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Keithley DMM6500 6.5-Digit Multimeter: Specs and Checks

Quick answer: The Keithley DMM6500 is a 6½-digit bench and system multimeter from Keithley Instruments, now part of Tektronix. Its reference manual states it measures DC voltage from 100 nV to 1000 V and AC true RMS voltage from 0.1 V to 750 V. The manual also says its front and rear terminals are rated for Measurement Category II up to 300 V, and that it must not be connected to CAT III or CAT IV circuits.

Quick answer

• Type: 6½-digit bench and system multimeter with scanning options.
• Stated DC voltage range: 100 nV to 1000 V. Stated AC true RMS voltage range: 0.1 V to 750 V.
• Stated input limit: 1000 V DC and 750 V AC maximum between INPUT HI and INPUT LO.
• Stated category: Measurement Category II up to 300 V. Not for CAT III or CAT IV circuits.
• Check before buying: the category for your work, the warm-up time, and whether you need the scanner or interface options.

What the DMM6500 measures

The DMM6500 reference manual, Keithley document DMM6500-901-01 Rev. C dated April 2026, lists the measurement capabilities in its Section 4. These are wide-ranging. The manual lists DC voltage from 100 nV to 1000 V and AC true RMS voltage from 0.1 V to 750 V. DC current runs from 10 pA to 10 A, and AC current from 100 pA to 10 A. Two-wire and four-wire resistance are listed from 1 Ω to 100 MΩ, and capacitance from 0.1 pF to 100 F.

The manual also lists frequency measurements up to 300 kHz on voltage signals, diode tests, continuity from 100 mΩ to 1 kΩ, and temperature measurements with two-, three-, and four-wire RTDs from −200 °C to 850 °C. Thermistor measurements are listed from −80 °C to 150 °C. A buyer who needs a meter for bench work with many functions in one unit will find this list the main reason to consider the DMM6500.

Input limits: the number that matters most for safety

The manual states that the maximum input voltage between INPUT HI and INPUT LO is 1000 V DC and 750 V AC. The earlier DMM6500 specifications sheet we opened, Rev. A dated April 2018, lists an input protection limit of 1100 V on the INPUT HI terminal, and 350 V on the sense terminals referenced to LO. These are different documents and different revisions, so use the current manual for your unit and treat the lower figure as the limit for your planning.

Input limits describe what the meter can withstand. They do not say the meter is suitable for the circuit you plan to connect. The safety category is the figure that decides that.

Safety category: read this before you connect the meter

The reference manual states that the front and rear terminals are rated for connection to circuits rated Measurement Category II up to 300 V, as described in IEC 60664. It says this range must not be exceeded, and it warns that connecting the terminals to CAT III or CAT IV circuits can damage the equipment and cause severe personal injury.

In plain terms, CAT II covers devices that plug into a wall outlet. It does not cover the main panel, a sub-panel, or a permanently wired motor. The manual also warns about high-energy circuits and says to use test leads that meet the stated requirements. Check the leads you are using against that requirement. Mains and panel work is dangerous, and panel or service work belongs to a licensed electrician. For a related read on choosing a meter, see our true RMS multimeter guide.

Warm-up and accuracy

The manual states the DMM6500 must warm up for at least 30 minutes after it is turned on, to let its internal temperature stabilize. If the instrument has been exposed to extreme temperatures, allow more time. The specifications sheet lists accuracy at 24 hours, 90 days, one year, and two years after calibration, each with its own temperature conditions. The DC voltage table, for example, shows a one-year accuracy term for each range and a separate temperature coefficient.

Read the accuracy figures for the range and time period you will use. A 24-hour figure is not the same as a two-year figure. The specification sheet we opened is Rev. A from 2018, so compare it with the current manual before you rely on any single term.

