Fetch Operation - Edit IVI Dmm Step Dialog Box

Fetch Operation

The Fetch operation returns the measured value from a measurement the Initiate operation started. If the Trigger Count is greater than 1 and the Multi Point extension is enabled, the Fetch operation returns an array of values. Otherwise, the Fetch operation returns a single value.

Typically, this operation is only called in a sequence of calls to other low-level driver operations, such as the Initiate operation. Before issuing a Fetch operation, use the Initiate operation in a separate step to initiate a measurement.

Note If you perform other operations on the instrument after the call to an Initiate operation but before issuing a Fetch operation, the Fetch operation may not return valid data.

The Fetch operation contains the following options:

  • Data Type —Specifies whether the step expects a single value or array of values. The step coerces the data type of the Step.Result.Reading property to NI_IviSinglePoint or NI_IviWave , respectively.
  • Measurement Destination —A variable or property, as the following table describes, to which the step assigns the measurement value.
    Value Type Data Type of the Variable or Property
    Single values Number or NI_IviSinglePoint
    Array of values Array of Number or NI_IviWave
    The default configuration for the step specifies Step.Result.Reading as the destination. When you edit the step, the step automatically coerces the data type of the Step.Result.Reading property to NI_IviSinglePoint or NI_IviWave , based on the value of the Data Type control. If you do not specify Step.Result.Reading as the destination, TestStand copies the measurement value to the Step.Result.Reading.Data property at run time unless the Copy Data to Execution Results option is disabled.
  • Timeout (ms) —The timeout, in milliseconds, for the operation. The Timeout setting applies to the length of time between initializing a call to Read and completing the data acquisition, not the time the DMM requires for computations or to transfer data across the instrumentation bus. To set an infinite timeout, set Timeout to -1 .
  • Set Status on Timeout —The status for the step result when a timeout condition occurs. When you leave this control blank, the step ignores timeout conditions.
  • Set Status if Over-Range —The status for the step result when a timeout condition occurs. When you leave this control blank, the step does not check for an over-range condition.
  • Copy Data To Execution Results —When you enable this option, TestStand copies the measurement value stored in the property Step.Result.Reading.Data to the step result. When you enable this control, TestStand cannot include the measurement in a report or log the measurement to a database. This setting is always enabled for single-point measurements.