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- Readout units and dataloggers (60)
- Cables, Accessories and Software (3)
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#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?
Last update: October 2021
All the SISGEO digitized sensors utilize a RS485 interface with Modbus protocol.
1.The maximum number of digitized sensors in a RS-485 network are 247 (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 number of sensors in a chain and lengths, please follow the next tables:
NOTE: The sum of “A” and “C” lengths can’t exceed 1000m. The compliance of points A and B, avoids the excessive voltage drop on the RS-485 line and guarantees the correct RS-485 network operation.
FAQ#034 - Is possible to repair/change the manometer without disassemble the load cell?
It is not possible to repair/change the manometer without disassemble the load cell. The scope of the glycerine inside of the manometer display is only to show eventual tampering of the manometer. The load cell work properly without glycerine, too.
FAQ#015 - The anchor load value displayed on the load cell manometer or readout does not agree with load calculated by the hydraulic jack. What's right?
The main factors which influence the anchor measurements are:
– axial misalignment of the jack
– difference in diameter between the jack and the load cell.
These factors cause bending of the bearing plate between the load cell and the jack and affects the response of the cell. To minimise this effect use the genuine distribution plate which loads properly the sensitive upper ring of the load cell.