Typical technical data hydrostatic sensors CNR :The hydrostatic sensors CNR are submersible transmitters of piezo-resistive technology for monitoring and measuring, in differential pressure, of stable or moving liquid levels.
The measuring range or full scale (height of water for which the hydrostatic sensor gives 20mA) is definable between 0 to 30cm of water and 0 to 30m of water.
The non-deterioration range is 1.5 times full scale.
The accuracy of the measurement given by the hydrostatic sensors CNR does not depend on the rate of change of the level or the distance between the station 
and the hydrostatic sensor. These parameters have no influence on the accuracy of the measurement.
The accuracy of a hydrostatic sensor can be broken down into three distinct elements:
Temperature drift: variation of the signal according to the variation of the river water temperature (for a constant water level).
Sensitivity: smallest variation in level detected by the hydrostatic sensor,
Linearity: accuracy of the sensor as a function of the water level,
Although a temperature sensor is integrated in the hydrostatic sensor CNR allowing continuous temperature compensation, the temperature drift is not completely zero. Temperature drift of a hydrostatic sensor CNR 10m: +/- 0.025% of full scale per °C deviation from the set temperature.
Worst possible temperature drift for a hydrostatic sensor CNR measuring range other than 10m: 0.025% of full scale per °C deviation from the set temperature.
Sensitivity of a hydrostatic probe CNR 10m: +/-0.05% of full scale, i.e. 5 mm
Worst possible sensitivity for a hydrostatic probe CNR with a measuring range other than 10m: +/-0.1% of full scale.
Linearity of a hydrostatic probe CNR 10m: +/-0.04% of full scale.
Worst linearity possible for a hydrostatic probe CNR with a measuring range other than 10m: +/-0.25% of full scale.
- Distance station / hydrostatic sensor :The hydrostatic sensors CNR deliver a 4/20mA signal on two wires. Consequently, the signal transport distance has no influence on the accuracy of the measurement or on the wear and tear of the parts, or even on the current consumed by the sensor.
The maximum distance between the hydrostatic sensor and the data acquisition unit does not depend on the hydrostatic sensor but on the supply voltage. As an example, if the station delivers a voltage of 12V the maximum distance is more than 3 km and if the station delivers a voltage of 24V the maximum distance is more than 12 km.
For distances greater than 12 km, and still without degrading the accuracy of the measurement, simply increase the supply voltage.
The hydrostatic sensors CNR deliver a 4/20mA signal on two wires.
The hydrostatic sensors CNR have a diameter of 21mm.
In order to avoid measurement drift in case of eddies, the sensors must be of a weight suitable for the application.
hydrostatic probe CNR: weight 250 g (+50 g / meter of cable)
The body of the hydrostatic sensors CNR is made of STAINLESS STEEL 316L.
- Compliance with health standards :"Any operator called upon to intervene in the construction of fixed installations for the production, treatment and distribution of water intended for human consumption must ensure from his suppliers, by any appropriate means, that the materials or objects delivered to him comply with the provisions of this Order". (Order of 29 May 1997 on materials and objects used in fixed installations for the production, treatment and distribution of water intended for human consumption [O.J. n° 126 of 1 June 1997 page 8675 - Art. 3] ).
"In order to help manufacturers build up and obtain proof of the sanitary conformity of their products, in 1999 the health authorities developed the system of the sanitary conformity attestation (ACS). This system makes it possible to assess the suitability of a product to come into contact with water intended for human consumption, in the light of the provisions of the decree of 29 May 1997, as amended". (Notice to persons responsible for placing on the market materials and objects coming into contact with water intended for human consumption, excluding natural mineral water, used in water production, treatment and distribution installations [J.O n° 248 of 23 October 2004 page 17971] ).
Since the entry into force of the above-mentioned texts, operators working on drinking water production, treatment or distribution installations require, when purchasing hydrostatic level sensors, the supply of equipment with a Health Conformity Certificate issued by an approved laboratory.
