- Piezometers (8)
- Inclinometers and Tiltmeters (29)
- RDS Railway Deformation System (7)
- Pendulums (1)
- Settlement Gauges (10)
- Pressure cells (5)
- Load Cells (3)
- Extensometers (2)
- Crackmeters and Jointmeters (1)
- Strain Gauges and Thermometers (3)
- Readout units and dataloggers (49)
- Cables, Accessories and Software (2)
RDS Railway Deformation System
All SISGEO digital gauges can be settled in two different powering mode:
- ALWAYS ON: all digital sensors switched on together. Faster solution, but high power consumption. The system will take about 1 second to read each gauge.
- TIMED: the sensors are powered and switched-on one by one. Reading of the chain take more time than "always on", but the power consumption is lower. In this case the system will take about 3 seconds to read each gauge.
The STANDARD powering mode is ALWAYS ON, so unless otherwise requested by the Customer, the sensors are settled as default in ALWAYS ON.
The theoretical maximum number of digital gauge (RS485, ModBus) that is possible to read with New Leonardo is 245 gauges (address from 1 to 254).
This is true only if the gauge is configured in Sisgeo laboratory in "Energy save" mode: the gauges wake-up and are powered one by one.
When the "Energy Save" mode is NOT active, the maximum number of digital gauges in the same chain that New Leonardo is able to read is 50.
The cable lengths depend from many factors, first of all installation and cable protections (screen, earth, etc...). Assuming that instruments are installed in a workmanlike, for the maximum cable lengths should be followed the next suggestions:
DIGITAL INSTRUMENTS: see FAQ#073
ANALOGUE INSTRUMENTS: see both documents:
Cable length guide line with internal multiplexers
Cable length guide line with external multiplexers
FAQ#076 - Why it is necessary add a termination resistor to the last digitized sensor of each RS-485 chain?
All SISGEO digitized instruments (IPIs, Tiltmeters, H-Level…) use the RS-485 serial communication protocol
The RS485 protocol contemplate a termination resistor.
The recommended chain connection is point-to-point (multidropped) nodes as a bus mode (line). Star, ring or multiply network connection are not recommended.
SISGEO dataloggers has already a termination resistor assembled (typically 120Ω). On the opposite side (sensors side) is necessary to mount a resistor on the last device of each chain.
Without termination resistors, reflections of fast driver edges can cause multiple data edges and consequently data corruption. Termination resistors also reduce electrical noise sensitivity. The value of each termination resistor should be equal to the cable characteristic impedance (typically, 120 Ω for twisted pairs and for only one chain).
SISGEO supply the correct termination resistor (120 Ω, 240 Ω, etc.), considering the number of the chains connected to the same master unit (i.e. OMNIAlog).
The termination resistor must be connected on the appropriate sensor connector.
At the following link an example scheme:
All SISGEO digital sensors (IPIs, Tilt-meters, RDSs, H-Level etc..) use the serial RS-485 communication protocol.
The SISGEO digital sensors are joined through an electrical cable, so only one cable is used to take reading.
In agreement with Customer, they are configured in factory for:
- Calibration parameters
- Serial number
- RS-485 andress. Each digitized sensor has a univocal address also reported in a label on the cable.
- Powering type:
- always on (all digitized sensor switched on together). Faster solution, but high power consumption.
- timed (the sensors are powered and switched on one by one). Reading of the chain take a little bit more time than "always on", but the power consumpion is lower
- Measuring units
The sensors are read connecting the end cable to a Modbus Master unit (i.e. OMNIAlog or miniOMNIAlog) with RS-485 interface (DCE, Half duplex, no Echo) able to manage communication with SISGEO Modbus RTU communication protocol.
SISGEO’s communication protocol is available for the release upon request.
The power [W] of power supply must be chosen according to the sensor quantity and power supply mode.
SISGEO suggests not to change the parameters set in factory (serial number, calibration, factors etc..)
The Modbus master unit (readout unit) must be set according to the IPI’s factory sensor configuration.
FAQ#073 - Which is the maximum number of digitized sensors (RS-485, Modbus), the maximum number of chains and the maximum length of cable in a RS-485 network?
All the SISGEO digitized sensors (IPIs, Tilt-meters, RDSs, H-Level etc..) use the serial RS-485 communication protocol.
1.The maximum number of digitized sensors in a RS-485 network are 250 (theoretical)
2.The maximum number of digitized sensors chains that is possible to connect to Modbus master unit (as OMNIAlog or miniOMNIAlog) are 4.
3. About the maximum distance (with digitized sensors configured in "Always On") :
a. max. 250m (in one chain) from the 1st digitized sensor to the last sensor (physical cable length) and:
- 50 digitized sensors for Tiltmeters and H-Level
- 70 digitized sensors for RDS, BH-Profile and IPI
b. max. 1000m from the 1st digitized sensor to Modbus master unit (as OMNIAlog or miniOMNIAlog) with a suitable cable size, cod.WE606IPDZH)
NOTE: The sum of 3A and 3B lengths can’t exceed 1000m. The compliance of points 3A and 3B, avoids the excessive voltage drop on the RS-485 line and guarantees the correct RS-485 network operation