DAQmx scales, MAX 4.3.0f0, NI-DAqmx 8.6.1, AI channels on DAQPAD-6015 saturate at ~5 V, not 10 V, Why?

[Victr]

Hello;

I have LV 8.2, with Measurement and Automation (MAX) 4.3.040.  Last week I uninstalled  Ni-DAQmx 8.6.0f12, and installed the recommended NIDAQmx 8.6.1.

I created new singleNIDAQmx Task in MAX which contained,  3 DIFFerential channels and 2 NRSE channel. In the Voltage Input Setting, the  voltage range is set to 10 V to - 10 V, Continous samples 6 S/sec. As mentioned above ther terminal config is either DIFFerential or NRSE.

In MAX I created DAQmx Scales, using a linear scale for the 3 DIFF channels.

When I measure the DIFFerential channels, which each has ~250 Ohm resistor, the Fluke Voltmeter meters displays correctly voltages up to 9.5 V.

When I run my code with the MAX-DAQmx Task-> Configuration -> Voltage Input Settings -> Custom Scale -> No Scale... SAVE the lvm file display the correct raw voltage values. That is values above 5 Volt, but below 10 V.

But, running the code from Custom Scale -> No scale  to a "user created DAQmx Scalings", the lvm file display INCORRECT voltage values. That is, the voltages are clamped at 5 Vs, but the Fluke DVM and MAX channel Test Panels  read between 5 V and 10 V. 

Where else do I need to set the max and mix voltage values for each DAQmx channel?

[mallorim]

Hi Victr,

I would make sure that each channel set up has the range of 10 V to -10V. The default setting in MAX is 5 to -5 V and if you added the channels before making the voltage adjustment, some of the ranges might still be set to a max of 5 V.

Some questions:

Can I ask what the linear scale you are using is? If you remove every channel but one from the task and then apply the scale, do you see the same problem?

Is it all five channels that rail at 5 V or only one?

Also, how are you saving your data to an lvm file? Are you running the task in MAX or using the task constant to run it in LabVIEW and then save the data to a file?

Regards, Mallori M.

[victorvilla93]

Good Morning;

The problem is solved.

I did create a new single channel DAQmx task, create a new lDAQmx inear scale  (48x - 37 , where x is the input differential voltage) , used the test panels, set the Voltage Input scaling from 10 to -10 V Volts to 10 to -10 Celsius. The same problem of clamping occured. Data ranged from 60 to 302 Celsius (that is,  5 volts differential on DAQPAD 6015). The channel has a 250 Ohm resistor across the differential terminals..

When I replaced the MAX -> Config _> Voltage Input Setting -> 10 to -10 Celsius TO THE CORRECT RANGE of 50  to 400 Celsius. My write to measurement file data looked correct. Data ranged from 50 to 4xx Celsius.

I did not notice the problem since the output should have clamped at 10 Celsius from Voltage Input Settings, not 302 C. My question is why did the scaled value not clamp at 10 C?

Thank you for your time.  Victor