC ATLAS Inner Detector, these components have been appropriately adapted and a Mobile DAQ System for engineering use has been created. The CERN standard for most engineering measurement applications comprises, from the point of view of hardware, a personal computer or server, CAN-Bus communication architecture, and up to 64 ELMB (Embedded Local Monitor Board) units. From the point of view of software, of an OPC server for communicating via the CAN-Bus, and OPC clients on the same or networked computers to read, display, and store the measured data. The ELMB unit comprises a 64-channel analog DC-voltage multiplexer and four flat-cable connection plugs (16 channels per cable). Each cable connection is provided with plugs for signal adaptation to enable reading not only voltage signals, but also resistance signals in either 2- or 4- wire connection modes. This provides the ability to read temperature sensors of Pt1000, Pt100, and NTC types, thermocouples, pressure sensors, flow meters, and various other electronic measurement instruments. With the advance of processing power of notebook computers and the development of the USB interface, the opportunity arose to fit the mentioned OPC server, which administers the communication of the computer with the ELMBs, and the OPC client, which administers the user interface with the measured data, into one machine, connected to the CAN-Bus via an external USB CAN card. Together with a common AC/DC adaptor to power the ELMBs and CAN-Bus, and some cabling, a fully-functional, independent, very compact DAQ system can be created, that can fit into a single briefcase or larger notebook handbag, able to measure up to 64 channels with each ELMB unit used. Such a Mobile DAQ System has been created at the department, along with software in the PVSS environment (OPC Client). The software allows controlling up to four ELMB units, configuring their channels, creating graphical layouts and plots for easier experiment or process visualization and control, record and store measured data, and output the data in Excel spreadsheet format, all by a user inexperienced in programming or without detailed knowledge of the PVSS and OPC environment. The ELMB units have been adapted so as to measure 16 Pt1000-type sensors, 16 NTC-type sensors, 16 voltage-output sensors, and either 8 Pt100-type sensors in four-wire connection mode, or another 16 NTC- or Pt1000-type sensors. Therefore, with all four ELMB units connected, the system can display and record data of up to 192 temperatures and 64 pressures, flows, or other quantities measured by sensors with voltage output. Nevertheless, this configuration can be changed simply by changing the signal adapters on the ELMB units and modifying the appropriate conversion equations within the software. Measured data are displayed and stored about every 5 seconds. The data can be retrieved and output into an Excel spreadsheet file even at a later date, with the user choosing the time-span for which the data should be retrieved, and the interval at which the data within the time-span should be output – for example every 5, 10, 15, or 30 seconds. The system has been successfully tested and used for experimental measurements for sensor calibrations and on cooling system prototypes. Summary: • A fully mobile data acquisition system based on CERN standard components has been created • Capable of using up to four ELMB units, therefore measure up to 256 sensors Summary: Summary: • A fully mobile data acquisition system based on CERN standard components has been created • Capable of using up to four ELMB units, therefore measure up to 256 sensors DAQ System Administration DAQ System Administration DAQ system architecture DAQ system architecture - CERN standard for engineering measurements CERN standard for engineering measurements - CAN CAN- Bus Bus – industrial standard industrial standard architecture. For short distance architecture. For short distance applications, a 9 applications, a 9- wire flat cable is used wire flat cable is used with Canon connectors. with Canon connectors. ELMB ELMB – 64 analog channels = four 34 64 analog channels = four 34- pin pin flat cable plugs. Two pins per channel + 2 flat cable plugs. Two pins per channel + 2 pins for reference voltage (2.5V) on each pins for reference voltage (2.5V) on each cable plug. cable plug. CAN CAN- Bus Bus – computer computer Interface uses an Interface uses an external USB CAN external USB CAN- Bus Bus card, e.g. card, e.g. Kvaser Kvaser USBcan USBcan II. II. Power is provided Power is provided externally for both the externally for both the CAN CAN- Bus and the ELMB Bus and the ELMB using an ordinary 9V using an ordinary 9V AC/DC adaptor that plugs AC/DC adaptor that plugs into the mains. into the mains. Ordinary notebook PC Ordinary notebook PC running Microsoft running Microsoft Windows. Windows. Σ Σ = = The Mobile DAQ System