han_5583

QUOTE (mross @ Jul 16 2008, 02:17 PM)

You can use a counter to measure the time period between pulses. There are examples on how to do period measurement with counters.

OR

You can acquire the analog voltage and measure the time between the pulses the sensor produces. This is normal data acquisition and you should first consider a buffered acquisition not continuous. You can repeat the buffered acquisitions to produce a quasi continuous output of RPM.

The conversion from time in milliseconds to RPM is fairly simple.

(X milliseconds / time between falling signals) * (1 minute / 60 000 milliseconds) * [(time /rev) / (time between rising signals)] =

X minutes / rev

1/X = RPM

If you use the counter method the falling edges are much less prone to noise problems.

Mike

Hi Mike,

Thanks for your advice. Actually I do plan to use the analog voltage, but I'm not sure my DAQ (USB-6008) is a buffered DAQ. Do you have any example on how to use the input voltage for the counter? I was hoping to measure how many pulse within a minute but I'm not sure how to do that.

Thanks in advance

Hi All,

Currently I'm doing a project on RPM sensor connecting to Labview. My RPM sensor uses IR transmitter/receiver. When the motor turns in front of the IR transmitter receiver, the IR light will be reflected back and the circuit will have an increase of voltage from 1.8V to 3.2V. I'm planning to connect this output voltage to the Labview via the digital input, but I'm having problem as how to do the programming in Labview to calculate the rpm of the motor.

Appreciate if anybody can help me on this.

Thanks

Amy Tan

this was what i have done.

Hi guys, I'm a moderate labview user and I have done a few project before. My current project is about generating PWM signals to control the rpm of an electric motor. When I simulate the signal I can see the generated PWM clearly on the virtual graph, but when I connect it with the DAQ assistant (analog output), the PWM signals suddenly run very slow. I suspect I dont provide enough buffer to the output, but I dont know how to increase the buffer size. Currently the PWM signals does not go through the DAQ device. Anyway, I'm using USB-6008. Please advice.