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I am having trouble reading data from a pressure sensor using MATLAB. The pressure sensor is connected to an NI 9219 Analog Input Device. Firstly, i tested the device to make sure it is working using NI DAQmx (Measurement and Automation Explorer) software and below is a waveform of an output received : Pressure Sensor Response in DAQmx software So i have tried a couple of things based on comments below, i have done 2 runs of the code changing only the addAnalogInputChannel settings:

1) First Run is using Voltage in the addAnalogInputChannel, i have attached a picture of my workspace and Waveform below: Workspace for Voltage Voltage Waveform

2) Second Run is using Bridge in the addAnalogInputChannel, i have attached a picture of my workspace and Waveform below:

Bridge Code Bridge Waveform

My previous code is shown below:

%% NI UST-9162 Interface %%
devices = daq.getDevices;
% disp(devices) %Identify devices (NI USB-9162 as 'Dev1')
s = daq.createSession('ni');
ch0 = addAnalogInputChannel(s,'Dev1','ai0','Current'); %Honeywell pressure sensor

%ch0.BridgeMode = 'Full'; %Configures the bridge mode property of Honeywell
%ch0.NominalBridgeResistance = 5000; %Honeywell datasheet suggests 5 kOhm

ch.Coupling = 'DC';
ch.ADCTimingMode = 'HighSpeed';
ch.ExcitationVoltage = 2.5;
s.Rate = 2; %Scan rate per second
s.DurationInSeconds = 2; %Set data collection for S seconds
[data,time] = s.startForeground; %Start test data collection

%% Plot Captured Data %%
figure(1)
clf(figure(1))
grid on

plot(time,data,'-.','linewidth',2)
xlabel('Time (s)')
ylabel('Voltage')
legend('Honeywell')
xlim([0 s.DurationInSeconds])
ylim([-0.03 0.03])

I have listed the equipment below with links to datasheet:

1) Pressure Sensor(Mine is Port Type B with 6G)

2) NI-9219 Analog Input Module

3) MATLAB 2017b with Data Acquisition Tool Box

4) NI DAQmx

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  • \$\begingroup\$ Hook up a known voltage to the DAQ, then poll it from matlab, if your not getting anything then look at the software until you do. \$\endgroup\$ – Voltage Spike Oct 2 at 21:13
  • \$\begingroup\$ If i understand stand your response correctly, the first waveform does show a response in DAQ but does not show response in MATLAB, the settings for both are exactly the same \$\endgroup\$ – sk95 Oct 2 at 21:33
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It looks to me like your Y-axis on "the waveform" is kind of ambiguous (what are the units of "Amplitude")? If I look at the numbers on that axis closely, it goes from 0 to 1.65 milli-something.

Your MATLAB plot has a Y-axis of labeled "Voltage" and the scale goes from -30 milli-Volts to +30 milli-Volts. The "flat" line may just be an artifact of being "too zoomed out" on the Y-axis to see variation. Can't you print out the data vector in MATLAB (sorry, it's been a while) rather than insisting on the Plot to convey information to you, just for the purposes of debug?

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  • \$\begingroup\$ i have edited my post with workspace and added more waveforms that are zoomed in , i believe my problem lies in not being able to use the following commands in my code as MATLAB gives me error when i try to set them : ch.Coupling = 'DC'; ch.ADCTimingMode = 'HighSpeed'; ch.ExcitationVoltage = 2.5; \$\endgroup\$ – sk95 Oct 3 at 19:06
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I had to call the tech support at mathworks and it turns out that at this point in time the library does not support NI-USB-9162 interface with the NI-9219 which is causing errors in reading data and setting parameters which is a development issue and the team is currently working on a solution and they will contact me if the problem is fixed.

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