Acquire Bridge Measurements

This example shows how to acquire and plot data from an NI 9219 module in CompactDAQ chassis NI cDAQ-9179. The device ID is cDAQ1Mod7.

Create a DataAcquisition object and save it to the variable d.

d = daq("ni");

Add an analog input channel for Bridge measurement type using the device channel ID ai1.

ch = addinput(d,"cDAQ1Mod7","ai1","Bridge");

You might see this warning:

Warning: The Rate property was reduced to 2 due to the default ADCTimingMode of this device,
which is 'HighResolution'.
To increase rate, change ADCTimingMode on this channel to 'HighSpeed'.

To allow a higher acquisition rate, change the channel property ADCTimingMode to 'HighSpeed'.

ch.ADCTimingMode = "HighSpeed"

You might see this warning:

Warning: This property must be the same for all channels on this device.  All channels
associated with this device were updated.

Change the acquisition rate to 10 scans per second.

d.Rate = 10;

Set the channel property BridgeMode to 'Full', which uses all four resistors in the device to acquire the voltage values.

ch.BridgeMode = "Full"

ch = 

Data acquisition analog input channel 'ai1' on device 'cDAQ1Mod7':

             BridgeMode: Full
       ExcitationSource: Internal
      ExcitationVoltage: 2.5
NominalBridgeResistance: 'Unknown'
                  Range: -0.063 to +0.063 VoltsPerVolt
                   Name: empty
                     ID: 'ai1'
                 Device: [1x1 daq.ni.CompactDAQModule]
        MeasurementType: 'Bridge'
          ADCTimingMode: HighSpeed

Set the resistance of the bridge device to 350 ohms.

ch.NominalBridgeResistance = 350

ch = 

Data acquisition analog input channel 'ai1' on device 'cDAQ1Mod7':

             BridgeMode: Full
       ExcitationSource: Internal
      ExcitationVoltage: 2.5
NominalBridgeResistance: 350
                  Range: -0.063 to +0.063 VoltsPerVolt
                   Name: empty
                     ID: 'ai1'
                 Device: [1x1 daq.ni.CompactDAQModule]
        MeasurementType: 'Bridge'
          ADCTimingMode: HighSpeed

Save the acquired data to a variable and start the acquisition.

data = read(d,seconds(1),OutputFormat="Matrix")

Plot the acquired data.

plot(data)