HP WaterSkis E1312A, WaterSkis E1412A manual Setting the Resolution, Initfetch?

Setting the Resolution

Store the Readings in Multimeter RAM Instead of Sending them Directly to the Computer

INIT;:FETCH?

The aperture time or NPLC is set as a result of specifying the <resolution> parameter in the MEASure or CONFigure command, or by directly setting it with the [SENSe:]FREQuency:APERture or [SENSe:]PERiod:APERture command or [SENSe:]function:NPLC commands.

There is a major difference between INIT;:FETCh? and READ? after a CONFigure command.

When the INITiate command is sent to the HP E1312A or HP E1412A, the multimeter will store up to 512 readings in Multimeter RAM. For example:

CONF:VOLT:DC

SAMP:COUN 200

INIT	! Stores 200 readings in RAM
FETC?	! Transfers readings to output buffer

The HP E1312A or HP E1412A then takes the readings as soon as its trigger conditions have been satisfied and stores them in internal memory (RAM). For example, if the trigger source is IMMediate, the readings are started once INITiate is executed. If the trigger source is EXT, then the readings are started when an external trigger is received.

The FETCh? command causes the readings that have been stored in the multimeter RAM to be placed in the multimeter’s output buffer so they can be retrieved and sent over the HP-IB bus (or other I/O interface such as VXLink). No readings are output until all readings have been taken and stored in internal memory (RAM). This results in a burst-then-transfer mode of operation. The multimeter can store a maximum of 512 readings in its internal memory.

READ? The READ? command does not store readings in internal memory (RAM) like the INITiate command does. For example:

CONF:VOLT:DC

SAMP:COUN 200

READ? ! Takes 200 readings and puts them in the output buffer

The READ? command causes the HP E1312A and HP E1412A Multimeter to start taking readings as soon as the trigger requirements have been met. For example, if the trigger source is IMMediate, the readings are started immediately. If the trigger source is EXT, then the readings are started when an external trigger is received. The multimeter immediately places those readings in the multimeter’s output buffer so they can be retrieved via the HP-IB bus (or other I/O interface such as VXLink) by the controller. If the controller cannot take the readings from the output buffer fast enough, the multimeter will suspend taking measurements until there is room to place the readings in the output buffer. You can have a variable reading rate if your controller is busy doing other tasks instead of emptying the output buffer to make room for more readings.

198 Measurement Speed and Accuracy Trade-offs Appendix C