A device that measures autonomously the basic quantities of a large machine (eg. radial compressor). If the set limit values are exceeded, it archives data measured before and after exceeding the limit values and sends a warning message to the production plant. Last but not least, it enables remote measurement and data evaluation.
The system performs the following tests:
- Temperature test: temperature measurement at about 60 locations.
- Vibration test: dynamic measurement at about 30 locations with a sampling rate of up to 50 samples per second and simultaneous sampling on all channels.
- Electrical test: measuring 0-20 mA signals, approx. 10 channels.
- Electromechanical test: measurement of pressures, flow rates, etc., when the measurement is again a 0-20 mA signal, about 5 channels.
- Internal test: measurement of one channel with sampling frequency 100 kSa/s, signal amplitude is ± 20V.
- Transient measurement: measurement of several channels with a sampling frequency of 51 kSa/s with the possibility of increasing the sampling frequency while decreasing the number of measured channels. This test is not performed automatically, only on operator request.
- Accurate frequency measurement: it is also performed only at operator request, running on several channels.
The 5B series single-channel modules are used to power the sensors and adjust the signals from them. 5B is the de facto standard commonly used in many measurement and control applications. Modules 5B are “cubes” of a specified size, equipped on one side with a standard connector that plugs into the module carrier. Modules for measuring various quantities do not differ in size or connector, so that by simply replacing the module it is possible to immediately change the type of measured quantity on a specific channel (eg. from Pt100 to a thermocouple). All channels are galvanically isolated (with an insulation strength of several kiloVolts), which greatly helps eliminate interference problems on ground loops. The use of standard 5B signal conditioning modules makes it possible to include sensors without electronics in the measuring chain, where appropriate, significantly reducing the cost.
The modified signals are input to a 120-channel Tektronix VX4330 multiplexer. It multiplexes the voltage to the input of a precision 5½-digit multimeter and Tektronix VX4101 counter. The multimeter controls the multiplexer itself; the measurement is triggered only after the signal path has been reliably closed.
For dynamic measurements, the system includes a 32-channel 4475 A/D converter, with separate measurements for each channel. Each channel is equipped with its own amplifier, a precision 16-bit sigma-delta converter (ie, 0.0015% of the range) and digital low-pass filter set to 45.5% of the sampling rate (maximum 45.5 kHz). The module enables external triggering of samples, which is advantageous for some measurements on rotary machines (synchronization of samples with the angle of rotation of the rotor). The module is equipped with 68030 processor and FIFO memory for 16000 samples. The module manufacturer specializes in digital processing of NF and HF signals and represents a leader in its field (eg. he cooperates with NASA).
The measuring system is equipped with powerful computer technology. The computer working on the VXI bus (called the “measuring computer”) is primarily designed to collect data from the A/D converter and, based on the set limits and measured values, pre-evaluates the measured data – which are stored and which are not interesting. It communicates with another computer called a “communication computer”. It works as a gateway to the Internet. It serves as an intranet server providing information about the last measured data. It also generates reports when limits are exceeded. Last but not least, it provides communication with the operator, pre-evaluation and data visualization.
The equipment used is based on open standards and does not interfere with the possibility to expand the system. Certain redundancy and dynamic assignment of logical channels to the physical will allow for the solution of possible failures of one channel by applying its signal to another one.
Measuring and communication program provides:
- cyclic sequential performance of individual tests (temperature, vibration, etc.), their evaluation and eventually storing results,
- signal paths setup for each specific test, checking the measuring chain at the moment of deviations from the set limits (to distinguish the actual fault from the sensor fault),
- periodic start of device self-test,
- two-way communication with the operator via the Intranet or the Internet, ie. exposing the measured data on the web page, receiving instructions for performing tests “out of order” and setting new limit values for evaluation.
New technologies bring new possibilities for remote monitoring of equipment directly at the customer promise, while workers do not leave their workplace. Internet has been gradually affecting measurement and is used here as a basic tool of communication between the measuring workplace and the equipment manufacturer’s computer. Intranet, as a special use of the Internet, is a private network within the company. However, it uses the same popular tools as the Internet, ie. browsers, HTML, and dynamic links to other information. Data collection, analysis, and display can be distributed from servers to many remote computers on the Internet just as any other information.
A prerequisite for the effective use of Internet resources is the existence of appropriate tools to link the measuring program with them. Internet and Intranet support is important for this application, which complements the TestPoint development environment.
TestPint Toolkit includes, for example, TestPoint Web Server, which offers the same capabilities for creating measurement objects as the environment itself. However, objects are part of HTML pages. The object also supports graphic formats JPG and GIF. In this case measuring program is viewed by an Internet browser. Measured data are visualized on the communication computer and anyone can view it using an Internet browser.
Another part of the Toolkit is an e-mail client. Applications created in TestPoint can therefore send messages by e-mail, in text form. This option is useful, for example, when sending emergency information to selected e-mail addresses. This client is used for sending reports about exceeding limits.
An important part of the Toolkit is the TCP/IP interface. This interface makes possible to connect any computer with the TCP/IP protocol, which is a standard part of the Internet. The created program can work as a server or as a client. Thus, two programs created in TestPoint can communicate with each other, although each program works on a different computer. It is also possible the measuring program communicates with any TCP/IP-based program. The interface thus enables the communication computer to be connected to the computer in the manufacturing plant, remote data acquisition, setting of the measured object remotely, modification of measurement from the remote computer etc.
The solution has the following main advantages
- automatic and continuous diagnostics, including information about exceeding the set limit values sent by e-mail anywhere,
- cost savings for travel staff; based on running tests and evaluating data from geographically unlimited remote workplace,
- highly reliable solution,
- the morally ageing will be very slow,
- delivery as a whole, guaranteeing the functionality of the system as a whole without the risk of undetected design errors,
- one partner for solving eventual complaints of technology and programs, domestic service,
- open solution allows to combine the most suitable modules into one unit,
- scalable system,
- use of “dry” sensors with untreated output,
- openess to further program modifications,
- direct contact to program authors, hot line,
- each VXI modules is self-test equipped.
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