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Keysight 34450A Digital Multimeter: Specs and Checks

Quick answer: The Keysight 34450A is a 5½-digit, dual-display digital multimeter with AC true RMS voltage and current. Its user’s guide states a 1000 V DC and 750 V AC protection limit between the HI and LO inputs, and it lists the AC voltage input impedance as 1 MΩ. The guide also says the meter is for branch-outlet measurements up to 300 VAC, and that it must not be used with HI and LO connected to mains in permanently installed devices such as a main panel.

Quick answer

• Type: 5½-digit digital multimeter with a dual display mode.
• Stated input limit: 1000 VDC or 750 VAC between HI and LO. Also 1000 Vpk maximum.
• Stated category: IEC Measurement Category II, for devices plugged into a branch outlet, up to 300 VAC mains.
• Stated AC voltage input impedance: 1 MΩ ±2% in parallel with less than 100 pF on all AC ranges.
• Check before buying: the category for your circuit, the 10 A current input fuse, and whether you need the dual display for your work.

What the 34450A measures

The Keysight user’s guide, Manual Part 34450-90000 Edition 6 from July 2017, lists the measurement functions and ranges. DC voltage runs from 100 mV to 1000 V. AC voltage runs from 100 mV to 750 V and uses an AC-coupled true RMS method, which measures the AC component of the input. DC current has ranges up to 10 A, and AC current has ranges up to 10 A. The guide lists 100 mA as the top of the low-current input, with a separate 10 A terminal for higher current.

The guide also covers resistance, capacitance, diode tests, continuity, frequency, and temperature measurements. The front panel has a single display mode and a dual display mode. In the dual display mode the meter shows two measurements at once, and the guide lists which pairs can be shown together.

Input limits and impedance

The user’s guide states that the protection limit from HI to LO is 1000 VDC or 750 VAC, which it notes is also the maximum voltage measurement. It can also be expressed as 1000 Vpk maximum. The limit for the HI terminal relative to ground is a maximum of 1000 Vpk, and the guide says the sum of the float voltage and the measured voltage must not exceed 1000 Vpk.

On the AC voltage ranges the guide gives an input impedance of 1 MΩ ±2%, in parallel with less than 100 pF, on all ranges. For DC voltage the guide lists input impedance greater than 10 GΩ on the 0.1 V and 1 V ranges only, and about 10 MΩ on all ranges, as a typical figure. Input impedance affects how a meter loads a high-impedance circuit, so it matters if you measure sensitive signals.

Current inputs and fuses

The guide describes three current inputs. The mA input covers AC and DC current up to 100 mA, with a 0.4 A, 500 V fuse on the rear panel. The 10 A input covers AC and DC current from 1 A to 10 A, with an internal 11 A, 1000 V fuse. The guide notes that the 10 A terminal is protected by an internal fuse, and it says that only service-trained personnel should replace that fuse with one of the specified type and rating. Do not swap in a different fuse.

The quick start guide, Manual Part 34450-90007 Edition 4 from May 2025, covers the front-panel setup, including the resolution setting. Use it for the first steps, and use the user’s guide for the full specification.

Safety category: what the guide allows

The user’s guide describes the meter as designed to provide overvoltage protection for line-voltage mains connections that meet two conditions. The HI and LO inputs must be connected to mains under IEC Measurement Category II conditions, and the mains must be limited to a maximum of 300 VAC.

The guide defines Category II as electrical devices connected to mains at an outlet on a branch circuit, such as most small appliances, test equipment, and other devices that plug into a branch outlet. It says the 34450A may be used to measure in such devices or on the branch outlet itself, up to 300 VAC. It then says the 34450A may not be used with its HI and LO inputs connected to mains in permanently installed electrical devices, such as the main circuit-breaker panel, sub-panel disconnect boxes, or permanently wired motors. The guide says those circuits can have overvoltages above the meter’s protection limits.

The EDU34450A guide, Edition 1 from February 2021, repeats the same warning in its safety text. Our read: for a home outlet check, a light fixture, or a small appliance, the 34450A is within its stated category. For a service panel, a sub-panel, or a permanently wired circuit, it is not, and that work is for a licensed electrician to do.

Speed and resolution

The quick start guide lists the resolution settings. At the slow setting the meter reads at 5½ digits. The medium and fast settings read at 4½ digits, per the same guide. The user’s guide gives the AC speed settings as slow at 2 Hz, medium at 20 Hz, and fast at 200 Hz, and it says the default is autoranging at the slow setting. Pick the setting for the job. A slow reading gives more digits but updates less often, so it suits a steady bench measurement better than a fast-changing signal.

