Why it shows“Not all channels support on-demand operations. Only clocked operations are allowed”when I use NI-DAQ to acquire data?

Hi, all,

When I want to use MATLAB (R2022b-academic use) to control NI-USB 4431 to acquire data, the command window shows "Not all channels support on-demand operations. Only clocked operations are allowed." What does this mean? I can't figure out how to solve it (I have installed NI-DAQmx toolbox, version 22.2.0). Here is the code:

dq = daq("ni");
dq.Rate = 8000;
ch1 = addinput(dq, d.DeviceID, "ai1", "Voltage");
tabledata = read(dq)

In addition, the NI-4431 device information is as follows.

ni: National Instruments(TM) USB-4431 (Device ID: 'Dev1')

Analog input supports:

-10 to +10 Volts range

Rates from 1000.0 to 102400.0 scansc

4 channels ('ai0','ai1','ai2','ai3')

'Voltage','Accelerometer','Microphone','IEPE' measurement types

Analog output supports:

-3.5 to +3.5 Volts range

Rates from 800.0 to 96000.0 scansc

1 channel ('ao0')

'Voltage' measurement type

Thanks!

Answer 1

[Manikanta Aditya]

Hi Hunag,

As per my understanding, you are getting error saying ‘Not all channels support on-demand operations. Only clocked operations are allowed.’ When trying to use NI-DAQ to acquire data.

The specific input channel you are trying to use does not support on-demand operations, which is when data is acquired on demand as opposed to at a regular interval. Instead, it only supports clocked operations, which require you to specify a regular clock signal to trigger data acquisition.

As a workaround, you can add a clock signal to your data acquisition session by using the "addclock" function.

dq = daq("ni");
dq.Rate = 8000;
ch1 = addinput(dq,"Dev1","ai1","Voltage");
clock = addclock(dq,"ScanClock","ai1",dq.Rate);
start(dq,"Duration",1);
tabledata = read(dq)

For further reference, please check out this link to know more about ‘addclock’ function:

• https://www.mathworks.com/help/daq/daq.interfaces.dataacquisition.addclock.html

I hope this resolves the issue you are facing.

[KOLBY]

Hello,

I am facing a similar issue when using a MCC USB 205 DAQ board. I receive "Added channel does not support clocked sampling: clocked operations are disabled. Only on-demand operations are allowed. " after adding an output channel. Additionally, this sets the Rate of the board to 0, preventing me from implementing a clock.

While this is the opposite warning, do you know how to use simultaneous analog input and output given the error received?

Is this a limitation of the board, or is there a workaround in MATLAB?

Thank you,

KS

Code used to troubleshoot, error follows that readwrite is limited to clocked operations.

clear; clc; close all;
d = daq("mcc")
addoutput(d, "Board1","ao1","Voltage");
d
addinput(d, "Board1","ai0","Voltage");
d
% clock = addclock(d,"ScanClock","Board1/ai0",d.Rate);
outScanData = linspace(0,1,d.Rate)'; % Increase output voltage with each scan.
inScanData = readwrite(d,linspace(0,1,d.Rate)');