What is the difference between the FULL and COMPACT Buffer Data Groups for the Model 2001 and 2002 DMMs?
The Data Group selection determines what information is stored in the Trace Buffer (Data Store). When FULL is selected, the data stored in the buffer includes the reading, units, channel number (if applicable), reading number, timestamp, and status. The maximum number of data points that can be stored in the buffer using the FULL Data Group ranges from 250 with no memory option up to 6,000 with the MEM 2 memory option. Readings up to the full resolution of the instrument, 7.5 digits for the 2001 and 8.5 digits for the 2002, can be stored. The FULL data group also allows the function, range, or channel to change while storing, as when scanning or using autorange.
When COMPACT is selected, the data stored in the buffer includes the reading, units, reading number, and status. The maximum number of data points that can be stored in the buffer using the COMPACT Data Group ranges from 850 with no memory option up to 30,000 with the MEM 2 memory option.
However, there are other differences between the COMPACT and FULL data groups than just the amount of data stored. Readings stored using COMPACT are only accurate and displayed to 5.5 digits. Also, the function, range, or channel should not be changed while storing with COMPACT selected. Note that these DMMs actually allow COMPACT and autorange to be enabled simultaneously without generating an error, but invalid readings will result if the range changes after the first reading is stored.
The COMPACT Data Group should only be used when storage capacity is of greatest importance and single function, fixed range, limited resolution measurements can be made. If more than 5.5 digits of resolution are required, or if you want to perform scans controlled by the DMM, or if autoranging is required, then you must use the FULL Data Group. Also, you should not use COMPACT if your only goal is to eliminate the timestamp from the data you read back from the DMM. You should use the "FORMAT:ELEMENTS <item list>" command and leave the timestamp out of the item list.
To select FULL or COMPACT from the front panel, press and release the CONFIG key and then press the STORE key. Select DATA-GROUP at the CONFIG DATA STORE menu and press ENTER. Select FULL or COMPACT at the BUFFER DATA GROUPING menu and press ENTER. Exit out of the menus. To select FULL or COMPACT under remote control, send "TRACE:EGROUP FULL or COMPACT" to the DMM.