How do I get the 1121 card to read the switch and make it a 1 or 0 to count pulses?

Question

Hello,
I am developing a test stand to test tires. We have LabView 7.1 and the SCXI chassis with an 1121 transducer card. I am trying to count the rate and total number of revolutions made by the tire. The signal is acquired from a 12V-proximity switch that is actuated once per RPM. The tire turns at 1,000 RPM or a little more.
The signal will have to go through a 100-foot cable to get to the LabView chassis, will this be a problem?
How do I get the 1121 card to read the switch and make it a 1 or 0 to count pulses?
Will LabView be able to read this many pulses per second?
How do I get MPH and a RPM reading out of it?
Thank you,
James Happe

Answer 1

Hi James,
Since you are cabling your DAQ board to an SCXI chassis with an 1121, you will not be able to use your counters without additional hardware.
The 1121 is an analog input signal conditioning module. It performs filtering and attenuation to help measure analog signals. What it does not have is access to your board's counter pins.
In order to use your counter pins you will need to get the necessary hardware. You have two options:
1) Buy and SCB-68. This is a breakout box that will cable directly to your DAQ board replacing your SCXI chassis. You can connect your signals directly to your counter with this. However, I would advise against this because your application has a 12 volt signal. This will overload the 5v maximum voltage for your counter pins.
2) Buy a 1180 feedthrough panel. This will allow you to use all of your DAQ board's functions with the SCXI chassis. Withouth the 1180 feedthrough panel, the SCXI-1121 is the only thing connected to your DAQ board. Since the 1121 only performs conditioning on the analog inputs, that is all you can access. The other pins cannot be used (no access). With the 1180 feedthrough panel, you can put a connector block on and access all of your other pins (including the counter pins). Again, I would advise against this since your 12 volt signal will overload your counter pins.
My suggestion would be to perform an analog input task. Set up your 1121 in MAX and use a LabVIEW shipping example. In the shipping example select an analog input channel from your SCXI-1121 module. Set the appropriate voltage range and take some measurements. Once your signal is connected and you can read it using an analog input example you are half way there.
Take the analog input shipping example and modify it to perform frequency analysis on the voltage readings. You can simply wire the data from the DAQmxRead VI into one of the frequency analysis VI's (noted in my first post). The output if that VI will give you the frequency of your signal.
-Sal