I am using the nidaqmx library in python. When I attempt to read the voltage from 3 ai channels at once, I observe a strange phenomenon in which the voltage along my (Dev3/ai3) channel follows the trend/is proportional to the voltage along my (Dev3/ai0) channel. Dev3/ai1 however is completely independent and functions as expected. Dev3/ai0 also displays the voltages I expect. However, Dev3/ai3 mimics the voltage detected along ai0.
However when I only add Dev3/ai3 to the task, I read the voltage that I expect to see.
Below is an image showing the expected behavior of Dev3/ai3
As seen above, readings are appropriately in the negative thousands.
However, as seen above, when reading multiple voltages, the current data follows the trend of the dev3/ai0.
My code is attached below
# Configure NI DAQmx settings
task = nidaqmx.Task()
# Channel ai3 is reading currentData
scale = nidaqmx.scale.Scale.create_lin_scale("currentScaler", 10000, pre_scaled_units = UnitsPreScaled.VOLTS)
task.ai_channels.add_ai_voltage_chan("Dev3/ai3", terminal_config=TerminalConfiguration.RSE, custom_scale_name="currentScaler", units = BridgeUnits(10065))
# Channel ai1 is reading the psu voltage
scale = nidaqmx.scale.Scale.create_lin_scale("psuVoltageScaler", 10, pre_scaled_units = UnitsPreScaled.VOLTS)
task.ai_channels.add_ai_voltage_chan("Dev3/ai1", custom_scale_name="psuVoltageScaler", units = BridgeUnits(10065))
# Channel ai0 is reading the saturation sensor voltage
task.ai_channels.add_ai_voltage_chan("Dev3/ai0")
task.timing.cfg_samp_clk_timing(rate=samplesPerSecond, sample_mode=AcquisitionType.CONTINUOUS, samps_per_chan=10000)
task.start()
timer = 0.0
while True:
try:
sample = task.read(nidaqmx.constants.READ_ALL_AVAILABLE)
for i in sample[0]:
currentDataArr.append(i)
timer = timer + (1.0/samplesPerSecond)
timeArr.append(timer)
for i in sample[1]:
psuDataArr.append(i)
for i in sample[2]:
saturationDataArr.append(i)
