08-02-2013 04:07 PM
I have a pressure transducer which outputs current signal. I want to connect it to NI 9205 module to collect the signal. I already have a NI 9944 resistor to
transfer current signal to voltage signal. Could you tell me how to connect the transducer, resistor and the Module 9205?
Solved! Go to Solution.
08-02-2013 04:38 PM - edited 08-02-2013 04:38 PM
Hi beechmont,
it seems the NI9944 is made to use with a NI9237 module...
- You need to supply your transducer. See it's manual on specifications for supply voltage.
- You connect transducer output to COM and ai0 input of NI9205 IN PARALLEL to a shunt resistor of your own.
- I suggest to use resistors in the 400Ohms range to use the 10V range atmost while still allowing over-current situations (some transducers output upto 22mA)!
08-02-2013 07:04 PM
@beechmont wrote:
Could you tell me how to connect the transducer, resistor and the Module 9205?
You can go through these links below, which demonstrate how to connect, sensor (transmitting current signal) to a DAQ device:
1. Measuring and Generating Current
2. Measuring Current with an Analog Voltage Input
3. Fundamentals, System Design, and Setup for the 4 to 20 mA Current Loop
08-05-2013 07:53 AM
Could you send me a link of shunt resistor ? Thanks!
08-05-2013 08:00 AM
Hi beechmont,
look into an electronics store near by you, or use a web-based distributor of electronic parts. Most of them have big catalogues with several pages listing resistors for all kind of applications, like here...
You have to define more than just the resistance, so search on your own!
08-05-2013 09:56 AM
To elaborate on what GerdW is saying, you can measure the voltage drop accross a known resistance. The resistor you choose will be such that the current from your transducer will result in a voltage drop you can measure (say 5 or 10 V for the maximum pressure you can read). The reason he suggested around 400 Ohm is that you want you reference resistor to be much lower than the imput impedence of your DAQ device to maintain accuracy. The actual value will vary so make sure to measure the resistor you get, and make sure it's power rating (1/4 W or 1/2 W, etc.) is sufficient for the current you are using. Using a resistor with too small of a power rating can result in excessive heating which changes the resistance, and therefore introduces error.
08-05-2013 10:15 AM
Thanks a lot! Can I buy the shunt resistor in the local store, like Radioshack, homedepot?
08-05-2013 12:12 PM
shunt resistor is just a general term. A resistor can be purchased with an extremely wide variety of resistances and power loads and can be made from a wide variety of materials. Radioshack MAY carry some resistors (the radioshack near me seems to just sell phones now). A hobby shop is another option. But in all honesty, you can buy a resistor online for a few cents (check out Digikey or AlliedElectronics).
The important thing is that YOU need to know which resistor to buy.
08-05-2013 05:17 PM
http://www.wika.us/upload/DS_PE_S_10_en_us_16325.pdf
Please check the above link for the specfication of my transducer. It seems that power supply of transducer should be 14~30 V. Now I have a NI PS-15 Power Supply which supplies 24~28 v. Could you tell me what resistor can be used in my case?
I found this in Radishack. Please check it. http://www.radioshack.com/product/index.jsp?productId=12554531&filterName=Type&filterValue=3-watt+r...
Thanks!
08-06-2013 02:10 AM - edited 08-06-2013 02:12 AM
Hi beechmont,
see page 4 of the transducer manual: use "3 wire system" and replace the ampmeter shown by your shunt. Measure the voltage over the resistor...
I still suggest to use ~400Ohm instead of 500Ohm, for reasons see above!