Water level measurement with radar level sensor CR420

Radar water level sensor CR420

The water level radar sensor PARATRONIC CR420 with pulsed radar technology can be set up to carry out a river level measurement. The model presented is the water level radar sensor CR4/20-10.

1- Characteristics of the radar sensor of water level PARATRONIC CR420.

Resolution: Theresolutionof the water level radar sensors CR420 is 1mm for a full scale of 1 to 8m and 2µA for a full scale of 8 to 20m.

Measuring range of the CR420 water level radar sensor: The measuring range or range of theCR420 water level radar sensor CR420 (max. distance between sensor and measured water level) is 10m. It is possible to extend this measuring range to 20m.

Signal type of the CR420 water level radar sensor: TheCR420water level radar sensor CR420 delivers a 4/20mA signal on two wires.

Measuring cone required for the CR420 water level radar sensor: CR420 water level radar sensors emit conical waves. The cone in which the measurement of the water level radar sensor CR420 takes place is extremely small: +/-6°.

Vertical right-of-way of the CR420 water level radar sensor: The vertical right-of-way that cannot be measured corresponds to the height (thickness) of the water level radar sensor CR420 plus the dead zone or blind zone. Concerning the water level radar sensor CR420 this right-of-way is : 23.5cm (8.5cm thick + 15cm blind zone).

Distance station / CR42 0water level radar sensor: the water level radar sensors CR420 deliver a 4/20mA signal on two wires. The maximum distance between the water level radar sensor CR420 and the processing system depends only on the minimum operating voltage of the water level radar sensor CR420 and the supply voltage. As an example, if the station delivers a voltage of 12V= the maximum distance between the water level radar sensor CR420 and the station is more than 2 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 always without degrading the accuracy of the measurement, it is sufficient to increase the supply voltage. The length of screened cable preassembled as standard is 2 m. Water level radar sensors CR420 can optionally be equipped with a longer cable length. In any case, this cable can be extended on site by simply connecting it via a junction box (e.g. with a pre-existing cable on site).

Dimensions and antenna type of the CR420 water level radar sensor : The water level radar sensor CR420 is equipped with a flat solid antenna which gives it reduced dimensions: L: 30cm, W: 22cm, H: 8.5cm.

Colour of the outer housing of the CR420 water level radar sensor: The colour chosen for the standard outer housing of the CR420 water level radar sensor is as neutral as possible in order to ensure optimal discretion of the water level radar sensor CR420 once installed on site. It is a matte green/khaki.

Operating temperature range of the CR420 water level radar sensor: water level radar sensor CR420 is designed to operate in a temperature range from -20°C to +60°C.

Protection rating: The water level radar sensor CR420 is submersible: IP68. This level of protection is achieved thanks to a nitrogen overpressure system.

Frequency used by the water level radar sensor: The water level radar sensor CR420 is a radar specifically designed for outdoor measurement: in accordance with the reference text defining the authorized frequencies for liquid level radar installed outdoors (CEPT/ERC 70-03 Version E), the frequency used by the water level radar sensors CR420 , is 24.125GHz. This document specifies that in France in the 24 GHz range, the authorized emission band is: 24.125 +- 50 MHz. In Europe the band is 24.150 +- 100MHz for a power of 20dBm.

EMC: PARATRONIC's CR420 water level radar sensors comply with the standards EN61000-6-2 - EN61000-6-3 - EN60950-1 and are marked according to the directive 2004/108/CE of the European Parliament and the Council CE.

Resolution:The resolution of the water level radar sensors CR420 is 1mm for a full scale of 1 to 8m and 2µA for a full scale of 8 to 20m.

Temperature drift of the CR420 water level radar sensor:The radar waves are not disturbed by temperature changes. Therefore no temperature drift of the actual measurement is possible. However, the electronics of the 4-20mA signal generation is, like all electronics, subject to small temperature fluctuations.

A temperature measurement of the CR420 water level radar sensor is therefore continuously carried out in order to compensate for possible drifts. The resulting temperature drift is therefore extremely small.

Automatic correction for horizontal errors and maximum angle of the water level radar sensor CR420 with water

The water level radar sensors CR420 automatically correct horizontality errors of plus or minus 10°. This means that a radar level sensor CR420 whose body is mounted at an angle of 10° to the water surface can still carry out correct measurements.

