Python:DAQ 2

This page contains pictures and graphs related to DAQ 2 for EGR 103. It has been updated for Fall 2019 and nidaqmx.

Notes

• As before, if the system seems to not recognize Dev1, try Dev2 instead.

Channel 0 Failure

A few boards seemed to have a failed Channel 0; you can still do the lab with the following modifications:

Hardware

The measurement wires will need to be changed as follows: $$\begin{array}{cccc} Purple & Pin B7 & Line 33 & ACH1\\ Yellow & Pin Y5 & Line 66 & ACH9\\ Blue & Pin C7 & Line 65 & ACH2\\ Orange & Pin H7 & Line 31 & ACH10\\ Green & Pin I7 & Line 30 & ACH3\\ Brown & Pin Y3 & Line 63 & ACH11 \end{array}$$

Software

For a single measurement, change the end of line 22 to from ai0 to ai1; for multiple measurements, change the end of line 22 from ai0:2 to ai1:3

Pauses

There are input commands in the code which will cause the program to wait for an input - specifically when the program first runs to check the lights. You will need to hit return to un-pause the program. The way to see if the program is paused is to look in the console to see if it is waiting for an input.

Resource Reserved / Task Cannot Start

If you get an error that a resources is reserved or that a task can't start, clear all the variables and re-run the script. Clearing the variables should clear all reservations to the DAQ card. If that does not work, try restarting the kernal.

Typographical Errors

• Before section 2.5, you may need to install nidaqmx on the DAQ computer. To do that:
  • Go to the Start menu and find the Anaconda3 folder
  • Start the Anaconda Prompt
  • In the Anaconda Prompt, type

pip install nidaqmx

• If it asks you if that is OK - it is

Circuits

• aio_output
• aio_meas1
• aio_meas3 and aio_get_data

Graph from aio_meas1

Graph showing single measurement when the overall voltage is calculated with:

    v_out = 2.5 + 2.5 * np.sin(6 * np.pi * k / N)

That is,

\( \begin{align} V_{out}=2.5+2.5\sin\left(\frac{6\pi k}{N}\right) \end{align} \)

Graph from aio_meas3

Graph showing all three measurements when the overall voltage is calculated with:

    v_out = 2.5 + 2.5 * np.sin(6 * np.pi * k / N)

Graph from aio_get_data

Graph showing all three measurements when the overall voltage is calculated with:

    v_out = 5 * (k / (N - 1))

assuming N = 300. Note at the far left that they all start at either exactly 0 V!

Codes

Here are the codes references in the assignment. Note that the extra blank spaces are in earlier programs to make room for the code added to later programs. For the second and later codes, the lines that were added or changed from the script listed immediately above it will be indicated with yellow highlighting.

aio_output

 1 # %% Import modules
 2 import numpy as np
 3 import time
 4 import nidaqmx as daq
 5 
 6 
 7 # %% Create a task
 8 taskout = daq.Task()
 9 
10 
11 # %% Add analog output lines
12 taskout.ao_channels.add_ao_voltage_chan("Dev1/ao0")
13 
14 
15 
16 
17 # %% Check lights
18 taskout.write(5)
19 input("PAUSED - Hit return to continue ")
20 taskout.write(0)
21 
22 # %% Write values to output
23 N = 300
24 
25 for k in range(300):
26     v_out = 2.5 + 2.5 * np.sin(6 * np.pi * k / N)
27     taskout.write(v_out)
28     time.sleep(0.01)
29 
30 
31 # %% Turn all off when finished and close task
32 taskout.write(0)
33 taskout.close()