Interfaces and options

The Tektronix product page for the DMM6500 lists the reference manual and command references for SCPI and TSP commands over a remote interface. The manual’s title refers to scanning. The DMM6500 can take scanner cards, and the specifications sheet lists maximum input signal levels for scanner modules. If you plan to use scanner cards, check the maximum input signal level for the module you choose in the specification sheet, and do not assume it matches the main input limit.

We did not verify interface options, memory size, or software bundles from the documents we opened beyond what is named above. Confirm them with Tektronix for the exact model and option number you plan to buy.

Who the DMM6500 suits

From its documents, the DMM6500 is a bench and system instrument. It is built for labs, production test, and automated systems that need high resolution and many measurement functions. It is not a handheld meter for a home electrical check, and it is not a clamp meter. For a home outlet check or a car battery test, a handheld meter with a printed CAT rating suited to that circuit is usually the better fit. For the meaning of the dial symbols on a meter, see our guide to reading multimeter symbols.

How we chose

This is a model explainer, not a ranking. We read the Tektronix product page for the DMM6500 manual, the DMM6500 reference manual Rev. C, and the DMM6500 specifications sheet Rev. A. We used only figures stated in those three documents. 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 sources.

What we could not verify

• Whether the 2018 specifications sheet (Rev. A) matches the current unit. The reference manual is Rev. C from 2026, and we did not open a current specifications sheet.
• Interface options, memory size, and software bundles for each order option.
• Scanner card limits for every card in the Tektronix range. We read only the figures in the Rev. A sheet.
• Typical performance in your own setup. The documents give specifications and conditions, not measurements from your bench.

FAQ

Is the DMM6500 a true RMS meter?

The reference manual lists AC true RMS voltage from 0.1 V to 750 V. It lists AC current from 100 pA to 10 A as a measurement function.

What is the maximum voltage it can measure?

The manual states 1000 V DC and 750 V AC as the maximum input between INPUT HI and INPUT LO. The 2018 specifications sheet lists a higher input protection figure of 1100 V on the HI terminal, which is a different limit from the measurement maximum.

Can I use it on the main panel?

No. The manual states the terminals are rated for Measurement Category II up to 300 V and says not to connect them to CAT III or CAT IV circuits. A main panel is not a CAT II location. Panel work belongs to a licensed electrician.

How long should it warm up?

The manual says at least 30 minutes after power-on, and longer if the meter has been exposed to extreme temperatures.

What temperature sensors does it support?

The manual lists two-, three-, and four-wire RTDs from −200 °C to 850 °C and thermistors from −80 °C to 150 °C. The 2018 specifications sheet also covers thermocouple accuracy.

Does it measure capacitance?

Yes. The manual lists capacitance from 0.1 pF to 100 F.

Bottom line

The Keithley DMM6500 is a 6½-digit bench and system meter with a long list of stated measurement functions. Before you buy, confirm the safety category you need, which the manual states as CAT II up to 300 V, and check the input limits and warm-up time against your work. If you plan to use scanner cards, check their input limits separately.

Sources

• Tektronix, Model DMM6500 6½-Digit Multimeter manual page, tek.com (https://www.tek.com/en/tektronix-and-keithley-digital-multimeter/dmm6500-manual/model-dmm6500-6-1-2-digit-multimeter-3). Opened 2026-10-27. Manufacturer product page; lists DMM6500-901-01C, Revision C.
• Keithley Instruments (Tektronix), Model DMM6500 6½-Digit Multimeter with Scanning Reference Manual, document DMM6500-901-01 Rev. C, April 2026 (https://download.tek.com/manual/DMM6500-901-01C_April_2026_Ref.pdf). Opened 2026-10-27. Manufacturer document.
• Keithley Instruments, Model DMM6500 6½-Digit Bench/System Multimeter Specifications, SPEC-DMM6500 Rev. A, April 2018 (copy hosted on xdevs.com: https://xDevs.com/doc/Keithley/DMM6500/doc/SPEC-DMM6500A_April_2018.pdf). Opened 2026-10-27. Third-party copy of a manufacturer document. This is an older revision than the reference manual.