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Hi all. For a few years, I have been using the HSC frequency measurement on the V350. My program uses the example that was given by Unitronics and I have not altered it much. Suddenly, my programs have stopped working when I download them to a new PLC. The HSC behaves unusual and gives me false readings. My program is to control micro water turbines and it uses HSC to measure the frequency of the generator. I am using a simple frequency converter that gives me pulses into my HSCO port. The pulses are 50Hz and I confirm using a digital meter that the input receives 50Hz. In the hardware setting, I define my input in the HSI(RELOAD) tap that my counter target value is 50 and I enable Reload on startup (See Hardware setup in attachment). Now in the ladder program, I define the "Frequency Measurement based on HSC" function block as shown in the picture. When I run the program on my V350 I receive signal to my input and the actual HSC value is incrementing. I can see the number goes 50 steps for about 1 second so it's counting right (50Hz gives 50 pulses). But my frequency seems to be off from the function block. See this video: https://streamable.com/ovzps I measure about 62.11Hz with the function block. The status message for the Frequency block jumps between 0 and 16. Zero means normal behavior but there's no explanation on what 16 means in the manual. Now if I change the Permissible delta (C-in the function block) to RAW measurement and start it again, this happens: https://streamable.com/tbt24 The counter slows down (lags) and I measure about 10Hz, and that makes no sense. Should I not receive about 50.00Hz? out of the function block? I tried to change PLC, tested on SAMBA and I am experiencing the same thing. What am I missing. The only thing that has changed (I think) is that I updated the Visilogic software and the firmware on the PLC. A test program is at the bottom if you want to see it for your self. Thank you Cheers, Arnor HSC_Test.vlp