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04 | Keysight | Compatibility and Differences: 34461A and 34401A Digital Multimeters - Application Note
Key measurement differences
– The 34461A and 34401A use different calibration procedures, with different default
passwords.
– Some specications vary between the 34461A and the 34401A. In general, the
34461A specications equal or exceed those of the 34401A. One exception: the
34401A’s 3-A range is slightly better than the 34461A. For best current measure-
ment results above 1 A, use the 34461A’s 10-A input terminal.
– The 34461A has additional current ranges: 100 µA, 1 mA, and 10 A. Therefore, the
MIN and MAX parameters produce different results. In addition, autorange on the
34461A may use different ranges than on the 34401A, and autoranging may take
longer.
– Burden voltage is generally lower on the 34461A than the 34401A.
– 34461A uses a digital AC measurement technique. This produces better linearity and
a sharper bandwidth roll off for AC measurements.
Key programming differences
– The 34461A does not support the older 3478A or Fluke 8840A programming lan-
guages.
– The INIT command on the 34401A is non-overlapped, except when bus trigger-
ing (*TRG) is selected. This means that CONF:VOLT:DC;:INIT;:CONF:CURR:DC;:INIT
makes two measurements. The INIT command on the 34461A is overlapped, and the
above sequence generates an error message.
– By default, the 34461A *IDN? query returns:
– Keysight Technologies,3446xA,<Serial Number>,ff.ff-pp.pp-mm.mm-gg.gg-bb-pp
– The 34461A parses and executes commands faster than the 34401A. The 34461A
also supports overlapped command processing between INIT and measurement
completion. Proper synchronization with *WAI and *OPC? minimizes the impact.
Existing systems that depend (intentionally or unintentionally) on 34401A command
execution speed for timing may experience subtle timing issues.
– The 34461A requires less settling time than the 34401A, yielding shorter default
trigger delays. Therefore, if you use default trigger delays, these delays may start a
measurement before your DUT has settled, which means that a signal that was fully
settled when measured on the 34401A will still be settling on the 34461A.
– The 34461A and the 34401A may generate different error messages. This is usually
not a problem, because existing programs normally do not generate SCPI errors.
– The 34461A can store up to 10,000 readings, which is more than the 512 that the
34401A allows. This is unlikely to affect existing programs.
– The 34461A denes bits in the questionable data and status byte registers that were
unused by the 34401A. Programs that properly mask unused bits will minimize is-
sues associated with querying these registers.
– Under certain conditions, the 34461A may return and display negative resistance
values. For details, see [Help] > Negative Resistance Values from the front panel.
– The 34461A always puts readings into memory. When the READ? query nishes, a
subsequent FETCh? returns those same readings. In a similar situation, the 34401A
shows memory as empty. Also, if the computer is not taking readings fast enough,
the 34401A slows down to avoid losing readings. The 34461A does not allow the
computer to pace its reading rate.
– To support testing a wider range of diodes, the compliance voltage has been in-
creased from 1.2 V to 5.05 V. The range for the 34461A is xed at 10 V, as opposed
to 1 V on the 34401A. The current source remains xed at 1 mA.
– The dBm reference on the 34461A is a volatile value. It was non-volatile on the
34401A.