The network measurement system is primarily designed for measurements in fields where it is necessary to determine static and dynamic stresses in structures (mechanical engineering, construction, research). However, it can be used anywhere where it is possible to measure using strain gauges, load cells, resistance sensors (potentiometers) or voltage signals obtained in another way. The measurement system is distributed. This means that individual modules (amplifiers) can be placed close to the signal source and the data collected from these modules is sent to the superior system in digital form. In this way, it is possible to limit the influence of electrical interference, temperature, cable length and it can also simplify the installation of the measurement itself.
The system is based on the Measbox EMS-ETH and EMS-PLC measuring modules and the measuring software – ADclient program (MS Windows). Communication is based on the standard TCP/IP (IPv4) protocol within the local computer network (LAN). The modules are designed to measure electrical signals of the millivolt level (strain gauges, load cells, scales, or Pt100 thermometers) and to measure voltage signals in the range of 0 to 5 V (e.g. potentiometric sensors, acceleration sensors). The sampling frequency is adjustable from 4000 to 16000 samples/s per channel. Each module has 8 differential analog inputs. Each input has 4 ranges (two millivolt and two volt). The typical power consumption of the modules is 2 to 4 W and therefore the system is also suitable for battery power.
EMS-ETH modules are connected with a standard Ethernet cable and are powered by POE (Power Over Ethernet IEEE802.3af). The maximum length of Ethernet cables within one switch is limited by the standard to 100 m. This limitation can be circumvented by connecting with an optical cable. The modules can also be connected to an existing local area network (LAN) if the switches provide POE power, or the modules are powered in another way. The modules also have 2 digital inputs of the RS232 serial line for selected types of sensors (GPS, pressure sensors, inclinometers, anemometers, etc.). The sampling frequency of the serial input is 100 Hz.
EMS-PLC modules have two-wire power supply and data transmission (two-wire or coax, 48-57V DC, PLC IEEE 1901). These modules do not have a serial input and an ETH2PLC converter is required to connect them to the system.
The setting of the measuring modules and the actual measurement is performed by the ADclient program, which allows recording, on-line mathematical processing, display and possibly printing of the processed signals. The program can simultaneously process data from max. 32 modules (i.e. approx. 250 measured channels). Off-line evaluation of the measured data is possible by the ADanal program or another commercial product. The format of the recorded data is open.
Example of a network measurement system layout:
