Flexlogger Calculate RPM with an Analogue input module and a Voltage Pulse

[James4832]

Hi there, I have a need to get RPM from a 1 pulse per revolution signal, but i only have analogue input modules available to use (I am using 4 slots in my chassis, and only have a free channel on a NI9203 or 3 x NI 9230). I understand this involves finding the rising edges over time, however I cannot seem to find how to do that with the NI9203 or NI 9230 modules. Is there a way i can do this with a math channel or similar? 

[Darylld]

Hi,

The NI 9203 and NI 9230 modules do not support digital edge counting (detecting rising edges) since both of these modules have only analog inputs. However, as you had mentioned, we can simply configure a few calculation channels for this task.

You can first try creating a math channel to detect the rising edge of the analog input voltage using a threshold such as analog_input > 2.5  which will return a boolean high. This can then be used to create another math channel which will calculate the time of this boolean high event occuring (timeDiff). and finally another math channel can be created to calculate the rpm using the formula RPM = 60 / timeDiff

Please revert back if this works.

Thank you

Thank you