The badge on an HP, Agilent or Keysight instrument mostly tells you when it was built. One test and measurement business made all of it, and the name on the front panel changed when the company did. Judge a used unit on its condition, hours and calibration history, and treat the badge as a rough date stamp.
From HP to Agilent to Keysight
- 1939. Bill Hewlett and Dave Packard start Hewlett-Packard in a one-car garage in Palo Alto. Their first hit is the 200A audio oscillator, and Walt Disney Studios buys eight of them for Fantasia.
- 1960s to 1975. HP develops the HP Interface Bus to connect instruments to controllers. The IEEE standardizes it as IEEE 488 in 1975, and that's the GPIB connector on the back of most of the gear here.
- 1999. HP spins off everything outside computers, storage and imaging as Agilent Technologies, test and measurement included. Agilent's stock offering was the biggest in Silicon Valley's history at the time.
- September 19, 2013. Agilent announces it will split into two companies.
- November 1, 2014. The split completes. The electronic measurement business becomes Keysight Technologies, based in Santa Rosa, California, and Agilent carries on making laboratory instruments for pharmaceutical, diagnostic and research work.
The product lines went straight through each change. Keysight's own data sheet for the 34461A says it was designed by the same team that created the 34401A, a meter that started out with an HP badge.
Why one model wears different badges
Production didn't stop for a name change. A model that was still in the catalog in 1999 or 2014 kept being built, and the new badge went on the front. The 34401A shows it best. It's an HP-era design, from the same period as HP's 3458A, and Keysight only discontinued it on December 1, 2016. So you'll find HP, Agilent and Keysight 34401As for sale, and the Keysight ones are the last of the run.
For a buyer, that means two things. An HP badge points to an older unit, with more years on its capacitors, switches and display. A badge that changed partway through a model's life is a date, so compare units on condition, firmware revision, hours and cal history. Don't pay extra for a logo you happen to like unless the rest of the unit earns it.
Model by model
- HP 3457A. One of the older HP designs in our catalog. Keysight lists it as obsolete with free self-support through its website, and its service centers still offer repair and calibration. Keysight points 3457A owners to the 34401A, 34410A, 34411A and 3458A as alternatives.
- 34401A. A 6½-digit meter with 10 measurement functions and up to 1,000 readings a second. After the December 2016 discontinuation, Keysight committed to its standard five years of support, and it names the 34461A and 34465A as replacements. On old units, the front and rear input selector switch is a known weak spot, because dirty contacts stop making a low-resistance connection.
- E3631A. An 80 W triple-output supply, 0 to 6 V at 5 A plus 0 to +25 V and 0 to -25 V at 1 A, with GPIB and RS-232. Keysight lists it as obsolete and names the E36311A and E36312A as the next generation. Its page also warns that counterfeits of this or closely related products have been found, so buy from a seller who shows the real serial label and the supply working.
- 8656B. A synthesized signal generator covering 0.1 to 990 MHz. Keysight lists it as obsolete, still offers support, service notes and calibration, and suggests the N5171B EXG as the modern replacement.
- 8562A. A portable spectrum analyzer that reaches 22 GHz. Keysight lists it as obsolete with self-support through the website, and offers repair and calibration through its service centers. It suggests the N9020B MXA or N9030B PXA as replacements.
- 34461A. The 6½-digit Truevolt meter, still a current Keysight model, with LAN and USB as standard and GPIB as an option. Keysight calls it a drop-in, SCPI-compatible replacement for the 34401A. If you find one with an Agilent badge, it was built before the November 2014 split.
Manuals, support and calibration
Keysight keeps product pages for obsolete HP and Agilent models, with the data sheet, service notes and links into its support portal. Search Keysight's site by model number, even for an HP-badged unit, because that's where the page lives now. For many older models the page says support is self-service through the website, while Keysight's service centers can still repair and calibrate a lot of them. Independent cal labs work on these too. Our calibration guide explains what a certificate should show, and why a sticker alone doesn't prove much.
If you plan to drive an instrument from a computer, its age matters more than its badge. SCPI, the common command language most later gear speaks over GPIB, became an industry standard in 1990, and IEEE 488.2 standardized the common commands in 1987. Instruments designed before then use their own HP-IB command sets, so get the programming manual for the exact model. The 34461A is the easy case, since Keysight built it to take 34401A commands.
What to check, whatever the badge
- Serial label. Ask for a photo of the rear label. The model number on it should match the front panel and the title.
- Power-on. Ask for a photo of the display after power-on and self-test. It should show a normal reading with no error message.
- Calibration. Ask for the certificate if the title says "calibrated". A dated cert from a named lab with measured data counts, and a sticker on its own doesn't.
- Interfaces. Look at the GPIB and RS-232 connectors in the photos. They should be straight, clean and complete.
- Inputs. On a meter, ask whether the current-input fuses are intact. Blown fuses or scorched jacks point to a meter that's been overloaded.
- Mains setting. Ask what line voltage the unit is set for, and check it on arrival before you plug in. A unit shipped from a 230 V country may need its setting changed for 120 V.
- Packing. Ask how it will be packed. Heavy bench gear should travel double boxed, and knobs, BNC connectors and front-panel glass are what usually break.
Our eBay red flags guide covers the listing tells that apply to everything. See every model on the HP / Agilent / Keysight page, compare multimeters across brands, or browse the full catalog.
