问National Instrument Long Monitoring Python

EN

# This works for a NI9234 card
import nidaqmx
from nidaqmx.constants import AcquisitionType
from nidaqmx import stream_readers
import numpy as np
import csv
import time
from datetime import datetime

sample_rate = 2048                              # Usually sample rate goes 2048 Hz, 2560 Hz, 3200 Hz, 5120 Hz, 6400 Hz (at least for a NI9234 card) 
samples_to_acq = 2048                           # At least for vibration matters, Samples to acq go from 2048, 4096, 8192
wait_time = samples_to_acq/sample_rate          # Data Acquisition Time in s, very important for the NI task function, and since we have 2048 on both sides, time is 1 s
cont_mode = AcquisitionType.CONTINUOUS              # There is also FINITE for sporadic measurements
iterations = 10
    
with nidaqmx.Task() as task:
    now = datetime.now()
    military = now.strftime('%H:%M:%S')     # Just recording the time like 20:32:54 instead of 8:32:54 pm
    first_header = ['Some title in here']
    second_header = [f'T. Captura: {military}']

# Create accelerometer channel and configure sample clock. current_excit_val=0.002 enables IEPE, velocity measured in ips and accel in m/s2, 
# both prox and tachometer can be used with a simple voltage channel.
# For more info about channels: https://nidaqmx-python.readthedocs.io/en/latest/ai_channel_collection.html

# Two accelerometer channels
task.ai_channels.add_ai_accel_chan(physical_channel = "cDAQ9181-1E3866DMod1/ai0", sensitivity = 100, current_excit_val = 0.002)
task.ai_channels.add_ai_accel_chan(physical_channel = "cDAQ9181-1E3866DMod1/ai1", sensitivity = 100, current_excit_val = 0.002)

# Two voltage channels
task.ai_channels.add_ai_voltage_chan(physical_channel = "cDAQ9181-1E3866DMod1/ai2")
task.ai_channels.add_ai_voltage_chan(physical_channel = "cDAQ9181-1E3866DMod1/ai3")

total_wait_time = wait_time * iterations                         # We will only take 10 measurements, 10 s for this example
samples_to_acq_new = samples_to_acq * iterations                 # Also multiply by 10 to keep the same ratio, it should be 

# Sets source of sample clock, its rate, and number of samples to aquire = buffer size
task.timing.cfg_samp_clk_timing(sample_rate, sample_mode = cont_mode, samps_per_chan = samples_to_acq_new)               
  
start = time.time()
print ('Starting task...')         # Just to keep a control in your console

# Saving the 4 channels to a csv file. This file is overwritten everytime the program is executed.
# It should appear in the same folder that your program is located. 
with open('data_10times.csv', 'w', newline = '') as f:
    writer = csv.writer(f)
    writer.writerow(first_header)
    writer.writerow(second_header)
    
    # adding some blank spaces in btw
    writer.writerow('')
    writer.writerow('')        
    
    x = np.linspace(0, total_wait_time, samples_to_acq_new)       # Your x axis (ms), starts from 0, final time is total_wait_time, equally divided by the number of samples you'll capture
    
    data = np.ndarray((4, samples_to_acq_new), dtype = np.float64)  #Creates an array, 4 columns each one of 20480 rows
    nidaqmx.stream_readers.AnalogMultiChannelReader(task.in_stream).read_many_sample(data, samples_to_acq_new, timeout = 14) # it should't take that long for this example, check out time for other exercises               
    
    for value in range(len(x)):
        writer.writerow([x[value], data[0][value], data[1][value], data[2][value], data[3][value]])

elapsed_time = (time.time() - start)
print (f'done in {elapsed_time}')