Sensors compatible with NI 9421

[vsrinivasan]

Hello, 

I am looking to measure RPM of an agitator through a sensor that would be compatible with NI 9421 module for data acquisition. I did a detailed research and  purchased a sensor but unfortunately we are encountering a lot of problems and struggling to troubleshoot. So, I would like to know that if in the past have you heard of any particular sensor for RPM measurement used with NI 9421 module. The current sensor we have is a ROLS-W sensor purchased from Monarch. I can explain the issue if anyone is interested. 

[Carlos_Vaquera]

Hi,

Which is the trouble with the sensor?

IMTC Carlos Vaquera

[vsrinivasan]

The ouput voltage from the sensor when it is not connected to the module is  12V dc (which is equal to the excitation voltage supplied). However, when the NI 9421 module is connected, the voltage output from the sensor drops to 7-8 V dc. This is not sufficient to trigger the module and hence the pulse value displayed is 0 all the time. 

[Carlos_Vaquera]

Hi again,

Ok, could you mention the specs of th power source that you´re using?

IMTC Carlos Vaquera

[vsrinivasan]

The current power supply is a regulated 12vdc power supply rated at max 1A although the sensor itself only requires .13Watts.

[dgriffin91]

Make sure your DC power supply is outputting a constant voltage. This way when you plug in the module the output voltage of the power supply does not change. Also, you could try outputting more voltage from your power supply because the sensor can handle up to 15 Vdc. Therefore when you see the drop in output voltage from the sensor when you plug in the module it might still be high enough to trigger the module. Finally, I would check and see how much current is actually coming out of your power supply. The 9421 module has an input current of ≥3 mA during the ON state. Thus, you want to make sure that the power supply output current is sufficient enough to maintain the 12 Vdc.

[Carlos_Vaquera]

If you are sure that the power source and sensor are ok, I will suggest a conditioning step to solve the problem.

Best regards,

IMTC Carlos Vaquera