Measurement + instrumentation: Products + services
Monitoring analogue process values
Everywhere in industry, electronic sensors are used to detect process values such as temperature, pressure or flow. Process value monitoring oen takes place directly in the sensor. However, sometimes separate monitoring devices are required – for example, if two measured values are to be o set against each other and the resulting value is to be monitored. Evaluating measured values The evaluation unit from ifm, which is designed for monitoring, analysis and o setting two process values, is ideal for determining di erential values in pressure, flow, level or temperature. It has various operating modes and two analogue sensors can be connected to the unit. This means two switching points can be assigned to a measured signal, or a limit value can be assigned to two measured values. The two measured signals can be scaled and linked with each other using mathematical functions such as addition or subtraction. The process value calculated in this way can be monitored with up to two switching points and can be output as an analogue signal (4...20 mA). Measured values can be transmitted digitally to a higher-level controller via IO-Link. The device’s extensive parameter setting is
also conveniently carried out via IO-Link. A clearly visible OLED display shows the values and parameter settings. Application cases As an example, in an ap- plication case providing for dierential pressure measurement on filters in an industrial plant, two
The ifm evaluation unit can be used to determine differential values in pressure, flow, level or temperature.
pressure sensors measure the pressure before and aer the filter. If the filter becomes clogged over time, the di erential pressure increases. In another application case, the ifm evaluation unit is used to monitor pressure measurement in a fermentation tank. In addition to the hydrostatic pressure at the bottom of the tank, the pressure of the gas above the medium, which increases as a result of fermentation, is measured. This measure is subtracted from the hydrostatic pressure to determine the level.
For more information visit: http://www.ifm.com
Keeping solar panels clean
els can be rectified in good time,” says Grobler. The MDFS is compact, lightweight and easy to install. It can be used in two ways. In Basic Mode, when manually comparing the clean and dirty cell readings, the operator can decide when cleaning is needed. In this mode, the control box is not required. In Advanced Mode, with the optional control box, the system automatically calculates the soiling attenuation rate (%) of the PV panels. This value can be used directly to decide if cleaning is necessary and to provide confirmation when cleaning and other maintenance tasks have been performed. The MDFS system provides five data channels: sun elevation, clean solar cell rad, dirty solar cell rad, MDFS status and attenuation. Both the MDFS2 and MDFS2-S o er a measurement range of 0 to 1400 W/m 2 , operating in temperatures from -20 o C to + 60 o C and warning, pairing instruction via digital outputs. The MDFS2 o ers a measurement error of +-2.1% and the MDFS2-S a +-2.2% measurement error. The Data Acquisition System (DAS) model METEODATA-4000 collects the solar radiation gathered by the clean and dirty reference cells and additional information regarding tasks performed at the field monitored by the control box. This data is used in the calculation of attenuation due to soiling. The data collected by the DAS is recorded in a SQL Server installed in a Data Collection Centre, where it is accessible to be displayed and exported to Excel files. “The MDFS is a welcome addition to the Senseca product range of environmental monitoring instrumentation. It will assist in ensuring PV farms and large commercial solar panel installations are always running optimally,” says Grobler.
Keeping solar panels clean is an important factor in ensuring they function e ectively. Dust, dirt and other debris can block the sunlight that solar panels use to deliver power. Dirty solar panels can lead to a reduction in performance of up to 25% and accumulated dust can potentially cause hot spots that damage cells. To assist in the quick monitoring of solar panels for dirt, Senseca has introduced a Dust Fall Monitoring System (MDFS). Used at solar photovoltaic farms and other commercial installations, it is designed to alert control centre operators at photovoltaic solar farms when the panels need to be cleaned. “The MDFS can easily be added to the solar panel control system,” says Jan Grobler, Managing Director of Senseca South Africa. “It compares the radiation collected by two-compensated reference cells with outputs either in voltage (Model MDFS2) or Modbus protocol (Model MDFS2-S). One cell (the clean cell) must
always be kept clean, and the other cell selected to be monitored by the system (the dirty cell) is cleaned at the same time as the PV panels. “The device en- ables quick iden- tification of dirty solar panels so any drop in the perfor- mance of the pan-
The MDFS is designed to assist in keeping solar panels clean, free of dust and debris.
For more information visit: www.senseca.com
MARCH 2026 Electricity + Control
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