Choosing Modules Based on Excitation for Pressure Transducers

Updated May 14, 2018

Reported In

Hardware

  • NI-9219
  • NI-9237
  • NI-9263

Issue Details

  • I have a third party device, such as a pressure transducer, that has a certain excitation voltage.  How do I narrow down what are best modules for me to use?
  • How do I power my pressure transducers?

Solution

Excitation voltage is the operating voltage of a device, which means that the device needs a certain amount of voltage to be activated (i.e. if the excitation voltage is 10 V, it would need a minimum of 10 V to be able to function).
  1. Consult the spec sheet of your transducer to find out the power requirements or required excitation voltage.
  2. Consult the spec sheet of the input module that you are looking to use to find out the provided excitation voltage. The excitation provided may change based on how you have the card configured, such as bridge configuration settings. If your excitation voltage provided by the module is lower than the excitation expected by your transducer, your transducer will not function properly.
  3. If your input module cannot supply the needed voltage to your device:
    1. Look at other available C Series input modules that supply excitation. Some C Series modules are available for specific sensor types, such as strain gauges, thermal sensors, or IEPE sensors. Look at modules specific to your application, or, if you don't see one that will suit your application, consider a universal analog input module.
    2. Look at C Series output modules that can supply the needed power to your device
    3. Consider using an external power supply

Additional Information

Example:
  • Third party pressure transducer is a Omega PX26-030DV
    • This has an excitation voltage of 10 Vdc
  • Module that we are looking at is the NI-9219 which is an Analog Input Module
    • For full-bridge devices it has an excitation of 2.7 V
Based on that information, 2.7 V is not enough for the pressure transducer. Therefore we have 2 different options:
  1. We use the NI-9219 for taking in the signal for analysis and get an Analog Output Module, such as the NI-9263, or a power supply to get the excitation voltage of 10 V for the pressure transducer
  2. National Instruments have Strain/Bridge Input Module, such as the NI-9237, that support 10 V excitation signal. However, more information is needed to understand how many channels (or how many sensors) can be used on the module
    • You would need to know the load resistance of the transducer to calculate how much power (P = V^2/R) is needed to run 1 sensor. Sometimes, even if it's a 4 channel module, we may only be able use 1 channel because of the power the sensor uses.

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