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Hydraulic system for water measuring, sensor calibration and maintenance

During the research project three different prototypes of measuring systems were developed:
- LFA test unit;
- Probe demonstrator;
- Final prototype.

Each of them was practically used in different stages of research to test the results coming from other groups and to perform measurements on water samples.

LFA test unit:
The LFA test unit is based on a standard SYSTEA MICROCHEM bench top analyser, which is able to manage automatically a complete measuring sequence using the patented Loop Flow Reactor (LFR) analytical technology.

The unit is divided into four main sections:
- Hydraulics, mounted in the front view panel

- Electronics and actuators, mounted inside the back panel

- Internal reagents compartment, accessible from the right side of the unit

- Alphanumeric display and membrane keyboard and a printer, mounted at the top front of the instrument.

The standard LFR hydraulic manifold unit was modified to integrate:
- The two-sides back-planed ISFET measuring flow-cell already developed by Warsaw University.

- An Ag/AgCl reference electrode, mounted in the centre of the same measuring head.

- N.2 CHEMFET sensors, referenced to the same Ag/AgCl electrode, with standard MOSFET output.

Modified Front Side contact Sensors from LAAS partner technology, mounted on a PCB board with rear electrical connectors, were integrated and tested too, using a special customized bigger flow cell already developed by SYSTEA.

The LFA test unit is a complete CHEMFET LFA bench-top analyser, which will be used to perform automatic measurement, drifts tests, comparisons on single CHEMFET sensors; the internal electronics and software provide directly output data in concentration unit, with the capability to manage the signal acquisition from two CHEMFET sensors, typically to measure NO3- and NH4+.

The measuring unit is fully configurable and open to operator’s modification of the analytical sequence which manages the hydraulic reactor; using the local keyboard and LCD display, as any other standard SYSTEA’s LFA analyser; as an example, it allows:
- To polarize the reference electrode and CHEMFETs drain inputs with single predefined voltages

- To modify any interval time of the analytical sequence which manages the two CHEMFETs measurement.

- To program the opening and closure of any valve included in the loop.

- To turn on or off the peristaltic pump in both versus, at two different speed (low and high).

- To modify the quantity of solutions which can be injected in the loop reactor.

- To perform automatically the standard addition method on each measurement cycle.

The unit is configured to manage n.2 injection valves, to perform:
- Programmable addition of ISA (Ionic Strength Adjuster) stock solution to the sample, before and after the measurement.

- Programmable addition of a stock calibrant solution to the sample, after the sample measurement, to perform “standard addition” method with CHEMFET sensors.

The unit performs after each measurement the automatic calculation of measured concentration; as standard the firmware provides logarithmic calculation, using known addition method, for two CHEMFET chemical sensors choosing between two different algorithms.

Another firmware version is available to perform linear calculation using two standard (low, high), for pH ISFET sensors or CHEMFET sensors, which already includes built-in electronic for linearized standard output.

The calibration is performed using low and high standard solutions, in order to calculate the CHEMFET sensor’s slope by the sequential measure of two external standard solutions (low, high), which have to be always chosen divided by a decade (i.e. low 2ppm, high 20ppm).

The unit is fully programmable to set any configuration parameter (like added standard solution concentration, volume of added standard or Chemfet’s polarization electrical parameters).

The measured data are shown after the end of the measurement using the LCD display and then automatically printed using the printer mounted on the front panel.

Probe demonstrator:
The probe demosntrator is a prototype designed to be specifically deployed in water as a probe.

The analytical part of the device is based upon a novel patented technology named micro Loop Flow Analysis (uLFA); the main characteristics of this new technology is the extreme compactness (the analytical reactor volume is 5 ml only) and the compatibility to be integrated in submergible measuring devices.

The probe is able to mount both types of BSC and FCS CHEMFETs, using the linear modular flow-cell already tested in the measuring stand and in LAAS laboratory.

More information on the Sewing project can be found at:

Informations connexes

Reported by

Systea-Systems Technology Advance
Via Paduni, 2A
03012 Anagni
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