Why do my input initialize the correct voltage, then accumulate to 10V

We're seeing a different value in Matlab than we are in DAQami.

My versions:

Windows 10

Instacal 6.60

Matlab 2024a

Data Acquisition Toolbox Support Package for Measurement Computing Hardware 24.1

We expect about 6 V and 0.5-0.9 Volts

DAQami (native MCC software) is reading thosevalues correctly, but MATLAB when using slightly modified script of the example script at https://www.mathworks.com/help/daq/getting-started-with-session-based-interface-using-mcc-devices.html

we get these followings results where it starts at the correct values but then increases immediately to 10 V for both input channels. See attached graph.

%% Discover Available Devices

% Discover devices connected to your system using |daqlist|. To learn more

% about an individual device, access the entry in the device table.

d = daqlist("mcc");

d(1, :)

%% Create a DataAcquisition

% The |daq| function creates a DataAcquisition object. The DataAcquisition

% contains information describing hardware, scan rate, and other properties

% associated with the acquisition.

dq = daq("mcc")

%% Add an Analog Input Channel

% The |addinput| function attaches an input channel to the DataAcquisition.

% You can add more than one channel to a DataAcquisition.

addinput(dq, "Board0", "Ai5", "Voltage");

addinput(dq, "Board0", "Ai6", "Voltage");

dq

%% Change Default Properties of the Acquisition

% By default, acquisitions run for one second at 1000 scans per second. To

% acquire at a different rate, change the |Rate| property.

dq.Rate = 100;

%%

% Run the acquisition and plot the acquired data:

[data, startTime] = read(dq, seconds(3));

hold on;

plot(data.Time, data.Board0_Ai5);

plot(data.Time, data.Board0_Ai6);

hold off;

xlabel("Time (s)");

ylabel("Voltage (V)");

Answer 1

[Divyam]

Hi @Ian,

It may happen that while using the Data Acquisition Toolbox Support Package for your hardware, the signal is running into an overrange condition. To avoid this issue, you can set up the "Range" and "TerminalConfig" of the input channels.

ch1 = addinput(dq, "Board0", "Ai5", "Voltage");
ch1.Range = [5.5 6.5];
ch1.TerminalConfig = "SingleEnded"
ch2 = addinput(dq, "Board0", "Ai6", "Voltage");
ch2.Range = [0.5 0.9];
ch2.TerminalConfig = "SingleEnded"

To learn more about the "Range" and "TerminalConfig" properties for input channels, refer to this documentation: https://www.mathworks.com/help/daq/channel-properties.html