Software for parameter adjustment of the radar level sensor CR420:

No special parameterization software is required. The radar level sensor CR420 can be connected to a 4/20mA input of an acquisition station (e.g. PLC+) without any parameter adjustment in the radar level sensor. The selection of the draught or air draft indication as well as the input of the actual dimension can be carried out directly via the parameter adjustment of the acquisition station.However, if one wishes to check the correct operation of the radar level sensor outside of all connections to a data acquisition unit, or if one envisages the connection to a data acquisition unit which does not allow the standard basic parameter settings of the 4/20mA inputs, it is possible, with the help of a software and a specific interface box of :

* Check the measurement output of the radar level sensor,

* Visualize in the form of a graphical representation the echoes of the radar waves,

* Set the full scale of the CR420 radar level sensor (within the limits of 0-1m to 0-10m for the version CR420/10 or 0-1m to 0-20m for radar level sensors CR420/20 with option 0-20m),

* Choose a signal corresponding to air draft rather than water draft,

* Grab the ladder coast,

* Define the smoothing time (time over which you want to perform a possible average),

* Define the fault delay (time, between 10 and 250 seconds, after which the CR420 water level radar sensor delivers a fault signal if no measurement could be carried out),

* Set the desired fault signal (between 4 and 22 mA).

Possibility to set a smoothing (average at acquisition)

The radar water level sensors CR420 deliver a 4-20mA signal on 2 wires which can correspond either to the instantaneous measurement or to an average of the measurements carried out over a given time. This function can be used to filter out, for example, the effects of waves or wobbling.

Duration of the measurement phase and management of the standby mode

In some cases, in order to optimize the overall power consumption of the site, it is desired that the power supply to the radar water level sensor(s) be "pulsed"; i.e. the CR420 water level radar sensor should be powered only for a few seconds at a regular time step (e.g. 5 seconds every 5 minutes).

The CR420 water level radar sensor therefore works with so-called measuring and standby phases.

* Standby phase of the CR420 water level radar sensor: phase during which the CR420 water level radar sensor is not powered, the duration therefore depends solely on the acquisition time step set in the central unit.

* Measuring phase: phase during which the water level radar sensor CR420 is powered, i.e. phase including both the warm-up time and the actual measuring time. The duration of this phase thus corresponds to the actual heating time to which is added the possible time over which it was decided to smooth (average) the measurements.

The heating time of the water level radar sensor CR420 is only 2 seconds.

Instantaneouspower consumption ofthe CR420 water level radar sensor:

* Standby: 0 mA,

* In measurement: 22 mA for 2 seconds then signal between 4 and 20mA as long as the water level radar sensor CR420 is powered.

As a reminder: the feed time required to obtain a measurement is only 2 seconds + the smoothing time is typically 10 seconds (the smoothing time generally used is between 3 and 13 seconds depending on the site).

Supply voltage of the CR420 water level radar sensor:

In order to be compatible with operation on sites without energy or powered by solar panels and therefore operating on battery voltage, the CR420 radar water level sensors accept supply voltages ranging from 10 to 33Vdc.

Automatic echo filtering and processing of permanent micro level variations

The processing of false echoes is carried out automatically by the CR420 water level radar sensor without special parameter adjustment by automatic use of a special algorithm and elimination of divergent echoes.

Micro-variations are processed by means of a large number of measurements.

Setting and parameterization mode

Since the water radar level sensors CR420 are designed for level measurement on watercourses, no adjustment or parameter adjustment is necessary. The echo processing is fully automatic and the factory parameter adjustment enables direct use on site.

However, a number of specific settings can be made with the help of specific software, especially if a specific use is envisaged.

2- Installation Precautions

Mounting method of the CR420 water level radar sensor and available kits

The water level radar sensor CR420 is mounted directly on a tube with an outer diameter between 30 and 40 mm and approximately horizontal. In addition, an adjustable mounting bracket made of stainless steel allows direct mounting of the CR420 water level radar sensor on a horizontal, vertical or sloping wall.

Special requirements for the installation of the CR420 water level radar sensor,

Since the water radar level sensors CR420 have been developed specifically for measurement on rivers, the installation effort is reduced to a minimum:

* Avoid disturbing objects (reflective surface and orthogonal to the measuring beam) in the measuring cone. of the CR420 water level radar sensor,

* Water radar level sensors CR420 automatically correct horizontality errors of plus or minus 10°. The CR420 water level radar sensor must therefore be mounted approximately horizontally.

Maintenance conditions of the CR420 water level radar sensor

No special maintenance is required for operation of the radar level sensors under normal operating conditions.

Measures taken or to be taken against the attack of lightning or solar radiation

* The radar water level sensors CR420, like all PARATRONIC products, have intrinsically a high level of immunity to overvoltages. However, it is preferable to provide an additional, external lightning protection of type PRO CEM30 .

* No specific protection is to be taken concerning solar radiation:

- Housing of the CR420 water level radar sensor: materials, dyed in the mass, resistant to solar radiation,

- Radar waves: Radar waves are not disturbed by temperature variations,

- Electronics: Any drift in the signal processing electronics is automatically compensated for in temperature.