Level sensors are widely used in various industries to determine the level in tanks, for example, the food and beverage industry. It is also essential for crop protection: the elobau level sensor has been playing an important role here for a number of years.
One company that uses level sensors from elobau in their application is the Hol & Son Company based in Meteren, a small village in the ‘Betuwe’ that supplies highly advanced fruit crop protection systems all over the world.
Hol Spraying Systems
The company was founded by great-grandfather H. Hol in 1933 as a blacksmith and gradually grew into an agricultural machine repair shop. Grandson and great-grandson Hol started a separate branch developing agricultural machinery. “About ten years ago we started developing crop protection machines for fruit growing,” says great-grandson, Hendrik Hol. “We mainly focus on orchard sprayers that can drive through the rows of fruit trees. They can spray one to three rows at a time. The installations are pulled by a tractor.” In 2010, it became a separate, independent company under the name Hol Spraying Systems (H.S.S.). The company is growing so fast that it will move to a new location next year (2020).
Easy operation of the spraying system
The spraying system consists of a tank which has an integrated elobau digital level sensor that is connected to a PLC or PCB. The liquid often consists of 98% water and an additional 2% in powder form. The level sensor detects the liquid level and the temperature in the tank. The data is transferred to the H.S.S. Controlbox via a specially designed touchscreen that can be hung in the tractor. This allows the driver to the status of the irrigation, such as the level of liquid in the tank or the total amount of liquid sprayed, at a glance from the driver’s seat. “That is very important nowadays because you have to keep records of how many chemicals have been sprayed onto the land due to laws and regulations, and that is very easy with this system,” says Hol.
A special option for installation with the PCB is GPS control. Every tree has a GPS position, and the installation will only start spraying if it detects a tree. If no leaves are detected the watering system stops. This is an especially useful option if you have very large crop plots, such as in Canada or New Zealand.
Configure the level sensor according to your requirements
To measure the level of liquids in tanks, the level sensor uses reed contact technology with a rotatable, programmable head. It is a hollow, stainless steel rod, in which there is an elongated printed circuit board (PCB) with reed contacts on it, for example, every 10 mm. The length of the bar can be customised to each customer’s requirements. There is a float on the outside of the rod that moves up and down with the level of the liquid. A magnet is contained in the float, which activates the reed contacts as it moves up and down, causing a change in the 4-20mA analogue measurement signal. This analogue measurement signal is then converted in the PLC (or PCB) to the tank content that is displayed on the screen to the operator. The elobau level sensors can be customised as required from various options for process connection, length of the measuring area, grid distance (distance between the reed contacts), float material, connection form with for example AMP plug, M12, or fixed cable.
Best value for money
In the past, Hol Spraying Systems used other options for level measurement such as pressure sensors and ultrasonics, but in the end, they opted for the elobau level sensor.
“We have compared the price/quality of various meters, and elobau was the best. In 2012, we introduced the digital measurement of the liquid level, and we have used the elobau sensors for about three years now,” said Hol.
Hol is very satisfied with the sensor. It is accurate: the deviation is up to around five liters on a full spray tank. Before the introduction of the digital measurement, this was done with transparent hoses, and the deviation could amount to around thirty to forty liters! They are also easy to assemble.
In the meantime, H.S.S. has customers all over the world, and their fruit crop protection systems with the elobau level meters are used from America to New Zealand.