🔴 Mailbag Monday 4th November 2024 - No.1296

Mailbag Monday 4th November 2024

0:00 - Intro.
0:21 - Infinite Improbability Drive Badge (no link).
5:40 - HP/Agilent Feet (no link).
8:10 - FNIRSI HRM-10 Review: TBA
10:51 - Mystery Test Gear....
11:40 - Fluke 720A Kelvin-Varley Voltage Divider (no link).
14:00 - Waffle drool waffle droool, drooool.

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My Electronics Tools (video and purchase links)
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Heathkit IT-12 Signal Tracer.

[ivolol]

KVD divides a voltage, it's not just a big decade resistor.

Basic operation for KVD, is put 10V or 100V into its input, (or 11V into its 1.1x input instead, so it's possible to get 10.001V on output) and X% of that voltage given by the numerals will appear on the output. However because its resistance only hovers between 10-100K, it is quite low impedance and will easily suffer from a voltage divider effect; so the division is only guaranteed accurate if you are drawing no current from the output. You can do this either by supplying some very high impedance buffer, or in the traditional usage, when using it for nulling two voltages. Put a null meter between (10VRef+KVD) and an unknown voltage, then adjust KVD till nullmeter nulls, and you have the exact voltage of the unknown to read from the KVD dials.

If you have the null reading between the KVD and its unknown, it's one of the most accurate ways of doing division of an input single voltage source.

Pitfalls: just make sure to never draw any large amount of current from its output, don't short it, or the grey neckbeards in the sky will yell at you for heating up their precious virgin selected resistors.

[IanScottJohnston]

So I know who to contact now if I get another piece of HP test gear with missing feet…….LOL

[KBUIF]

Wow, you have the world supply of HP Feet !!! The price of those on eBay is ridiculous !!

[pault]

Test the 12V power supply in a real socket to confirm 100W - Which would require about 10A on the input at 12V with efficiency loss and 15 or more Watts of heat at the device.

[timballam]

You've got a really big package 😂😂😂😂😂

[p.j.wilkins]

7:32 - you'd better be purchasing more equipment to use with those feet. I know you've been getting rich off my patreon subscription for a while now 😄.

[johnbaker]

Hey I could use some of those feet for my 4263b and 4338B