Is an HP 34401A identical to an Agilent 34401A?

Yes. Aside from cosmetic changes such as logo badges and bumper colors, the electrical specifications, measurement functions, and programming commands are identical.

Can I use Keysight software with older HP-branded instruments?

Generally, yes. Since the underlying command sets (like SCPI) and physical interfaces (such as GPIB) did not change during the spin-offs, modern Keysight software suites are backward-compatible with legacy Agilent and HP models.

HP vs Agilent vs Keysight: One Instrument Line, Three Names

For engineers and technical buyers browsing the used test equipment market, seeing the exact same instrument model branded as Hewlett-Packard, Agilent, or Keysight can be confusing. This branding evolution is the result of two corporate spin-offs. In 1999, Hewlett-Packard spun off its test and measurement division to form Agilent Technologies. Later, in 2014, Agilent spun off its electronic measurement group to establish Keysight Technologies.

Because of these transitions, iconic instruments frequently exist under multiple brand names with identical specifications. Understanding this lineage helps when searching for manuals, sourcing replacement parts, and verifying compatibility between legacy hardware and modern setups.

HP to Agilent Spin-off: 1999
Agilent to Keysight Spin-off: 2014
Model Number Continuity: Maintained across brand transitions

The Evolution of the Brand Names

The transition from HP to Agilent and eventually Keysight represents continuity rather than a series of acquisitions. When Agilent was created in 1999, it inherited the entirety of HP's electronic measurement heritage, including factory facilities, engineering teams, and existing designs. The same transition occurred in 2014 when Keysight became an independent company dedicated entirely to electronic measurement.

Consequently, an instrument manufactured during a transition year may carry physical branding from one company but include internal circuit boards or boot screens bearing the logo of another. Despite these aesthetic differences, the electrical performance and structural design of the units remained consistent.

Continuity in Action: Case Studies

The naming transition is best understood by looking at classic instrument models that spanned these eras:

The 34401A Digital Multimeter: This 6½ digit multimeter was originally designed and sold under the Hewlett-Packard name. It continued production under Agilent and was supported into the Keysight era, before the Keysight 34461A was introduced as its direct replacement.
Spectrum and Signal Analyzers: The 8563E microwave spectrum analyzer (9 kHz to 26.5 GHz) and the E4407B spectrum analyzer were sold under both HP and Agilent badges. Later analyzers, such as the N9020A signal analyzer, debuted under Agilent and transitioned to Keysight branding.
Network Analyzers: Instruments like the 8753ES vector network analyzer (offering component characterization from 30 kHz up to 6 GHz) can be found with either Agilent or Keysight faceplates, depending on their exact year of manufacture.

How to Find Manuals and Support

Because Keysight is the current custodian of this product line, almost all legacy support documentation has been consolidated under the Keysight name.

When searching for manuals or software drivers for older HP or Agilent hardware, use the original model number. For example, searching for "Keysight 34401A" will lead to the official documentation portal, even though the downloaded PDF manual may still feature the original HP or Agilent logo on its title page. Calibration procedures and basic electrical specifications remain identical across the different branded versions of a given model number.