The Mobile DAQ System • Fits into a suitcase or a larger notebook computer handbag • Can connect up to four ELMBs, each providing 64 analog input channels a potential to measure 256 sensors PVSS II PVSS II (ETM, Austria) (ETM, Austria) • Graphical, object-oriented programming environment • Monitors and manages the CAN-Bus network and ELMB units through the OPC Server • Reads measured data from the OPC Server • Can manipulate data – recalculate, use in other calculations • Displays data – display windows, graphs and plots • Monitors data – reacts to value changes, warns and displays alarms if readings are too high or too low • Stores data in an internal database • Outputs stored data in Excel format for any time-span (even past measurements), at various data intervals (e.g. every 5, 10, 30 seconds, etc.) OPC Server OPC Server (ATLAS DCS, CERN) (ATLAS DCS, CERN) • Administers the communication via the CAN-Bus • Other software using the measured data connects to the OPC server, not directly to the ELMBs • Can manipulate measured data, e.g. perform calculations, such as computing the temperature from the data provided by a temperature sensor • Is configured using a simple text file, or though the Mobile DAQ PVSS project developed by the Department Back side of the ELMB Back side of the ELMB Contains plugs for special signal adapters, allowing the connection of various types of sensors: • 16 Pt1000- or NTC-type temperature sensors per cable • 16 voltage signals per cable (maximum input voltage depends on range setting of ELMB, can be up to 500V) • 8 Pt100- type temperature sensors connected in 4- wire configuration per cable OPC Server OPC Server configuration utility: configuration utility: Definition of sensors, Definition of sensors, their conversion their conversion equations, and their equations, and their assignment to assignment to channels channels Utility for configuring Utility for configuring measured channels: measured channels: Units, significant Units, significant digits, description, digits, description, warning and alarm warning and alarm ranges ranges Export of measured data Export of measured data Measurement Visualization Measurement Visualization Pre Pre- prepared channel display prepared channel display windo windo – the user only specifies what channel the user only specifies what channel to display. The appropriate to display. The appropriate programming link to the channel programming link to the channel description, unit, warning and alarm description, unit, warning and alarm ranges, and archiving status is ranges, and archiving status is created automatically created automatically Pre Pre- prepared graphs prepared graphs – the user the user only lists the channels to be only lists the channels to be plotted and the scale range. The plotted and the scale range. The programming links are made programming links are made automatically. automatically. Technical Information about the ELMB • 64 channel multiplexer for analog DC signals • 16-bit A/D converter • Measurement in units of microvolts • 25 mV, 55 mV, 100 mV, 1 V, 2.5 V, and 5 V range settings • Unipolar or bipolar measurement • 7 conversion rates from 1.88 Hz to 101.1 Hz • Supply power 9 – 12 V DC Technical Information about the ELMB Technical Information about the ELMB • 64 channel multiplexer for analog DC signals • 16-bit A/D converter • Measurement in units of microvolts • 25 mV, 55 mV, 100 mV, 1 V, 2.5 V, and 5 V range settings • Unipolar or bipolar measurement • 7 conversion rates from 1.88 Hz to 101.1 Hz • Supply power 9 – 12 V DC Calibration Calibration Using known resistance and voltage inputs Using known resistance and voltage inputs (measured precisely using laboratory (measured precisely using laboratory multimeters), the output of the ELMB is multimeters), the output of the ELMB is corrected for slope and deviation if necessary. corrected for slope and deviation if necessary. The CTU Mobile DAQ system can measure: The CTU Mobile DAQ system can measure: • temperatures to an accuracy of temperatures to an accuracy of ± 0.1 0.1 °C • voltage signals to an accuracy of voltage signals to an accuracy of ± 0.01 V 0.01 V (Typical values – depends on sensors and signal adaptors used, and on the ADC settings of the ELMB (range, conversion rate)) Cable plug for supply all 16 channels of a cable with identical controlled voltage Cable plug for supply all 16 channels of a cable with a known resistance (precise miniature resistors) • Transportable within a briefcase or notebook computer bag • Graphical presentation, channel setup, and data extraction can be performed by users without thorough knowledge of any of the components (CAN-Bus, OPC, PVSS) • Transportable within a briefcase or notebook computer bag • Graphical presentation, channel setup, and data extraction can be performed by users without thorough knowledge of any of the components (CAN-Bus, OPC, PVSS)
