US1200, US3200, US4200 ultrasonic level meters

• Measurement of water level and temperature

• Level meter measuring ranges from 0.15 m - 1.2 m (US1200) to 0.35 m - 4.2 m (US4200)

• The digital filter of the measured values of the level height refines the measurement

• Automatic temperature compensation and 1 mm resolution for all types of ultrasonic level meters

• Low current consumption up to 20 mA and first measurement within 2 sec after switching on the power supply (level meters suitable for battery-powered systems)

• S485 and DCL output interface compatible with inputs of recording units M4016, STELA, H1 and H3 (FINET and Modbus RTU protocols)

• High IP67 protection

• Robust stainless steel case

• Adjustable cross in two perpendicular directions for vertical mounting of the level meter above the measured level

• Alternatively, the level meters can be supplied with a radiation cover to reduce the effect of temperature changes on the accuracy of measurement (../RK)

Basic description

Ultrasonic level meters type US1200, US3200 and US4200 are based on the principle of measuring the time delay between the transmitted and received reflected ultrasonic pulse.

Because the speed of sound propagation is temperature dependent, an automatic temperature correction is also performed inside the sensor, which eliminates this measurement error.

Ultrasonic level sensor US1200 (3000) Level meters are supplied in three ranges according to the required measured distance from 1.2 m (US1200) to 4.2 m (US4200). In addition to this maximum distance of the measured obstacle from the level meter (height of the level meter above the minimum level), the so-called dead zone is important for each ultrasonic level meter, which determines the minimum distance of the level meter from the obstacle (height of the level meter above the maximum level). Ultrasonic level meters US1200 are characterized by the value of this parameter only 15 cm.

Digital data transfer from the level meter to the connected recording device allows to transmit more information on one line and therefore each level meter can transmit a secondary quantity in addition to the main measured quantity (level height) and this is the air temperature for USX200 sensors. The transmission of measured values ​​from the level meter to the connected recording unit takes place via the RS485 serial interface in one cable together with a power supply of 10 V to 24 V DC (type 12 V DC).

Use of ultrasonic level meters

Level gauges are suitable for non-contact level measurement in open measuring profiles and watercourses or for level and volume measurement in sumps and tanks. The modified version of the US4200 / RK level meter is also suitable for measuring the height of snow cover.

If the functional or tabular dependence between the level height and the instantaneous flow (consumption equation) is known, it is also possible to continuously calculate the instantaneous flow and the total flowed volume using the connected recording unit type H1, H3, H7, M4016 or STELA. Typical applications are flow meters at the outlet of wastewater treatment plants or limnographic (level meter) stations on rivers.

Mechanical design of level meters

Ultrasonic level meters are often used in climatically unfavorable conditions of sewer manholes and sumps, where the environment is permanently humid. The housing of the level meter is therefore made of stainless steel with a diameter of 50 mm and a length of 110 mm, and the ultrasonic sensor itself as well as the control and evaluation electronics are hermetically encapsulated inside the level meter. This mechanical design eliminates the penetration of water and air humidity into the body of the level meter.

The stainless steel weld-on on the cylindrical body of the level meter serves as a holder for an adjustable cross holder, with the help of which the level meter can be adjusted to a vertical position above the measured water level by means of a spirit level.

The level meter is supplied with a fixed PUR cable, which is used to supply the level meter and to transfer the measured data from the level meter to the connected superior system. The standard cable length is 2 m (other cable lengths can be ordered when ordering the level meter).

Radiation shield

Level gauges marked US1200 / RK to US4200 / RK are intended for accurate level measurements in the outdoor environment not protected from the radiant effects of sunlight. The level meter body is equipped with a robust plastic lamellar radiation cover, which reduces the measurement error caused by the different temperature of the sun-irradiated sensor and the air temperature below the level meter.

Level meters of this type are suitable, for example, for monitoring small river flows or the height of snow cover.

Communication interface of US1X00 level meters

Level meters with the connected recording unit communicate via the RS485 serial interface, which allows to connect more level meters to one unit, if they have set different communication protocol addresses. In addition, the level meter cable also contains a DCL (Digital Current Loop) signal output wire, through which these level meters can be connected to the DAV inputs of the Q2, H3, H7 or M4016 units. The DCL current signal is resistant to ambient interference and can therefore be used to advantage in larger measurement systems (wastewater treatment plants).
In portable devices, ultrasonic level meters are often connected to the recording unit using a detachable connector with high IP67 protection.

Holders for ultrasonic level meters

A number of different stainless steel holders are used to mount ultrasonic level meters above the monitored level. Each holder also includes an adjustment mechanism, with the help of which the level meter can be mounted in the vertical direction so that the ultrasonic signal reflected from the measured level returns to the sensor (variability in two perpendicular directions).

Holders of the DUP1 to DUP9 type, which are sized for Parshall troughs P1 to P9, are intended for very frequent level (and consequently flow) measurements in the Parshall trough.
The cantilever holders DU1-10 to DU1-100 are intended for measurements above the Thomson specific overflow or levels in sumps and tanks. The number of the holder expresses the length of extension of the sensor from the wall.

The DU8-40 (-60, -100) brackets are also boom brackets. However, they are supplemented by a metal radiation cover, which protects the used ultrasonic level meter not only from radiant sunlight but also serves as a mechanical protection of the sensor against vandalism.