Change pressure strain sensor type for SCXI 1314

[catalysthw]

Hi!

 I'd like to ask you how to change strain sensor type.

I'm using SCXI 1314 and one of my pressure sensor is a 4 wires type. (Output 100mV , Excitation: 10Vdc)

,but I want to replace the sensor with another type of current output type. (Output 4~20mV, Excitation: 12-30Vdc)

I checked the connection of voltage output 4 wires. (Set as Full bridge in NI MAX)

Power +  =  Ex+

Power -   =  Ex-

CH+        =  S+

CH-         =  S-

However, I don't know how to connect the 2 wires type with SCXI 1314.  

Also, I don't have enough experience about bridge types( Full, half and quarter bridges)

Can you explain what I should do?

[James_Battleaxe]

Hi,

Could you tell me what sensor you are switching to? I want to make sure your new sensor is still a bridge based sensor. Typically, if that sensor is bridge based and only has 2 wires, it is usually a quarter bridge set up. However, this can be confirmed by referencing the data sheet of the sensor.

After figuring out what kind of bridge completion you need for your sensor, you can set up a task with that sensor in MAX and look in the connection diagram tab to see how to hook up your sensor. I've attached an article at the bottom that shows how to access the connection diagram.

Link: http://www.ni.com/tutorial/5396/en/

[Logan_K]

If you change one unit in your description: 4-20mV --> 4-20mA what you are describing sounds exactly like a current-loop sensor, which typically require a 12 to 30V excitation, and you would need a device that is designed to measure a 4-20mA current output. The SCXI-1520 / 1314 is designed for bridge sensors, so this won't work.

Here is a description of the type of sensor that I assume you are describing: https://en.wikipedia.org/wiki/Current_loop

[catalysthw]

Thank you so much.

Switching to mV output pressure transducer, Omega PX 215.

PX215-060AI

Output 4-20mA

Excitation: 24 Vdc (12~36 Vdc)

Range:  0~60 psi   (Absolute pressure range)

Omega PX 215-060AI,   http://www.omega.com/manuals/manualpdf/M2165.pdf, http://www.omega.com/Pressure/pdf/PX205.pdf

Previous pressure transducer which was installed.

PX 212-100GV

Output +- 100mV

Excitation 10 Vdc , Max 15 Vdc

Range: 0~100 psi  (Gage pressure range)

Omega PX 212,   http://www.omega.com/manuals/manualpdf/M2165.pdf,  http://www.omega.com/Pressure/pdf/PX202.pdf 

Could you let me know how I can deal with the excitation difference and output?

[catalysthw]

Thank you so much!

Is there alternative ways to use the sensor with SCXI 1314?

I have a complicated VI to control several parameters and the sensor I want to switch is one of parts in the VI.

So I need to check the way to use a new one with SCXI 1314.

How can I use current-loop sensor?

[Henrik_Volkers · Accepted solution]

One thing you migth try is to put a 5 Ohm resistor in the current loop. that will result in a 100mV voltage drop over the resistor , however check the ground conditions.  Since you will need a new sensor sensitivty calculation anyway you can use a 4.7 Ohm resistor or use 2 10Ohm in parallel ....   just find a good match between input voltage range of your 1314 and the 4-20mA.

And you will need an external powersupply for the sensor.