Why do the specifications for the High-sensitivity 61F Floatless Level Controller say, "possible to use with 15 kOHM or less, however, this may cause reset failure"?
The interelectrode voltage of 61F is AC. This generates a floating capacitance between ground and the cable that connects the electrode bar to 61F body. The current that flows due to this cable-to-ground floating capacitance causes the reset failure.
The reset current for 61F High-sensitivity Controller is 0.05 mA AC min. If the current flowing through the ground capacity is, for example, 0.1 mA, there will be a reset failure because of the reset current (0.05 mA AC min.) even when there is no liquid between the electrodes.
1.Shorten the cable between the Electrode and 61F Controller. (For the 61F-GP-N8 High-sensitivity Controller, use a 0.75-mm2, 3-conductor, cabtyre cable that is 50 m or less in length.)
2.Use a General-purpose Controller for applications where the liquid resistance can be detected at ordinary sensitivity (0 to 4 kOHM).