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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
The Barometer model 0MEPR106000 have a 4-20mA current loop output.
The measuring range is from 800 mbar (equivalent to 4 mA) to 1200 mbar (equivalent to 20 mA).
Manual readings are taken connecting the wires to a readout according to the following instructions:
Signal: 4-20mA current loop
Red: + Loop
Black: - Loop
The following formula allows to convert the electrical measurements (mA) into engineering values (mbar):
Pmbar = Pressure in millibar
RmA = Reading in mA
S = sensitivity as from the Compliance Certificate in mA/mbar (usually 25 mbar/mA)
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#037 - Which is the linear thermal expansion coefficient of the graduated flat cable (tape) of Water Level Indicators (WLI) and BRS settlement probes?
The linear thermal expansion coefficient of the flat graduated cable is 16x10E-6 m/ °C.
FAQ#033 - I have received the calibration Report of a piezometer. There is not the K Thermal Factor noted. In which way may I proceed?
If the value is not indicated in the Calibration Report, you should use this formula: K = -1 digit/°C For each degree of increase of temperature you should reduce 1 digit.
HAE (High air entry) filters are normally used to monitor pore pressure in the clay core dams and saturated low permeability soils. “High air entry” means high-resistance to air entry when the filter is saturated. The surface tension of the water in the very fine porus of the filter prevents entry of air. The HAE filters must be saturated before installation by means of the saturation device.
LAE (Lowair entry) filters are often used in medium and soft soils. They do not need to be saturated by special device because the porosity of the filter permits water entry with simple immersion.
A plasma surge arrestor is wired in parallel with the coil (which is used to pluck the wire). The nominal impulse discharge current 8-20 microsec interval is 10 KA. Impulse spark-over voltage at 1Kv/ microsec: 700 V.
FAQ#017 - Can we buy spare parts for replacement of the water level indicator probe and repair it ourselves?
Yes, we sell a kit which includes instructions, probe, weights, rexin, and any other parts.
FAQ#016 - Are the vibrating wire piezometers equipped with temperature sensors, or is the temperature sensor an option?
Yes, each vibrating wire piezometer, as every Sisgeo vibrating wire instrument, is equipped with a built-in NTC thermistor YSI 44005 type (3000 Ohm at 25°C). Thermistor is not a option for vibrating wire instruments and therefore there is not additional cost for it.