How to set Excitation Voltage in a NI Compact DAQ bridge module

I can't set the ExcitationVoltage property without getting an error. I have an NI cDAQ-9178 chassis with a 9237 strain bridge module.

Script:

s = daq.createSession('ni');

%cDAQ1Mod3 is a NI 9237 strain bridge module in a cDAQ-9178 chassis
s.addAnalogInputChannel('cDAQ1Mod3',[0 1 2 3],'Bridge');

%handle to the channels in the object
ch = s.Channels

current_excitationvoltage = get(ch,'ExcitationVoltage')
%returns a 4x1 cell array of the excitation voltage values for the 4
%channels

%DAQmx is looking for a double...create it
new_exc = double(10.0);

%now put it in a 4x1 cell array
new_excitationvoltage = {new_exc new_exc new_exc new_exc}'

%now try to set it in the channels object
set(ch,'ExcitationVoltage',new_excitationvoltage);

Output:

ch = 

Number of channels: 4
   index Type  Device   Channel MeasurementType              Range             Name
   ----- ---- --------- ------- ---------------- ----------------------------- ----
   1     ai   cDAQ1Mod3 ai0     Bridge (Unknown) -0.025 to +0.025 VoltsPerVolt
   2     ai   cDAQ1Mod3 ai1     Bridge (Unknown) -0.025 to +0.025 VoltsPerVolt
   3     ai   cDAQ1Mod3 ai2     Bridge (Unknown) -0.025 to +0.025 VoltsPerVolt
   4     ai   cDAQ1Mod3 ai3     Bridge (Unknown) -0.025 to +0.025 VoltsPerVolt

current_excitationvoltage = 

      [2.5000]
      [2.5000]
      [2.5000]
      [2.5000]

new_excitationvoltage = 

      [10]
      [10]
      [10]
      [10]

Error using internal.SetGetRenderer/set (line 47)
ExcitationVoltage must be a positive, non-zero scalar double.

Error in cdaq_test_bridge (line 20)
set(ch,'ExcitationVoltage',new_excitationvoltage);

Answer 1

[Rick]

Just tried it...unfortunately, that didn't work. Same error. I had put it in a cell array just because that was how the values were returned when I queried the property. In any case, putting it in a normal vector seems to generate the same error.

Any more ideas? Thanks

Answer 2

[Marco]

I don't know if this helps, but I had a similar problem. Since I'm using 2 channels, I just configured one first, then added the second channel and the FIRST thing I changed was the excitation voltage to match the first one, and ... it worked !

See the code below:

devices = daq.getDevices;
DAQ = devices(1);
ID = get(DAQ,'ID')
s = daq.createSession('ni');
s.Rate = 25000;

Chan1 = s.addAnalogInputChannel(ID, 0, 'Bridge');
set(Chan1,'BridgeMode','Full');
set(Chan1,'NominalBridgeResistance',1000);
set(Chan1,'ExcitationVoltage',10.0);

Chan2 = s.addAnalogInputChannel(ID, 1, 'Bridge');
set(Chan2,'ExcitationVoltage',10.0);
set(Chan2,'BridgeMode','Full');
set(Chan2,'NominalBridgeResistance',1000);

Answer 3

[MoeIsKing]

Does anyone knwo how to set the channel to zero?

Or how do you "scale" the channel later, as you don't know what signal voltage is which force/weight/reference?