Bought a used HP 34401A 6½-digit multimeter on Xianyu for 1800 RMB, a classic multimeter.
Seller claims it’s original and unmodified, calibrated before shipping (calibration equipment: Fluke 5500A).
Unboxing and review of the Zhongchuang ET4410 benchtop LCR meter: https://blog.zeruns.com/archives/763.html
Unboxing and review of the Rigol DHO914S oscilloscope: https://blog.zeruns.com/archives/764.html
Open-source project sharing: https://blog.zeruns.com/tag/open-source/
Electronics/Microcontroller technical discussion group: 2169025065 (Group files include various resources, e-books, software, etc.)
34401A Specifications and Introduction
- 6½-digit resolution
- 10 measurement functions: DC/AC voltage, DC/AC current, 2-wire and 4-wire resistance, diode, continuity, frequency, period
- Basic accuracy: 0.0035% DC, 0.06% AC
- Maximum input: 1000 V voltage, 3 A current
- Up to 1000 readings per second
- 512-reading memory
The HP 34401A offers high-precision measurements with a 6.5-digit resolution, supporting DC/AC voltage, DC/AC current, 2-wire and 4-wire resistance, diode, continuity, frequency, and period measurements. Its basic accuracy is 0.0035% for DC and 0.06% for AC, with maximum input ratings of 1000 V and 3 A. Additional features include math operations, continuity and diode testing, and the ability to store up to 512 readings.
Regarding the relationship between HP, Agilent, and Keysight: The 34401A was originally introduced by Hewlett-Packard (HP). As the company evolved and restructured, the product line transitioned through Agilent Technologies and eventually to Keysight Technologies. Agilent was originally a division of HP before spinning off in 1999. Then in 2014, Agilent split into two companies: its electronic measurement division became Keysight Technologies, while the life sciences, chemical analysis, and diagnostics division retained the Agilent name.
- Keysight 34461A 6½-digit multimeter purchase link: https://u.jd.com/H8s63b7
- Rigol DM858E 5½-digit multimeter purchase link: https://u.jd.com/HQs8GnV
- UNI-T UT61E+ 4½-digit multimeter purchase link: https://u.jd.com/HzsGP7C
Document Downloads
The following links include these files: Agilent 34401A English User Manual (with schematics), Agilent 34401A Chinese User Manual, HP 34401A User’s Guide, and HP 34401A User’s Guide (Chinese version, machine-translated).
123Pan download link (no speed limit): https://url.zeruns.com/3AJ1e
Baidu Pan download link: https://pan.baidu.com/s/1FtMGDHwBjwG5te-UvXcjcA?pwd=gnm9 Password: gnm9
Device Photos
Front view
Side view
Back view
Testing
Test equipment used: Redeng RD6012P adjustable DC power supply, ET4410 LCR meter, UNI-T UT61E+ 4½-digit multimeter.
Since I don’t have a source meter or calibration instrument, I can’t verify the absolute accuracy of this unit. I can only compare it with the UT61E+ (a newly purchased meter) or trust the seller’s claim of prior calibration.
If your device hasn’t been calibrated, you can pay someone on Xianyu to calibrate it, or use a professional metrology service.
Press and hold the Shift key while powering on to enter self-test mode.
Self-test passed
This multimeter has likely been used for many years; the fluorescent display is dim but still functional.
DC Voltage Measurements
Ranges: 100mV, 1V, 10V, 100V, 1000V (750Vac)
TL431 reference at ~2.5V: 34401A reads 2.50078V, UT61E+ reads 2.501V.
RD6012P set to 1V output: 34401A reads 0.999822V, UT61E+ reads 0.9996V.
RD6012P set to 10V output: 34401A reads 10.00119V, UT61E+ reads 10.001V.
RD6012P set to 24V output: 34401A reads 24.0001V, UT61E+ reads 24.00V.
RD6012P set to 0.1V output: 34401A reads 99.4128mV, UT61E+ reads 99.56mV.
DC Current Measurements
Ranges: 10mA (DC only), 100mA (DC only), 1A, 3A
Test method: Connect RD6012P output in series with both multimeters.
RD6012P set to 0.1A constant current: 34401A reads 100.9515mA, UT61E+ reads 100.91mA.
RD6012P set to 1A constant current: 34401A reads 1.000790A, UT61E+ reads 1.001A.
RD6012P set to 2.5A constant current: 34401A reads 2.49837A, UT61E+ reads 2.500A.
AC Voltage Measurements
Ranges: 100mV, 1V, 10V, 100V, 750V
DHO914S oscilloscope outputs a 1kHz, 3Vpp square wave. Oscilloscope measures RMS voltage as 1.4630V, 34401A reads 1.4629V (forgot to set digit count), UT61E+ reads 1.4828V.
DHO914S outputs a 500kHz, 5Vpp sine wave. Oscilloscope measures RMS voltage as 1.7438V, 34401A reads 1.73428V, UT61E+ reads 1.6377V.
Frequency Counter
Frequency range: 3Hz to 300kHz (0.33sec to 3.3μsec)
Input signal range: 10mVac to 750Vac
DHO914S outputs a 1kHz square wave. Oscilloscope measures 1kHz, 34401A reads 1.00004kHz, UT61E+ reads 0.9998kHz.
DHO914S outputs a 500kHz sine wave. Oscilloscope measures 500.19kHz, 34401A reads 500.0172kHz, UT61E+ reads 0.4999MHz.
Diode Test
Test current source: 1mA
Maximum resolution: 100μV (fixed range at 1Vdc)
Beeper threshold: 0.3V ≤ measured V < 0.8V (not adjustable)
Testing 1N5822 diode: 34401A reads 0.21964V, UT61E+ reads 0.2075V.
Resistance Measurements
Ranges: 100Ω, 1kΩ, 10kΩ, 100kΩ, 1MΩ, 10MΩ, 100MΩ
Maximum resolution: 100μΩ (on 100Ω range)
The following resistance measurements with the 34401A use 4-wire (Kelvin) method.
Testing a 0805 10Ω resistor with 0.1% tolerance: ET4410 LCR meter reads 10.006Ω, 34401A reads 10.0100Ω, UT61E+ reads 10.07Ω.
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