Fluke 8508A Reference DMM review

-h2. Contents

Intro

Slowly, but surely we are approaching to the goal of covering and describing every single 8½-digit multimeter on the market. This time it is very expensive and rare guest, Fluke 8508A. This meter was a result of facelift and update of 8½-digit Datron 1281, which Fluke done shortly after buying Wavetek/Datron T&M division on 2000’s. People familiar with Wavetek 1271/1281 units and programming language will find 8508A very similar, even in most things exactly the same. GPIB Commands are not SCPI compatible, so this meter talks it’s own language.

8508A is famous for it’s resistance performance and ability to do flexible ratiometric measurements, when equipped with extra option /01. This option adds ratio functionality and six low-thermal rear 5-way binding posts, and it does not come standard, but sold for big dollar instead. Fully featured 8508A/01 have MSRP in excess of $22K USD, making it twice as expensive to another metrology workhorse meter – Keysight 3458A.

In this article we will get familiar with 8508A/01 that was last calibrated in year 2014, and perform various test and verify it’s accuracy after all these years. Also there is very little measured data/information available online about this meter performance in respect of tempco/noise and stability for it’s main functions. To address this issue, comparison to pair of freshly calibrated Keithley 2002’s and pair of Keysight 3458A DMMs will be also performed. ACV performance will be checked against Wavetek 4920M AC Voltage Measurement Standard.

But before all that goodness, take a look on what meter have to offer us:

Measurement Function Range Best accuracy, 30 day, within ±1 °C TCAL
DC Voltage ±100 mV ±3 ppm
DC Voltage ± 1, 10 and 19 V ±1.5 ppm
DC Voltage ± 100 and 1000 V ±2 ppm
DC Current ±100 µA, ±1 mA, ±10 mA, ±100 mA ±7 ppm
DC Current ±1 A ±15 ppm
DC Current ±10 A ±20 ppm
AC Voltage 10 Hz – 30 kHz, 1 V, 10 V, 19 V, 100 V ±10 ppm
AC Voltage 55 Hz – 30 kHz, 1000 V ±15 ppm
AC Current 100 µA, 1 mA to 1A, 10 A @ 10 Hz to 10 kHz ±40 – 200, ±200 – 1000 ppm
Resistance 1-2 Ω, 10-19 Ω, 30-19000 Ω, 30-190 kΩ, 300 kΩ – 100 MΩ ±20-15, 5, 3, 5, 8-180 ppm
TrueOhm Resistance 1-2 Ω, 10-19 Ω, 30-19000 Ω, 30-190 kΩ, 300 kΩ – 100 MΩ ±20-15, 5, 3, 5, 8-180 ppm
HighVoltage Resistance 1-2 Ω, 10-19 Ω, 30-19000 Ω, 30-190 kΩ, 300 kΩ – 100 MΩ ±20-15, 5, 3, 5, 8-180 ppm

Table 1: Brief specifications for Fluke 8508A Reference Multimeter

There are different options for 8508Ф, such as:

Option ID Description
Option 01 Additional rear terminal block and ratio metric measurements functionality.
Option 90 Rack Mounting Kit
Option 95 Rack Slide Kit

As far as we know, there are no additional options available to upgrade Fluke 8508A. If you have standard 8508A and want to upgrade it to Opt.01, unit has to be returned to Fluke to perform installation of the option and recalibration.

Disclaimer

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If you willing to contribute or add your experience regarding various instruments repairs or provide extra information, you can do so following these simple instructions

As usual, all photos are clickable for high-resolution version.

Manual references

Unfortunately, there is no schematics available in public service manuals for 8508A

Thermal image captures

Firmware

Tweaks and tricks

Performance verification

Summary

This article would be impossible without work of Todd and his Model 2182 and his content and testing results. We also would like to give credits to pipelie, who helped a lot to push xDevs.com project forward. Thank you!

It’s a joy for any passionate engineer to see these instruments working, despite all those years. They might not be new and fancy with touchscreen TFTs, but still hard to replace when one need the accurate low-level measurement.

If you do have any questions, jump in comments! All the feedback is appreciated.

Author: Illya Tsemenko
Published: Aug. 17, 2018, 7:38 a.m.
Modified: Jan. 10, 2019, 7:09 a.m.

References