- Piezometri (10)
- Inclinometri e pendoli (33)
- Sistema monitoraggio binari RDS (8)
- Pendoli (2)
- Assestimetri (14)
- Celle di pressione (7)
- Celle di carico (6)
- Estensimetri (6)
- Fessurimetri e misuratori di giunti (3)
- Barrette estensimetriche e termometri (4)
- Centraline e unità di acquisizione (60)
- Cavi, accessori e software (3)
Celle di pressione
FAQ#111 - Why I cannot read correctly my 4-20mA current loop gauge?
It could be a problem connected to the power supply given by the readout or logger. When the power supply is in the current loop (2-wire gauge) it is necessary to consider the effect of voltage drop across the shunt resistor on the voltage applied to the gauge.
For example, suppose a 4-20mA gauge requires at least 12 V to operate correctly and the readout powered with 16 V. The voltage the gauge sees is the voltage supplied by the readout minus the voltage drop in the rest of the current loop. At 20 mA output, the voltage drop across the commonly used 100 ohm resistor is 2 V.
When the voltage supplied by the readout is 16 V, this leaves 14 V for the gauge and everything is fine.
However, if the readout is powered with less than 14 V, at 20 mA current it will leave less than 12 V for the gauge. In this case, the output of the transmitter may be in error.
FAQ#110 - What's the purpose of the linear and polynomial factors written in the Calibration Reports?
Utilize the Linear Sensitivity Factors (A, B) and Ploynomial Sensitivity Factors (A, B, C, D) of the Calibration Reports permit to obtain readings in engineerig units with a maximum error as for the Calibration Report.
In the case of analogue gauges, the factors shall be applied on the electrical readings (i.e. mA, mV, digit, etc...)
In the case of digital gauges in "Legacy mode" (digital gauges with FW version 0.X, 1.X, 2.X or 3.X), the factors shall be applied on the output in engineering units (i.e. sin angle, kPa, etc...)
In the case of digital gauges in "Normal Mode" (digital gauges with FW version 3 or higher), the factors are already applied inside the gauge, so the Sensitivity Factors shall not be utilized with these instruments.
NOTE: all the new digital gauges are in "Normal mode".
For more information regarding SISGEO Calibration Report, refer to the following video https://youtu.be/BF8e3ZRcaYU
For more information on "how to use" the Sensitivity Factors with analogue gauges and with digital gauges in Legacy Mode, refer to the instruments manuals or to the following document: https://www.sisgeo.com/uploads/manuali/Addendum_data_processing/ADDENDUM_-_DATA_PROCESSING_-_EN_00.pdf
FAQ#077 - Which are the maximum cable lengths from instrument to datalogger?
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#030 - Why do the NATM pressure cells have repressurizing tubes?
NATM pressure cells are normally used to measure tangential and radial stresses in concrete tunnel lining. They are embedded in concrete and after curing the cell shall be repressurized to mantain the intimate contact between the pessure pad and the surrounding material.
FAQ#022 - Why NATM pressure cells have repressurizing tubes?
NATM pressure cells are normally used to measure tangential and radial stresses in concrete tunnel lining. They are embedded in concrete and after curing the cell shall be repressurized to mantain the intimate contact between the pessure pad and the surrounding material.
FAQ#021 - Is the repressurizing hand pump for NATM pressure cells filled by de-aired oil, ready to use? Which kind of oil is used for this purpose?
Yes it is. The pump is filled at factory under vacuum with de-aired oil. For normal use within concrete the oil inside the pump is enough to repressurize 50 pcs. of NATM pressure cells. The oil we use is Edwards Ultra-grade 19 type for vacuum-pump use.
FAQ#020 - How to obtain better results from pressure cells installed in earthfill?
The measurement of total pressure in geomechanics, even if is one of the most interesting parameters for the designer, is generally considered not reliable. Case histories report more nonsuccessful examples than for all the other types of measurements. Theoretical studies made by many researches have highlighted the critical parameters in the design and manufacturing of pressure cells. If the instruments are accurately designed and manufactured and the choice of the model has been done properly, the problem becomes how to use the cell.
In the paper presented by Mr. D. Bruzzi and Mr. A. Zattoni (SISGEO) and Mr. G. Pezzetti (ISMES) at 5TH International Simposium FMGM/99 in Singapore, the authors discuss the main issues related both to laboratory calibration and field installation problems, and a practical approach is presented in order to improve the quality of the results.
The conclusion is that pressure cells provide relative measures that can become absolute by using simple and practical rules deriving from a good knowledge of the basic problems related to design, manufacturing and installation of total pressure cells. For a complete view of this paper, click here to download the .pdf file.