NI 9218 Excitation

[linu95k]

I have a few doubts regarding NI 9218 Universal Analog Input module, 

The NI 9218 module has external supply pins Vsup and Comm for 9-30V and the specification sheet mentions that the module is cable of providing 2V, 3.3V and 12V excitation.

I have the following doubts:

1. The Vsup is required to be connected only to use 12V excitation which is not available for Bridge connections.

2. If I want to use bridge connection the module can only produce an output of 2V & 3.3V based on the type of Load connected, for this I don't require Vsup connections?

3. The Excitation Voltage is selectable but in bridge mode will only allow values 2V & 3.3V or is it auto-determined based on the Load connected?

4. The Manual mentions 2V for >120Ohm and 3.3V for >350Ohm, in this case it suggested load (120 or 350Ohm) is actually one arm of the bridge right?

5. What is the purpose of Shunt Caliberation and how to use it?

I have piezoresistive pressure transducer refer to link below:

https://download.keller-druck.com/api/download/PKbqU3rcUzDLSNsehdzNee/en/2019-11.pdfhttps://keller-d...

for which I am not sure on how to connect it to NI 9218, can someone please help

[GerdW]

Hi linu,

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@linu95k wrote:

1. The Vsup is required to be connected only to use 12V excitation which is not available for Bridge connections.

2. If I want to use bridge connection the module can only produce an output of 2V & 3.3V based on the type of Load connected, for this I don't require Vsup connections?

3. The Excitation Voltage is selectable but in bridge mode will only allow values 2V & 3.3V or is it auto-determined based on the Load connected?

4. The Manual mentions 2V for >120Ohm and 3.3V for >350Ohm, in this case it suggested load (120 or 350Ohm) is actually one arm of the bridge right?

5. What is the purpose of Shunt Caliberation and how to use it?

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1. As described here the Vsup is only used for 12V sensor excitation in ±16V mode.
2. The GettingStarted (from item 1) doesn't mention any external power supply in bridge mode, so you don't need it.
3. When excitation is selecteable then it's up to you to set the correct value.
4. For a full-bridge the total resistance across the bridge is the same as the resistance of one resistor: Ohm's law combined with Kirchhoff's rules!
5. There are sources that explain that, one of them is this…

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@linu95k wrote:

I have piezoresistive pressure transducer refer to link below:

https://download.keller-druck.com/api/download/PKbqU3rcUzDLSNsehdzNee/en/2019-11.pdfhttps://keller-d...

for which I am not sure on how to connect it to NI 9218, can someone please help

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There's a schematic in the datasheet, with 2 "INs" and 2 "OUTs". Shouldn't be so hard to connect…