These attestations have been defined by the health authorities to constitute the proof of conformity of industrial products. The tests carried out to issue these certificates make it possible to assess the suitability of a product to come into contact with water intended for human consumption, in the light of the provisions of the Order of 29 May 1997 as amended.
Although, in accordance with this order, any operator called upon to intervene in the construction of fixed water production, treatment and distribution installations must have proof of the sanitary conformity of their products, very few manufacturers are concerned about the safety of their products. In order to provide a "commercial" response to their customers, these unscrupulous suppliers indicate that they use cables or materials known as "food grade". This mention, which is subject to compliance with criteria much less drastic than the ACS, does not in any way demonstrate the suitability of a product to come into contact with drinking water.
The hydrostatic sensors PARATRONIC are not only in conformity with the standards in force but are, concerning the standards EMC higher than the minimum required by these standards.
The hydrostatic sensors CNR operate regardless of the loop supply voltage between 6Vdc and 38Vdc.
The hydrostatic sensors PARATRONIC are all protected against the reversals of polarity.
The hydrostatic sensors CNR work for the measurement of liquids with a temperature between -20°C and +50°C.
Before use: -20ºC / +80°C (0ºC / +80°C after use).
- Cable and venting on the hydrostatic sensor CNR:The structure of the cable, the dimensional, mechanical and chemical characteristics of the elements the component melts part of the technologies resulting from the experiment and the capacities of research and development of PARATRONIC. This element is one of the know-how property of PARATRONIC and counts for much in the differentiation of the hydrostatic sensors PARATRONIC compared to the other hydrostatic sensors present on the market.
The cable used for the hydrostatic sensors CNR allows the hydrostatic sensor to be brought to atmospheric pressure without using a capillary, thus avoiding the inconvenience of crushing, pinching, bending or clogging (by a drop of water) of the said capillary.
In addition, the flexibility of the cable allows for installations with bends, angles and tortuous runs.
The hydrostatic sensors CNR and MPXF of PARATRONIC are guaranteed including risk of lightning, without the need to install any external protection system. This feature is the result of 20 years of experience and research and development in this field. This know-how counts for much in the differentiation of the hydrostatic sensors PARATRONIC compared to the other hydrostatic sensors present on the market. Indeed, the hydrostatic sensors CNR and MPXF of PARATRONIC supports without damage the overvoltages of atmospheric origin of intensity 20kA, that these overvoltages are conveyed by the cable or that they result from a shock in the ground whose distribution of the potentials would come to touch the hydrostatic sensor.
This technology has three major advantages:
- It is much more effective than the simple installation of a surge arrester because the latter protects, in the best case, only against surges carried by the cable.
- It avoids the cost of wiring and connection and the periodic checking of the good condition of a lightning arrester,
- It is effective whatever the conditions of installation; for example, a lightning arrester only plays its role correctly if its earth cable is short, which is impossible in the case of a tower tank.
The desired cable length will be specified when ordering, it can vary from 1 to 300ml. Any order for a hydrostatic sensor with more than 300m of cable may result in standard delivery times being exceeded.
The cable is usually fixed using the cable clamp supplied with each hydrostatic probe.
The cable has no specific connector which makes it compatible with most stations on the market.
The hydrostatic sensors CNR and MPXF all incorporate a galvanic separator. This allows direct cabling on acquisition or remote transmission equipment (the use of galvanicseparator is generally recommended by manufacturers).
The hydrostatic sensors CNR are completely removable, allowing the cable to be changed without changing the sensor, the modification of the full scale of the hydrostatic probe or any repair, calibration or re-calibration intervention.
The hydrostatic sensors CNR deliver a 4/20mA signal on two wires permanently as long as the loop is powered. The measurement "cycle" therefore corresponds to the acquisition time step set in the acquisition unit or the PLC.
The standby is therefore carried out by the acquisition station or the PLC when it stops supplying power to the measuring loop.
The time required to establish the measurement by the hydrostatic sensor CNR is 50 milliseconds.
