Each of our flow devices is manufactured at our site in Wülfrath, Germany and 100% tested for quality and function before we send it to you. This ensures that you can start using the device smoothly from day 1. From over 30 years of experience, however, we have learned that questions rarely arise during commissioning. We have touched on the most common questions as well as measures to resolve them here.

Question A: Why doesn't my device work?

The most common cause is that the device has been connected to no or the wrong supply voltage. Therefore, we recommend checking the supply voltage and correct wiring. If everything is correct, the green LED of the device should light up when voltage is applied.

Question B: Why does the device not measure flow although flow is present and the green LED is lit?

The cause of this error may be that the flow is outside the measuring range or that the installation position of the sensor is not optimal. To check the former for airflow sensors, we recommend removing the sensor and blowing hard on the sensor elements; this should trigger the sensor. Sensors for use in water should trigger if the switch point is set to minimum flow and the hexagon of the sensor is enclosed in a fist and the thumb is pressed from above onto the sensor tip. If the sensor responds to this function test, it is functional.

If, however, the flow measurement fails, we recommend checking the installation position of the sensor. The inlet and outlet distances specified in the operating instructions must be adhered to. In addition, for airflow measurements the sensor length should be selected so that the sensor projects into the middle of the duct for small pipe diameters and into the outer third of the duct for diameters from approx. 120 mm, as this is where the flow can be measured most accurately. When installed, the sensor must be aligned in such a way that the gaseous medium flows fully through the cross-hole and the marking on the sensor tube points in the direction of air flow. Flow sensors for water must be installed so that the sensor is immersed in the liquid medium up to the beginning of the thread. 

If these conditions are met, the next step is to check the model-specific setting parameters. If, for example, your unit has a start-up bypass or the possibility to adjust the sensitivity, we recommend checking their correct setting and, for example, setting the sensitivity to maximum via the potentiometer.

Question C: Why is flow measured even though there is no flow?

Due to the sensitivity of our devices, they react to even the smallest flow velocities. Some of our customers have noticed in the past that there is flow in their systems even when they are at a standstill, e.g. due to a ventilation flap through which fresh air enters from outside.

To test your sensor for correct function, we therefore recommend removing the sensor and fully enclosing it with your hand to shut off any draught. If the sensor no longer shows any flow, simply adjust the switching point accordingly.

Another cause for flow being indicated although none is present can be a sudden rise in temperature that exceeds the temperature gradient of the unit and thus causes the temperature compensation to overshoot for a short time. This can be prevented by setting the switching point after the maximum medium temperature has been reached.

Question D: Special case devices for ATEX areas - why does my unit not work?

The most frequent cause of malfunctions when commissioning our ATEX certified units is incorrect wiring of the Zener barriers, as the two Zener barriers supplied by us have different values for current and voltage. Please identify the Zener barrier types by the imprint on their housing and make sure that the sensor, evaluation unit and Zener barriers have been connected in accordance with the wiring diagram in the operating instructions, otherwise measurement errors may occur.

Question E: Special case RLSW8AL[...] - why does my device not detect flow?

Please note that each unit of the type RLSW8AL[...] with remote sensor is calibrated to one specific sensor. If you are using several units of this type, please check the labels on the sides of the evaluation units and sensors to ensure that the correct sensor is connected to the corresponding unit, otherwise measurement errors will occur.

When using the 4 mA ... 20 mA output, please also make sure that terminals 2 and 5 have not been bridged. If this is the case, disconnect the connection between terminal 2 and 5 and restart the unit by cutting the power supply and reconnecting it.

Please note that the 0 ... 10 V output is a three-wire connection and the 4 ... 20 mA output is a four-wire connection.

If the measured value of your unit exceeds 100%, readjust the measuring range so that 100% is displayed at maximum flow rate. Please note that the measuring range must be adjusted separately for each measuring unit (l/min; m/s; cbm/h) according to the procedure described in the operating instructions.

In case of further problems, please contact us and, if possible, have the version number displayed during start-up and the error code displayed ready.