Level Sensor Output Signal: 240-30Ω, Is it possible to measure with PXIe 4300?

[JJ@TH]

I'm going to buy NI PXIe 4300 with TB4300C for measuring current from many sensors.

One of the sensors has the level sensor that has 240-30 Ω output. I don't want to buy the DMM module.

Is it possible to use PXIe 4300 with TB4300C or TB4300?

Specifications:
Model: 878640
Material: Stainless Steel
Length: 550mm
Protection Rank: IP67
Output Signal: 240-30ohms
Resolution Range: 10-40mm
Operational Temperature: -40°F ~ +185°F (-40℃ ~ +85℃)

[Henrik_Volkers · Accepted solution]

At least a link to the datasheet of that sensor would be helpful 😉

What accuracy is needed?

IF that sensor resistor can carry ~20mA current, the easy way would be to add a constant 1.5V supply and use your current measurement. The current sensing resistor of the 4300C is 50Ohm (as far as I found the rigth spec) , so sensor and card input in series to a 1.5V source will give you a current range of 20mA (1.5V/(25Ohm+50Ohm) ) to ~5mA (1.5/(250+50)) .

Senorvalues with a little extention 😉

If you can 'steal' 3.3V- 5V (30mA .. again some buffer)  somewhere in your PXI chassis,  a low drop voltage regulator to 1.5V will do the job. If more accuracy is needed and you are not shure about the stability of your 1.5V source: Measure it 🙂  another current channel and a stable 25Ohm Resistor (4 times a 100Ohm?) and a source supplying 40mA (+buffer) .. voila 😄

An other (more common) method: Use 'any' available AC or DC voltage source and a known reference resistor and spend two voltage input channels. Build a voltage divider with the two resistors (known and sensor) and measure the voltage across them.  

If the voltage source is known, only one voltage measurement is needed. 

[Henrik_Volkers]

After a closer look into the 4300C spec .. input impedance is 92 Ohm,

so the supply voltage should be ~2,3 V.  

[JJ@TH]

Thank you for your suggestion Henrik.

Here are the details in the pdf I got from the website
https://goo.gl/9fPjnL

I don't need high accuracy +- 10 to 20 Ω is fine.

[Henrik_Volkers]

Output .. :WTF is Standard American  240-33 ohms ??  😄

Migth work as  suggested with a 2.3V supply

The very simple version is a 5V supply and  a 150 Ohm , your sensor and the 20mA current input as a serial chain.

Still should show the discrete sensor values ...

The measured current is I= <Your voltage supply voltage> / (92 + <Sensor resistance>+<additional series resistor> )

[JJ@TH]

I think I will use voltage divider.

Thank you.