aio_meas1

 1 # %% Import modules
 2 import numpy as np
 3 import time
 4 import nidaqmx as daq
 5 import matplotlib.pyplot as plt
 6 
 7 # %% Create a task
 8 taskout = daq.Task()
 9 taskin = daq.Task()
10 
11 # %% Add analog output lines
12 taskout.ao_channels.add_ao_voltage_chan("Dev1/ao0")
13 
14 # %% Add analog input lines
15 taskin.ai_channels.add_ai_voltage_chan("Dev1/ai0")
16 
17 # %% Check lights
18 taskout.write(5)
19 input("PAUSED - Hit return to continue ")
20 taskout.write(0)
21 
22 # %% Write and read values
23 N = 300
24 meas = np.zeros((N, 1))
25 
26 for k in range(N):
27     v_out = 2.5 + 2.5 * np.sin(6 * np.pi * k / N)
28     taskout.write(v_out)
29     time.sleep(0.01)
30     meas[k] = taskin.read()
31 
32 # %% Turn all off when finished and close task
33 taskout.write(0)
34 taskout.close()
35 taskin.close()
36 
37 # %% Make plots
38 fig, ax = plt.subplots(num=1, clear=True)
39 total = meas[:, 0]
40 ax.plot(total, "r")

aio_meas3

 1 # %% Import modules
 2 import numpy as np
 3 import time
 4 import nidaqmx as daq
 5 import matplotlib.pyplot as plt
 6 
 7 # %% Create a task
 8 taskout = daq.Task()
 9 taskin = daq.Task()
10 
11 # %% Add analog output lines
12 taskout.ao_channels.add_ao_voltage_chan("Dev1/ao0")
13 
14 # %% Add analog input lines
15 taskin.ai_channels.add_ai_voltage_chan("Dev1/ai0:2")
16 
17 # %% Check lights
18 taskout.write(5)
19 input("PAUSED - Hit return to continue ")
20 taskout.write(0)
21 
22 # %% Write and read values
23 N = 300
24 meas = np.zeros((N, 3))
25 
26 for k in range(N):
27     v_out = 2.5 + 2.5 * np.sin(6 * np.pi * k / N)
28     taskout.write(v_out)
29     time.sleep(0.01)
30     meas[k, :] = taskin.read()
31 
32 # %% Turn all off when finished and close task
33 taskout.write(0)
34 taskout.close()
35 taskin.close()
36 
37 # %% Make plots
38 fig, ax = plt.subplots(num=1, clear=True)
39 total = meas[:, 0]
40 resv = meas[:, 1]
41 ledv = meas[:, 2]
42 ax.plot(total, "m-", resv, "b-.", ledv, "g:")
43 ax.legend(["$v_s$", "$v_R$", "$v_{LED}$"])

aio_get_data

 1 # %% Import modules
 2 import numpy as np
 3 import time
 4 import nidaqmx as daq
 5 import matplotlib.pyplot as plt
 6 
 7 # %% Create a task
 8 taskout = daq.Task()
 9 taskin = daq.Task()
10 
11 # %% Add analog output lines
12 taskout.ao_channels.add_ao_voltage_chan("Dev1/ao0")
13 
14 # %% Add analog input lines
15 taskin.ai_channels.add_ai_voltage_chan("Dev1/ai0:2")
16 
17 # %% Check lights
18 taskout.write(5)
19 input("PAUSED - Hit return to continue ")
20 taskout.write(0)
21 
22 # %% Write and read values
23 N = 300
24 meas = np.zeros((N, 3))
25 
26 for k in range(N):
27     v_out = 5 * (k / (N - 1))
28     taskout.write(v_out)
29     time.sleep(0.01)
30     meas[k, :] = taskin.read()
31 
32 # %% Turn all off when finished and close task
33 taskout.write(0)
34 taskout.close()
35 taskin.close()
36 
37 # %% Make plots
38 fig, ax = plt.subplots(num=1, clear=True)
39 total = meas[:, 0]
40 resv = meas[:, 1]
41 ledv = meas[:, 2]
42 ax.plot(total, "m-", resv, "b-.", ledv, "g--")
43 ax.legend(["$v_s$", "$v_R$", "$v_{LED}$"])
44 
45 # %% Save values and figure
46 color = input("Color: ")
47 eval("ax.set_title('{:s}')".format(color))
48 fid = eval("open('{:s}_data.dat', 'w')".format(color))
49 for k in range(300):
50     fid.write("{:.4e} {:.4e} {:.4e}\n".format(*meas[k, :]))
51 fid.close()
52 eval("fig.savefig('{:s}_plot.png')".format(color))

Questions

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