Fluke 893A

Описание: Workshop Project #37 - Fluke 893A

Another meter! Well... I guess I got a bit carried away when looking for interesting models earlier this year. I hope to have something different again soon, but the queue is long and I rather needed this one for adjusting the Fluke 5100 Calibrator.

What's a differential voltmeter you ask? Well, I also didn't quite know until I got into the details of the circuitry. I just found it on ebay based on the suggested devices for the Calibrator adjustments. After looking into the block diagram and description, it was rather easy to figure out the what/why/how. I included an explanation section at the end! Be sure to check it out!

An additional word on the "common mode" specifications. The idea is that the meter can "ignore" AC inputs that are overlaying a DC signal. Most regular meters I know have an active low pass filter at bast, which is already quite an improvement - like the Fluke 8375A I had on the bench recently - but more modern meters, like my Keithley benchtop meter, only do some sort of "averaging" for that. Now that doesn't really remove noise or AC overlay, and most of the times some mixed voltage will cause running (=fluctuating) results. This meter is pretty awesome when it comes to just ignoring cyclical noise on the input. Like for the Calibrator: measuring some 10mV with 35V AC on top? No problem!

The absolute accuracy might not be as spot on as it once was, but the 1979 Zener reference is still pretty darn accurate!

Video note:
Somehow, with all the switches, I managed to not record any of the lube application this time. You can see the tube in the corner during the switch assembly but nope, no footage of me applying it. I did went through all seven of the switches!

0:00 Intro
1:20 First Inspection and Opening Top
3:30 Power Switch Sandwich / Front Panel / Bottom Cover
5:16 Rear Panel Access! / Wire Loom / Ranging "Display"
7:15 Front Panel Assessment / Meter Overview
8:28 Getting the Bottom PCB out!
10:08 Recapping!
11:00 Waver Switches (Example 1)
12:25 Meter Movement
14:18 Backpanel Info
15:57 Waver Switches (Example 2)
18:23 Resistor Network Assembly (includes: Wiring Issue)
19:50 Resistor Network Overview / Meter Mounting
20:35 PCB Connecting / Missing Brace
22:53 Case (Front Panel) Repaint
24:22 Front Panel Assembly / Binding Posts
25:38 Mounting Front Panel / Knob Adjustments
27:25 Finishing up PCBs / Handle / Shortening Bar / Donor Device!
29:00 Closing Up! / New Stickers!
29:45 Why? What? How? - Explanations!
33:20 Sample Measurement: 5V
34:20 Summary / Credits / Outtakes

Music (in order)

My Train's A Comin' - Unicorn Heads
Nine Lives - Unicorn Heads
Wrong - Dan Henig
Town of 24 Bars - Unicorn Heads
Light Expanse - Unicorn Heads

(YouTube Audio Library)

You can support me on Ko-Fi: https://ko-fi.com/atkelar
and also on Patreon:   / atkelar  
and now also here by using the "Super Thanks" feature!

Thanks to everybody who signed up already!