.. _userTutorialsRecordIVCurve:

Record an I/V Curve
===================

This tutorial describes a typical procedure for measuring the current/voltage relationship of a neuron using the :ref:`Task Runner <userModulesTaskRunner>`. This tutorial is run from the example configuration, using a :ref:`simulated patch clamp amplifier <userDevicesMockClamp>` and neuron.

#. Start ACQ4, then from the module list in the Manager window, select "Task Runner" and click **Load Module**.
#. In the Task Runner, check the box next to "Clamp1" under **Devices**. The task interface for the simulated clamp device will appear. Notice the tas at the bottom of the window; the DAQ configuration including the sample rate can be accessed here. 
#. At the top-left of the newly created dock, click on **vc**, then select **ic** from the list.
#. In the task settings dock, just beneath the device list, click **Test**. A noisy recording should appear; you have just recorded 200 ms of current-clamp data from a Hodgkin-Huxley neuron.
#. In the same dock, change **Duration** to 400 ms.
#. Now we will create a square-pulse waveform to stimulate the cell:
    #. In the :ref:`function generator <userInterfacesFunctionGenerator>` for the clamp device, click **Add Stimulus**, then **Pulse**.
    #. Change the pulse **amplitude** to 50 pA, then click **Update**. A square-pulse waveform appears, colored red. 
    #. Check **Auto** adjacent to the **Update** button; this will make the stimulus waveform automatically update as we adjust it.
    #. Change **start** to 50 ms and **length** to 200 ms; verify that the square-pulse waveform has changed accordingly.
    #. Click **Test** again, just for fun.
#. Next, we will create a sequence of pulses at different amplitudes:
    #. Expand the **amplitude** parameter by clicking the arrow (or +) immediately to its left.
    #. Change the **sequence** parameter to **range**.
    #. Make the start value -100 pA, and the stop value 100 pA.
    #. Check that a sequence of pulses is now visible in the waveform plot. Sequence waveforms are plotted in grey. 
    #. Check that an item called "Clamp1 command.Pulse_amplitude" has appeared in the **Sequence Parameters** list. 
    #. Just below the **Sequence Parameters** list, click **Test**.
    #. The entire sequence executes, plotting each result one at a time. Note this will run a bit slow because it is simulating the neuron; a real experiment would be much faster.