HP34401A Read Meas

Reads the measurement selected by the HP34401A Config Measurement or HP34401A Config Math VI. This VI waits for data to become available until the Timeout value is reached. If the time expires prior to reading the data, a timeout error is returned. Refer to the HP34401A Config Measurement and HP34401A Config Math VIs for more information. Details

Timeout is for reading back the data from the multimeter. Depending on the communications interface and the mode of operation, different nodes in the VI will be the slow step in VI operation and control Timeout.

  • Buffer Set to Internal—If Buffer is set to Internal, Timeout is the time needed to read the samples from the multimeter.
  • Buffer Set to Output—If Buffer is set to Output, Timeout also includes the time required for the multimeter to measure the data. If the multimeter is set to external triggering, the time between external triggers must also be considered when setting this value.
  • GPIB Interface Operating in the Retrieve ALL and BLOCK Modes—With internal buffering, <512 points, the meter only asserts RQS after all data is collected. Therefore, the VISA RQS node generally requires more time than the VISA Read node and is primarily responsible of controlling the timeout.

    Without internal buffering, the meter asserts RQS after the first trigger point is received. Therefore, the VISA Read node generally requires more time than the VISA RQS node and is primarily responsible of controlling the timeout.
  • Serial (Not GPIB) Interface Operating in the Retrieve ALL and BLOCK Modes—The VISA Read node is primarily responsible for controlling Timeout. Since the meter only begins transmitting data after collection is complete, when using the internal buffering, <512 points, the VISA Read timeout value must provide enough time for data collection and data transfer.
VISA session is a unique reference to an instrument I/O session. It identifies which device to communicate with and all configuration information to perform the I/O. A VISA session is a unique logical identifier used by VISA to communicate with a resource. The VISA session is maintained by the VISA resource name control and is not seen by the user.
Software Trigger determines if software triggers are sent to the multimeter. The number of software triggers is equal to the value set in the HP34401A Config Trigger VI. For software triggering, this control must be TRUE. For internal or external triggering, this control must FALSE (default). If this control is TRUE, the VI ignores the Buffer setting.

If internal triggering is selected, the fastest sampling rate can be achieved by turning off the autozero setting, selecting a fast filter, and turning off autoranging.

Data Storage stores the data to be sent to either the internal or external buffer. If TRUE (default), the VI stores data in the on mode. If FALSE, the VI does not retain data in the off mode. Use the off mode only with the average min/max operation when you do not need to retrieve data. You cannot configure the meter for external buffering in the off mode.
Buffer specifies whether the VI sends output data directly to the output buffer, or stores the data temporarily in an internal buffer before sending it to the output buffer. If TRUE, the VI sends output data to the output buffer. If FALSE (default), the VI sends output data to the internal buffer. The multimeter can acquire data faster when the data is saved to the internal buffer first. However, the number of samples is limited because the internal buffer can store only 512 measurements. For sample counts larger than 512, data must be transferred directly to the output buffer. If Software Trigger is TRUE, the VI ignores the Buffer setting.

When using the external buffer, the data must be read from the meter fast enough to prevent the buffer from filling. If the buffer completely fills, data collection stops until the buffer is read. The VI does not return an error showing this data loss.

error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurs before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node.
status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE.
code is the error or warning code. The default is 0. If status is TRUE, code is a non-zero error code. If status is FALSE, code is 0 or a warning code.
source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
Start Meas indicates when to start taking measurements. You can select from three primary modes of data collection. Start Meas varies depending on which mode is in use. Use TRUE (default) when the Initiate and Collect All mode or the Initiate Only mode is active. When operating in the Block Transfer mode, use TRUE for the first call to this VI. Use FALSE for all subsequent calls to the VI until data transfer is complete.
# Points sets the number of points to be retrieved per read cycle when using the Read Block mode. Normally, the multimeter takes one reading each time it receives a trigger from the selected trigger source. However, you can instruct the multimeter to take multiple readings for each trigger received. The valid range is 1 to 50,000 samples per trigger. The default value is one sample per trigger.

Note  If a value is outside the given range, it is changed to the nearest acceptable value. If data is sent to the internal buffer, the maximum number of samples to be read is 512.
dup VISA session is a copy of VISA session. Use dup VISA session programmatically to pass VISA Session to any calling VIs.
End of Data responds to the three primary modes of data collection. If TRUE, the Initiate and Collect All mode or the Initiate Only mode is active. This VI only returns TRUE in the Block Transfer mode after it receives a termination character from the meter. The termination character is sent after collection and transmission of all data is complete. If FALSE, the meter will continue to transmit data.
Measurements displays the output of the selected function. This includes all mathematical operations except MIN/MAX. This array records all measurements taken when multiple triggers or samples are selected.
error out contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces. Right-click the error out indicator on the front panel and select Explain Error from the shortcut menu for more information about the error.
status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred.
code is the error or warning code. If status is TRUE, code is a non-zero error code. If status is FALSE, code is 0 or a warning code.
source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

HP34401A Read Meas Details

You can choose the operating mode of the HP34401A Read Meas VI from the following modes of operation: