8508A 8.5 Digit Reference Multimeter

8508A 8.5 Digit Reference Multimeter
8508A 8.5 Digit Reference Multimeter

Reference standard accuracy and stability, in one functionally versatile, easy-to-use solution

The 8508A is an 8.5-digit resolution instrument designed specifically for metrologists. With superior accuracy and stability over a wide range of measurements the 8508A is designed to serve as a versatile precision measurement tool for calibration laboratories that must meet increasingly stringent measurement uncertainty analysis requirements demanded by ISO 17025, as well as the need for increased productivity.

With the introduction of the 8508A, Fluke Calibration has created a new product category – the reference multimeter – specifically for metrology applications. The 8508A Reference Multimeter draws upon decades of Fluke Calibration expertise coupled with our acquisition of Wavetek-Datron to deliver unmatched accuracy and stability; functionality and versatility; and ease of use.

Superior performance and accuracy… with outstanding stability

The 8508A features 8.5 digit resolution, exceptional linearity and extraordinarily low noise and stability, producing what are arguably the most accurate measurements to be had from any commercially available product today. But that’s only part of the story. Measurements must be repeatable today, tomorrow, next week, even next year. That’s why stability must be treated with the same priority as accuracy. The 8508A demonstrates 365 day stability as low as 2.7 ppm, with a 24 hour stability of 0.5 ppm, ensuring that confidence in today’s measurement can be the same as it was yesterday or last year.

Increased functionality and versatility

Metrologists need to make many diverse measurements as part of their complex duties. To achieve this frequently requires a complex array of instruments. The 8508A provides an extraordinarily broad range of measurement capability. This means you can undertake a wider range of applications, and perform most of your measurement requirements with a single instrument, providing real economies in time and money.

Easy to use

Human error and misunderstanding of measurement setups often have severe impact on measurement accuracy. Such errors are often due to impenetrable or complex user interfaces and lack of user familiarity. The 8508A’s clear control structure with Dual ParamatrixTM displays and context sensitive menus provides a transparent, logical and intuitive mechanism with which to interact with the instrument. Consistent with the philosophy of designing a product specifically for metrologists, the command and menu configuration is constructed to ensure rapid, error free access to complex measurement setups. It means that you can focus on getting the best possible results, without needing complex sequential or multi-instrument setups, or the need to perform complex mental arithmetic or math to achieve the desired result.

A multiple-measurement workhorse

The robust characteristics of the 8508A permit replacement of eight other measurement devices by one multi-measurement precision unit. The replaceable devices are:

  • multimeter
  • resistance bridge
  • voltage divider
  • null detector
  • ac/dc transfer standard
  • precision thermometer
  • ac/dc shunt resistors
  • electrometer/pico-ammeter

Voltage measurement

With DC and AC ranges from 200 mV to 1 kV, the 8508A covers all your voltage measurement needs. Full 8.5 digit resolution is available on all ranges to provide resolution down to 1 nV. Bandwidth for AC measurements extends to 1 MHz. Excellent linearity, coupled with Ratio measurement capability, means that the 8508A can replace Kelvin Varley dividers and AC/DC voltage transfer standards, improving your measurement efficiency in one simple, single box solution.

DC volts performance highlights

  • Ranges: 5, From 200 mV to 1000 V
  • Maximum Measurement: 1050 V
  • Resolution: user selectable from 5.5 to 8.5 digits
  • Maximum Sensitivity: 1 nV

AC volts performance highlights

  • Ranges: 5, from 200 mV to 1000 V
  • Resolution: user selectable from 5.5 to 6.5 digits
  • Maximum Bandwidth: 1 MHz
  • Maximum Sensitivity: 100 nV

Current measurements

The 8508A features a remarkable new current measurement system. For the first time, resistance at the input is virtually zero. This means that measurements can be much less invasive, and present virtually zero burden to the measurement points. It also offers the advantage that complex guarding schemes are now largely unnecessary, and measurements can be made more reliably, more repeatably and with greater confidence. Ranges from 200 µA to 20 A and frequencies from 1 Hz to 100 kHz, again ensure that all of your measurement needs are covered including the high currents encountered when calibrating multi-function calibrators.

Resistance measurement

With ranges from 2 Ω to 20 GΩ and resolution as low as 10 nΩ, the 8508A can truly be described as the ultimate resistance measurement system. Add to that a high compliance of 200 V and a high measurement current of 100 mA, and you can begin to understand how the 8508A can help extend the range of your resistance measurements. But performance of the resistance measurement system doesn’t end with just specifications. Attention to measurement technique helps further improve your results. For example, when making ratio measurements, the same current is forced through both resistances, and only the measurement is switched. Measurement current is reversible to eliminate errors due to thermal effects.

  • Ranges: 10Ω, 2Ω to 20 GΩ
  • Resolution: user selectable from 5.5 to 8.5 digits
  • Maximum Sensitivity: l0 n
  • Maximum Compliance Voltage: 200 V
  • Maximum Measurement Current: 100 mA

Temperature measurement

To further extend your range of measurements, the 8508A offers temperature measurement through 2, 3, or 4-wire PRT’s or SPRT’s, with a temperature range from -200 ºC to 660 ºC. With simultaneous temperature and resistance readout, ITS-90 and Callendar van Dusen Linearization’s the 8508A is an ideal tool for both temperature measurement and PRT calibration applications. As with resistance, current reversal is used to remove thermal emf errors. This greater flexibility provides the means to increase the overall range of your scope of precision measurements, and to realize better uncertainty on many of the measurements you might already perform with less than ideal equipment.

  • Two-wire, three-wire and four-wire Ohms with current reversal
  • Range: From -200 ºC to 660 ºC
  • Resolution user selectable from 5.5 to 8.5 digits
  • ITS-90 linearization
  • Readout: ºC, ºF, K or Ω

As well as conventional front input terminals, the 8508A can optionally be equipped with a duplicate set of rear input terminals. This can be invaluable in making ratio measurements, which are available on both voltage and resistance functions. They also provide the mechanism for forcing the same current through two resistances to improve resistance ratio measurements.

Summary Specifications
Voltage DC
Range:  0 to ± 1050 V
Best 1 Year Absolute Specification:  ± 3 ppm of reading
Voltage AC
Range:  2 mV to 1050 V, 1 Hz to 1 MHz
Best 1 Year Absolute Specification:  ± 65 ppm of reading
Current DC
Range:  0 to ± 20 A
Best 1 Year Absolute Specification:  ± 12 ppm of reading
Current AC
Range:  2 µA to 20 A, 1 Hz to 100 kHz
Best 1 Year Absolute Specification:  ± 250 ppm of reading
Range:  0 to 20 GΩ
Best 1 Year Absolute Specification:  ± 7.5 ppm of reading
Range:  Range: -200 °C to 660 °C
Best 1 Year Absolute Specification:  ± 2.5 m °C*
Calibration Documentation
17025 accredited report of calibration included

*Typical equivalent measurement uncertainty for 100 Ω PRT/SPRT probe at 0 °C

Model Name Description

Reference Multimeter


Reference Multimeter with front and rear input binding posts

Accessories common to all models:

Accessory Description

Transit Case

8508A-7000K Calibration Kit

8508A Calibration-support-kit for use with characterized 5720A Multifunction Calibrator


Comprehensive Measurement Lead Kit


Platinum Resistance Thermometer


Standard Platinum Resistance Thermometer


8508A NVLAP Accredited Calibration


8508A UKAS Accredited Calibration


Rack Mount Kit


Rack Mount Kit Slides

Product Manuals
application/pdf icon8508A CE Declaration of Conformity (599.98 KB)
application/pdf icon8508A Getting Started Supplement (487.19 KB)
application/pdf icon8508A Getting Started Manual (English) (753.45 KB)
application/pdf icon8508A Manuel d'introduction (French) (716.65 KB)
application/pdf icon8508A Erste Schritte (German) (724.88 KB)
application/pdf icon8508A Getting Started (Ita) (723.77 KB)
application/pdf icon8508A Getting Started (Spa) (718.47 KB)
application/pdf icon8508A スタート・マニュアル(日本語) (852.19 KB)
application/pdf icon8508A Getting Started (Chinese) (853.78 KB)
application/pdf icon8508A Getting Started (rus) (860.66 KB)
application/pdf icon8508A Safety Information (241.89 KB)
application/pdf icon8508A Safety Information (chi) (366.43 KB)
application/pdf icon8508A Safety Information (fre) (237.1 KB)
application/pdf icon8508A Safety Information (ger) (238.83 KB)
application/pdf icon8508A Safety Information (ita) (233.64 KB)
application/pdf icon8508A 安全情報(日本語) (345.23 KB)
application/pdf icon8508A Safety Information (rus) (281.58 KB)
application/pdf icon8508A Safety Information (spa) (236.05 KB)
application/pdf icon8508A Service Manual (3.23 MB)
application/pdf icon8508A Service Supplement (333.09 KB)
application/pdf icon8508A Statement of Memory Volatility (English) (17.71 KB)
application/pdf icon8508A Users Manual (2.26 MB)
application/pdf icon8508A Users Supplement (529.11 KB)
Application Notes
application/pdf iconCharacterizing & Disciplining Electrical Calibrator Instrumentation to Improve Test Accuracies & Measurement Uncertainties (154.06 KB)
application/pdf iconEstablishing Traceability for a High-Performance AC/DC Transfer Standard
application/pdf iconHow Cables and Connectors Impact Measurement Uncertainty
application/pdf iconMaximizing Your Reference Multimeter, Minimizing Measurement Uncertainties
application/pdf iconMigrating from DC Voltage Dividers to Modern Reference Multimeters
application/pdf iconPrecision in Practice: Achieving the best results with precision Digital Multimeter measurements (62 KB)
application/pdf iconPrinciples of Metrology
application/pdf iconUnderstanding Specifications for Precision Multimeters
application/pdf icon8508A Reference Multimeter Brochure (6.04 MB)
Data Sheets
application/pdf icon8508A Reference Multimeter Accessory Guide Data Sheet (1.35 MB)
Papers / Articles
application/pdf iconCalibrating Precision Multimeters Using a Characterized Multifunction Calibrator
application/pdf iconMaking Accurate DC Voltage Measurements in the Presence of Series Mode AC Signals.
application/pdf iconWatch Out for Those Thermoelectric Voltages! (Cal Lab Journal reprint) (1.82 MB)
application/pdf iconHow to Maintain Your Confidence
application/pdf iconA Poor Man’s Resistance Bridge
application/pdf icon8508A Reference Multimeter Extended Specifications (1.87 MB)
Press Releases
Ratio calibration—what’s the big deal?