foto assistance sisgeo1150 320

Crackmeters and Jointmeters

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.

Wire Deformeters
MEMS In-place Inclinometers
Wire Crackmeters
Multipoint settlement gauges
MPBX - Multipoint Borehole Extensometers
MEXID Miniaturized MPBX
Fixed Extensometers
Electric Anchor Load Cells
Earth Pressure Cells
Electro-hydraulic Load Cells for Steel Linings and Struts
Crackmeters and Jointmeters
Mini OMNIAlog datalogger
Flat Jack Testing Accessories
Solid Resistive Load Cells for Pile Testing
H-Level - Liquid Level Systems
Convergence extensometer (DISCONTINUED)
Piezo-Resistive piezometers
Vented pressure transducers
Removable pressure transducers
Titanium piezometers
Drive-in piezometers
MEMS Analogue Tilt Meters

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

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:



MD-Profile system

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:


ANALOGUE INSTRUMENTS: see both documents:

Cable length guide line with internal multiplexers
Cable length guide line with external multiplexers




MD-Profile system