LabVIEW
Show C Series input module value on waveform.
Solved!
Hi Zohaib,
at ±10V measurement range and 12bit resolution the LSB is equivalent to ~5mV.
For measuring voltage across a PT100 it's a rather bad option, as 5mV relate to a dT of 12K…
@ZohaibRamzane wrote:
If it is,which resolution will be good for measuring +-10V including low voltage as +-50mV.
You can calculate this on your own - based on your accuracy requirements!
An easy (but dirty) fix would be to use a somewhat larger current of 2mA or 3mA, which would also double (or triple) the voltage across the Pt100 resistor…
Or use an amplifier with a simple OpAmp.
Or use a ready-to-use signal converter, converting your Pt100 signal into an induxtry standard signal of ±10V - perfectly suitable for your NI9201 module…
Hi Zohaib,
@ZohaibRamzane wrote:I need as accurate measurement as possible.
When you want to measure Pt100 sensors then you should use either NI9216 or NI9217…
@ZohaibRamzane wrote:
As you said, 5mV resolution we can get with 12 bit. It means we can measure a change of 5 mV reliability. Why it is bad for pt100? Why it can not measure less voltage say 100mV accurately.
The NI9201 gives measurement data according to its datasheet. Did you read the datasheet? There are numbers for accuracy, repeatability, and so on…
Hi Zohaib,
your NI9201 can measure values of 100mV or 110mV. It can even measure 0mV or ~5mV…
The point is: even though it can measure those values it cannot measure values in between. And due to noise and other problems it might even not accurately measure those signal values - as is described in the datasheet.
@ZohaibRamzane wrote:
But i am specifically looking for reason why 12 bit module is not able to measure small voltage like 100 or 110mV as i have to tell my Professor before purchasing another one.
Can you give me that reason so that i can be sure.
Again I have to repeat: read the datasheet of the NI9201. Print it out for discussion with your professor, mark the most critical specifications and tell your professor about them (and why they prohibit more accurate measurements)!
Hi Zohaib,
at ±500mV and 16bit resolution you get ~15µV/bit. This might be not accurate enough for thermocouples, especially those containing Pt. There are special modules for TC measurement (for a reason)!
And you forgot the CJC needed for thermocouples. I guess that was already mentioned in one of your long threads about temperature measurement. What kind of background knowledge do you have on electrical measurements? What kind of backgorund on measurements at all? What kind of student are you being not able to get the basics in all the time you are discussing this in the LabVIEW forum?
Hi Zohaib,
@ZohaibRamzane wrote:
It is working perfectly. But since voltage measurement are very low say 0.11V or 0.12V if i set excitation current 1 mA. Similarly for 2mA, Voltage measured is 0.22 or 0.23V. When i plot this reading values, I got waveform like this as per pic attached.
Those voltages are just as expected. The only "very low" in this setup is the "very low specifications" of the DAQ module that you use! Use a better DAQ module when you want more accurate measurement values…
@ZohaibRamzane wrote:
I want waveform to be smooth. Should i do averaging over array values to avoid this or else is there another way to do so.
You might apply a filter. Averaging array values is just a low-pass filter. LabVIEW also provides other filter functions as well…
On the image of your VI:
Why do you need a SharedVariable to transfer data between loops?
Why do you create an array from that scalar "AI0" measurement value before writing into the SharedVariable?
Why do you need to Reshape that array in the consumer loop to a 2D array? You still only have exactly one (1) sampe in this array!
What's the point of that sequence structure?
Why don't you use AutoCleanup (before posting code images)?
Again:
Did you notice those "Training resources" in the header of the LabVIEW board? Did you take them? (You really should…)