True RMS and crest factor

The guide says the 34450A’s AC measurement is AC-coupled true RMS, which measures the AC component of the input. It states a crest factor of up to 3:1 at full scale. The guide also has a section on high-frequency signal content, which explains that a true RMS meter’s accuracy depends on the waveform and bandwidth. If your signal is a non-sine waveform, read that section before you rely on the AC figure.

For a plain explanation of true RMS and when it matters, read our guide to true RMS multimeters. For the meaning of the markings on the front panel, see our guide to reading multimeter symbols.

Who the 34450A suits

From its guides, the 34450A suits bench and lab work where you need a 5½-digit reading, a dual display, and a current input up to 10 A. It is a good match for measurements on electronics, low-voltage DC systems, and circuits that the guide allows. It is not a clamp meter, and it does not measure current without opening a circuit. A clamp meter is the better tool for a live current check on a wire you cannot disconnect.

How we chose

This is a model explainer, not a ranking. We read three Keysight-family documents: the user’s guide Edition 6, the quick start Edition 4, and the EDU34450A user’s guide Edition 1. The EDU34450A is an education-branded version of the same meter, so we flag it as a variant copy and do not treat it as the main source. We did not use distributor listings, retailer pages, or review sites, and we did not include any claim we could not match to one of these documents.

What we could not verify

• The full DC voltage and DC current accuracy tables. The guides we read give ranges, impedance, and input limits, and we did not use a distributor’s accuracy figure in place of the manufacturer’s table.
• The official Keysight datasheet. We could not open a readable copy of it, so the specifications here come from the guides only.
• The exact CAT label printed on your unit. Confirm it on the front panel and the guide for your model.
• Typical performance in your own setup. The guides give specifications and conditions, not measurements from your bench.

FAQ

Is the Keysight 34450A true RMS?

Yes, for AC voltage and AC current. The user’s guide describes an AC-coupled true RMS method and a crest factor of up to 3:1 at full scale.

What is the maximum voltage it can measure?

The user’s guide states 1000 VDC and 750 VAC between HI and LO, which it also expresses as 1000 Vpk maximum.

Can I use it on the main panel?

No. The guide says the 34450A may not be used with HI and LO connected to mains in permanently installed devices such as a main circuit-breaker panel or sub-panel. Panel work belongs to a licensed electrician.

What fuse protects the 10 A input?

The guide describes an internal 11 A, 1000 V fuse for the 10 A terminal. It says only service-trained personnel should replace it, with a fuse of the specified type and rating.

What is the AC input impedance?

The guide gives 1 MΩ ±2% in parallel with less than 100 pF on all AC voltage ranges.

Does it have a dual display?

Yes. The user’s guide describes a dual display mode that shows two measurements at once, and it lists which pairs can be shown together.

Bottom line

The Keysight 34450A is a 5½-digit dual-display multimeter with AC true RMS and a stated 1000 VDC and 750 VAC input limit. Its guides place it in IEC Measurement Category II for branch-outlet use up to 300 VAC, and they rule out permanently installed mains circuits. Before you buy, check the category for your circuit, the 10 A fuse, and the impedance for your signal. If the work is a service panel or a permanently wired circuit, use a different tool and a licensed electrician.

Sources

• Keysight Technologies, Keysight 34450A 5½ Digit Multimeter User’s Guide, Manual Part 34450-90000, Edition 6, July 28, 2017 (copy hosted at https://ecse.rpi.edu/courses/static/ECSE-4770/Keysight_Equipment_User_Manuals/34450-90000.pdf). Opened 2026-10-27. Third-party copy of a manufacturer document.
• Keysight Technologies, Keysight 34450A 5½ Digit Multimeter Quick Start Guide, Manual Part 34450-90007, Edition 4, May 2025 (https://www.keysight.com/be/en/assets/9018-06057/user-manuals/9018-06057.pdf). Opened 2026-10-27. Manufacturer document hosted on keysight.com.
• Keysight Technologies, EDU34450A 5½ Digit Digital Multimeter User’s Guide, Edition 1, February 2021 (copy hosted at https://www.ee.torontomu.ca/guides/instrument-manuals/EDU34450A_Digital_Multimeter_User_Guide.pdf). Opened 2026-10-27. Education-branded variant of the 34450A; third-party copy, flagged in the text above.