Acquire Bridge Measurements

This example shows how to acquire and plot data from an NI USB-9219 device. The device ID is 'cDAQ1Mod7'.

Create a session object and save it to the variable s:

s = daq.createSession('ni');

Add an analog input channel with the 'Bridge' measurement type and save it to the variable ch:

ch = addAnalogInputChannel(s,'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 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.

s.Rate = 10
s = 

Data acquisition session using National Instruments hardware:
   Will run for 1 second (10 scans) at 10 scans/second.
   Number of channels: 1
      index Type  Device   Channel MeasurementType              Range             Name
      ----- ---- --------- ------- ---------------- ----------------------------- ----
      1     ai   cDAQ1Mod7 ai1     Bridge (Unknown) -0.025 to +0.025 VoltsPerVolt

Set 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 = startForeground(s);

Plot the acquired data:

plot(data)

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