The hydrostatic sensor is woken up by the acquisition station or the PLC when it feeds the measuring loop again.
The hydrostatic sensors CNR deliver a 4/20mA signal on two wires, so their consumption depends exclusively on two parameters :
- The water level at the time of measurement: for a 30m full scale probe: for 0m the instantaneous consumption is 4mA, for 15m it is 12mA, for 30m it is 20mA.
- The time during which the measuring loop is powered by the acquisition station. The hydrostatic probes CNR do not need to be powered for more than 50 milliseconds.
For the consumption calculations below, we will consider the following elements:
- A water level located on average at mid-scale, i.e. 15m, therefore an instantaneous consumption of 12mA
- A loop feed time of 1 second and not 50 milliseconds since most stations and PLCs on the market cannot generate power for less than 1 second.
- the consumption between 2 measurement cycles is zero.
Consumption in case of a measurement every 5 minutes with stand-by mode without taking a measurement:
Measuring time: 12 x 1 second = 12 seconds
Standby time: 12 x 299 seconds = 3588 seconds
Consumption during one hour = [(12 x 12mA) + ( 3588 x 0mA) / 3600 = 0,04 mAh
Consumption for 24 hours = 24 x 0.04 = 0.96 mAh
Consumption in case of measurement every 15 minutes with standby mode when no measurement is taken:
Measuring time: 4 x 1 second = 4 seconds
Standby time: 4 x 899 seconds = 3596 seconds
Consumption during one hour = [(4 x 12mA) + ( 3596 x 0mA) / 3600 = 0.013 mAh
Consumption during 24 hours = 24 x 0.013 = 0.32 mAh
Consumption in case of permanent measurement :
Measuring time: 3600 seconds
Standby time: 0 seconds
Consumption during one hour = [(3600 x 12mA) + ( 0 x 0mA) / 3600 = 12 mAh
The hydrostatic sensors CNR deliver a 4/20mA signal on two wires directly proportional to the measured water level. All the treatments and filtering with respect to micro variations are thus carried out by the acquisition unit in the form, for example, of averages during acquisition.
The hydrostatic sensors CNR do not require any adjustments or settings other than those made at the factory.
Since the hydrostatic sensors CNR deliver a 4/20mA signal on 2 wires, the parameter setting of the control unit or the PLC corresponds to the parameter setting of a 4/20mA input.
In drinking water: No special maintenance is required for the use of hydrostatic sensors CNR.
In sanitation: Several thousands of hydrostatic sensors CNR are currently in place in sewage treatment plants or wastewater lifting stations with a high load of sand, grease, sludge and aggressive products. Under these extreme conditions, maintenance is limited to flushing the sensor approximately once a year.
Preventive replacement of parts: Since the hydrostatic sensors CNR and MPXF have no wearing parts, except for the measuring cell, whose replacement requires factory intervention for reasons of calibration, calibration and sealing, no preventive replacement of parts is necessary.
Particular points to watch: the only point to watch is that the cable, in its immersed part, has not been damaged or punctured.
The installation requirements for hydrostatic probes CNR are four :
The cable of the hydrostatic sensor, used for the setting at atmospheric pressure, without capillary, it is necessary to take care that its end (connection to the data acquisition unit, to the PLC or to a connecting cable) is out of water and that in the case of junction box, this one is not of the "resin casting" type.
As the hydrostatic sensor cable is used for atmospheric pressure, without capillary, care must be taken not to injure it when it is installed.
In order to protect the hydrostatic sensor and its cable from moving or floating elements (lift station or river), it is advisable to install the hydrostatic sensor in a stainless steel or plastic protective tube (avoid galvanized steel).
The hydrostatic probe must be submerged without resting on the bottom of the watercourse, station or borehole. In fact, a distance of about 5 to 10 cm between the bottom of the hydrostatic sensor and the bottom of the structure makes it possible to avoid possible fouling phenomena related to the silting of the site.
The characteristics described are subject to change without notice by the manufacturer.
Please refer to the technical documentation: Documentations
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