Connecting String Pots

[askhassan]

I have 10 String Potentiometers and 2 Linear Potentiometers that I need to connect to one of NI Modules (in differential connection). Which Module should I use ? and how many channels should it have ?

I have cDAQ Chassis (8-slot) 9178. I also have NI 9216 which I don't know if it could do the job or not.

I appreciate any help on this, Its my first time to deal with DAQ systems.

Thanks in Advance

Ahmad

[rolfk]

String Potentiometers is a very vague thing. They could have many different types of outputs.

- resistive potentiometer (simply a normal potentiometer)

- 0-10V analog output

- 0 (4) - 20 mA output

- Incremental Encoder output

- Absolute Encoder output

- digital communication interface like RS-232, USB, CAN,, DeviceNet or even Ethernet

depending on what type of String Potentiometers you have you may need VERY different IO modules to connect to them.

With the linear potentiometer I assume you mean a standard resisitive potentiometer.

[askhassan]

I mean the one attached below. I have an NI 9205 but I need to figure out the connection to the terminals also I don't know if the NI 9205 power is enough or I will need a DC power supply source.

Thank you 

[rolfk]

The NI 9205 does not provide power but rather consumes power from the chassis it is in. It has differential inputs and a virtual ground AI Sense for pseudodifferential inputs and a real ground. You will of course have to power your passive resistor sensors externally for them to work.

The 2 outer ends need to be connected to the power supply and middle tap to the AI input. Depending on the mode you use your module in you also will want to connect the ground of your power supply to AI- (differential mode), AI Sense (pseudodifferential mode), or Ground (single-ended mode).

[askhassan]

Thank you for your clarification that was really helpful. For my case I have 10 string pots the pot out put of each one will go to A different AI+ In the pinout and the two end terminals for each one will share a connection with the +ve and -ve terminals of the power supply ? Also for the ground of power supply would have to go for each AI- separately?

Thank you so much !

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@rolfk wrote:

The NI 9205 does not provide power but rather consumes power from the chassis it is in. It has differential inputs and a virtual ground AI Sense for pseudodifferential inputs and a real ground. You will of course have to power your passive resistor sensors externally for them to work.

The 2 outer ends need to be connected to the power supply and middle tap to the AI input. Depending on the mode you use your module in you also will want to connect the ground of your power supply to AI- (differential mode), AI Sense (pseudodifferential mode), or Ground (single-ended mode).

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[askhassan]

I am currently connecting the 16 differential inputs in the 9205, the first 8 are working well but the other 8 are not, is there anything related to wiring the COM to something? right now I have the bottom 4 spring terminals empty without any connections (COM, DO0, PFI0 and AISENSE)

[OxSanj]

Hello,

I have a similar SP2 Draw wire potentiometer with a max 24-30V DC external power source along with NI-9234, and NI-9237 modules in hand. Not sure how the Potentiometer which will serve as a displacement transducer can be connected to one of these modules.  The NI-9234 has BNC connectors while NI-9237 has a RJ50 NI-9945 adaptor.