changing DAQmx channel gain

[pblase]

(Windows XP, LabWindows/CVI 10, PCIe-6361).

I set up a DAQmx data acquisition task in MAX, with the voltage range set for each channel, but the user wants the option to change the voltage range in the program. So I put in:

               //some stuff

               x = new max or min value

               bMax = 1 if setting Max, 0 if setting Min.

                //stop task
                status = DAQmxStopTask (Level1_Task_p->DAQTask_Handle);
                
                
                //update value
                status = DAQmxSetChanAttribute (Level1_Task_p->DAQTask_Handle,
                                                ChannelInfo[channel].ChannelName,
                                                (bMax) ? DAQmx_AI_Max : DAQmx_AI_Min,
                                                x,
                                                1);
                //confirm value
                status = DAQmxGetChanAttribute (Level1_Task_p->DAQTask_Handle,
                                                ChannelInfo[channel].ChannelName,
                                                (bMax) ? DAQmx_AI_Max : DAQmx_AI_Min,
                                                &x,
                                                1);
                //some other stuff

               ......

                //restart task
                status = DAQmxStartTask (Level1_Task_p->DAQTask_Handle);
                
It stops the task, sets the max or min value of the channel (you can only set one at at a time) to the value of "x", confirms the coerced value by reading it back, and restarts the task.

The problem is that it can only set the voltage range heigher, never lower. I have the max and min nominally set to +5 and -5 V. If I enter 10 for the value, it reads back as 10. If I then set it to 1, it reads back as 10.  Any ideas would be appreciated.

[MilanR]

Hi pblase,

You should be able to achieve this functionality by clearing the task and creating a new task with the new amplifier settings and starting that task. This would be a solution as long as the amplifier settings are not being changed very quickly, like in this case when the user decides to change the amplification setting manually.