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?
Material: Stainless Steel
Protection Rank: IP67
Output Signal: 240-30ohms
Resolution Range: 10-40mm
Operational Temperature: -40°F ~ +185°F (-40℃ ~ +85℃)
Solved! Go to 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.
After a closer look into the 4300C spec .. input impedance is 92 Ohm,
so the supply voltage should be ~2,3 V.
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> )