This link takes you to the Aeroelectric web site. You need to type Ohm meter in the google search engine, then click on the link to get the PDF. This is a booster pack that adds power to a DMM:

www.aeroelectric.com/.../LowOhmsAdapter_3.pdf

The key to interfacing the boosted DMM readout to the Op Amp is the "Zener Diode".

There is no "boost".  It is a regulated current source packaged with leads to make a 4 wire Kelvin connection.  The best part about the circuit is that it only draws power from the batteries when the probes connect across a resistance.  The range of resistances that one can read depends on how low one's voltmeter can go and how much current one can supply from their current source.  For garden variety DMMs where the lowest scale is 200 Ohms, a device like this can extend that way down.  A 100mA source will make the 200mV range on a DMM read 2 Ohms full scale.  Just be sure that circuit under test can tolerate 100mA.

Simple Variable Zener Diode:

There are several variable zener diodes available in IC market, but in Sri Lanka it is difficult to obtain variable zener diodes. (For example LM431) So I build this circuit to get the functionality of Variable Zener diode. This circuit is based on two transistors and for Q1 you can use any general purpose NPN transistor and for Q2 use any general purpose PNP transistor.

The LM431 is easier to find in America. Nice circuit though!

Can't you order parts from China?  The circuit that you show is not temperature stable.  You could fix the circuit with a thermistor and a couple of resistors, or just buy any voltage reference.  The TL431 is over 35 years old.  You should be able to obtain one as easily as any Op-Amp or garden variety transistor.

My Television's 35 years old and works fine without junk parts from China or smart alek advice from know it all punks. There's always some kind of stupid ass problem our of you. It's always some sort of trouble you make to sound as smart as smart can be. You're just a blood sucking arachnid.

Unless you are cannibalizing your TV for parts, your TV is rather irrelevant to what will get you a decent adjustable voltage reference.  Your simple circuit doesn't have any form of temperature compensation/stabilization.  TL431's are ubiquitous and almost as cheap as one or two transistors.

This kind of "Magnet Positioner" from RWG'S Levitator kit could be powered directly by a D.C. motor attached to the screw. The motor would simply have to be mounted to slide along behind the screw between ridge rails.

This video by TK shows a D.C  motor reversing from a voltage divider circuit:

https://www.youtube.com/watch?v=SUsA-YuAtBU

Rotor acceleration increases from DLE, raising flux density and Ohmic resistance in the ferrite core. The circuit senses this and backs the magnet away from behind reducing flux density in the core. This balance should permit DLE acceleration to resume.

There's a whole family of cheap "Electro-Magnetic Holding Solenoids":

Look at the minimum travel distance: Five Ten thousadths of an inch! Coupled with a maximum of four hundred forty eight ounces of pull force! That's controlling "Twenty Eight" whopping pounds of magnet force over such a miniscule distance! This looks like a winner for the small Price.

Standard Features

Reversible motion
Captive or non-captive
Unipolar or bipolar Ball bearings
5V or 12V coils
Frame size from 20 mm up to 57 mm
7.5° or 15° step angle
Linear travel per step from 0.0005" (0.0127 mm) up to 0.004" (0.1016
mm)
Linear pull out force from 8.3N (30 oz)  up to 124.6N (448 oz)

 The advantage is that a permanent magnet consumes no power when the stepper motor rests in position!

Ramset uploaded this Chris Sykes video on field cancelling coils. These kinds of coils may help reduce the flux density in the output coil ferrite core wired to a resistive load. These kinds of coils may make the stepper motor uneeded!

This an is interesting assertion from Floyd Sweett out of the "Bucking Coil" PDF, as it bears out my "Flux Density to Ohmic resistance" proportion:

"It is the Magnetic Field itself that creates drag; it creates Friction on Electric Charge itself".


https://www.youtube.com/watch?v=Z-V1z2TdQJA&feature=youtu.be

This PDF is wild too:

http://www.hyiq.org/Downloads/Guidelines%20to%20Bucking%20Coils.pdf

Here's a better picture: This coil's merely a conductor. It needs a power source and a load. It dosen't consume power like an electromagnet: The ouput coil would wrap around this coil. It would be possible to run current through this " Core Flux Density Suppressor Coil" from the output coil to a storage cap, with only minimal losses to resistance.

One simple Zener bypass diode might be all that's needed to divert current from the output coil through the core suppressor coils, simply activated by a rise in output voltage alone.

This should prolong DLE acceleration. The initial acceleration increases core viscosity and phase lag along with output coil voltage. The Zener diode, calibrated to allow current to flow at that level, begins to charge the core's "Bucking Coils". This in turn should counter core flux density and reduce phase lag to once again restore acceleration. Zener's come in escalating varieties, which would increase current flow to the suppressor coils with increasing output coil voltage. Pretty neat soloution to a formerly highly complex problem.