What does "MMM" mean in this project?

Thread Starter

Alois Luong 1

Joined Aug 15, 2019
5
Hi,

I am currently reading this experiment that was done to investigate electrostatic forces. In broad terms, it is creating a capacitor by placing two washers parallel to each other and connecting them to a power supply.

However, at one point in the procedure, it says "Use one of your MMM connected across the output of the HVPS to read the HVPS output (the right MMM in Figure 3)". I don't know what "MMM" means and wasn't able to find much on the internet either.

Here's a link to the experiment: https://ocw.mit.edu/courses/physics/8-02x-physics-ii-electricity-magnetism-with-an-experimental-focus-spring-2005/labs/experiment_ef.pdf

Here's a screenshot of the procedure:
Screen Shot 2019-09-08 at 11.19.27 AM.png

Thank you in advance!
 

WBahn

Joined Mar 31, 2012
25,066
I'm not sure what MMM stands for, but MM is likely multi-meter. I don't know if it a special type of multimeter or not. You might look at the course material for the very beginning of the course and see if they define it there.

I noticed that they mentioned using 400 V. Be careful. If that supply can deliver more than a few milliamps of current, you can quickly be talking about potentially lethal currents and more than enough voltage to push them through your body. Be sure you have read (and follow) whatever lab safety instructions they probably provided at the beginning of the course.
 

ScottWang

Joined Aug 23, 2012
6,860
Please check the page 5 of this pdf document.

The reader or student should be aware that many of the acronyms used here are not standard usage. Experiments are not numbered but are labeled with letters; power supplies are LVPS and HVPS; the analog multimeter, depending as it does on the torque on a coil in a magnetic field, is called MMM, magnetic multimeter (DMM for digital multimeter is standard).
 

AnalogKid

Joined Aug 1, 2013
8,251
I think it is a typo. In the US, a common term is DMM for Digital Multi-Meter, a digital version of the old VOM (sometimes spelled V-O-M for Volt-Ohm-Milliameter).

ak
 

WBahn

Joined Mar 31, 2012
25,066
I think it is a typo. In the US, a common term is DMM for Digital Multi-Meter, a digital version of the old VOM (sometimes spelled V-O-M for Volt-Ohm-Milliameter).

ak
Not a typo, just nonstandard usage. Scott found the document that the pages the TS linked to are extracted from and, had the TS read it (or even did a word search on it) would have found the passage that Scott quoted above. Of course it's also possible the TS only had the document for the particular lab he was trying to do.

The MMM is what the rest of the world usually refers to as an analog meter or the old VOM. They use "magnetic" because it is based on the d'Arsonval meter movement (though they don't seem to mention that name at all).

I've only scanned the document, but it looks rather interesting. There are some high voltage experiments and the kit has the student build a simple power supply that can output up to 1000 V at a current of less than a milliamp. This is used in an experiment on microwaves generated using a spark gap transmitter and the experiment has the student measure the wavelength. Maybe I'll see about working through some or all of the projects over Christmas and see if they might be worth bringing to the attention of the EE department here.

EDIT: Fixed typos.
 
Last edited:

killivolt

Joined Jan 10, 2010
742
Hi,

I am currently reading this experiment that was done to investigate electrostatic forces. In broad terms, it is creating a capacitor by placing two washers parallel to each other and connecting them to a power supply.

However, at one point in the procedure, it says "Use one of your MMM connected across the output of the HVPS to read the HVPS output (the right MMM in Figure 3)". I don't know what "MMM" means and wasn't able to find much on the internet either.

Here's a link to the experiment: https://ocw.mit.edu/courses/physics/8-02x-physics-ii-electricity-magnetism-with-an-experimental-focus-spring-2005/labs/experiment_ef.pdf

Here's a screenshot of the procedure:
View attachment 185703

Thank you in advance!

A high voltage low current will need to measure differently, however you have a high voltage high current clamp in which your wire will pass through the loops to measure your current.

Not sure if this is what your after but, a precise measurement will not be obtained unless you spend a good amount of money. If your measuring the Electromagnetic Field ok. If you're making a measurement clamp is totally different. Not sure what you're after? We need more specifics.


kv

I'll read further, but ES (Electro Static) which confused me in EMF.

The MMM is your washers.

Use one of your MMM connected across the output of the HVPS to read the HVPS output (the right MMM in Figure 3). Connect the lower washer to the low voltage side of the HVPS.
It's a typo.
 
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Thread Starter

Alois Luong 1

Joined Aug 15, 2019
5
So if I understand correctly 'MMM' means 'Magnetic Multimeter'.

However, upon researching on the internet, I couldn't find much about MMMs: there weren't any apparent pictures or online stores selling them. If this equipment is highly specialised (and/or expensive), what other equipment do you think could be used to replace it?

A.
 

WBahn

Joined Mar 31, 2012
25,066
So if I understand correctly 'MMM' means 'Magnetic Multimeter'.

However, upon researching on the internet, I couldn't find much about MMMs: there weren't any apparent pictures or online stores selling them. If this equipment is highly specialised (and/or expensive), what other equipment do you think could be used to replace it?

A.
How many times and ways does it need to be spelled out?

ScottWang tracked down the full manual for the projects you are doing, entitled "Electricity and Magnetism Experiments from Kits" and gave you a link to it.

He quoted from Page 5 of that manual where it is extremely explicit and states, "The reader or student should be aware that many of the acronyms used here are not standard usage. Experiments are not numbered but are labeled with letters; power supplies are LVPS and HVPS; the analog multimeter, depending as it does on the torque on a coil in a magnetic field, is called MMM, magnetic multimeter (DMM for digital multimeter is standard).

If the term MMM is explicitly stated as being not standard usage, why on Earth would you think that you could search the Internet and expect to find someone selling one using that term?

Why do you even need to search at all -- let along wonder if it might be some expensive, specialized piece of equipment -- when you have been told explicitly more than once that it is nothing more than an old-style analog meter, often called a VOM (volt-ohm-millamp) meter?
 

killivolt

Joined Jan 10, 2010
742
No, the MMM is NOT the washers and it is NOT a typo.
Still, there isn't enough info. MMM, is not a measurement. DMM, is but, a Measurement. But, this is an experiment. Multi bla,bla,bla,bla.

We need more info.

Typo's included.

kv

Edit/ I just want to dig deeper, but not enough info. @WBahn.
 

Danko

Joined Nov 22, 2017
849
Your analog multimeter (we call them MMM—magnetic multimeters) is a “moving coil meter” with a needle whose deflection shows and measures the torque on a current loop placed in a magnetic field. That torque is proportional to the current, and a device that measures current is called an ammeter. The multimeter consists of a cylindrical magnet (magnetized across a diameter) arranged coaxially with a cylindrical magnetic return path as shown in Figure 2.
upload_2019-9-9_13-14-47.png
In the gap is a pivoted rectangular coil; you can see the top of it if you look down into the meter. Spiral springs, top and bottom, lead current in and out of the coil and also provide a restoring torque. Jeweled bearings provide a low-friction mounting as in some watches.
 
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WBahn

Joined Mar 31, 2012
25,066
Still, there isn't enough info. MMM, is not a measurement. DMM, is but, a Measurement. But, this is an experiment. Multi bla,bla,bla,bla.

We need more info.

Typo's included.

kv

Edit/ I just want to dig deeper, but not enough info. @WBahn.
What more information do you need? The lab manual that this experiment is a part of is explicit.

From Page 5 of the manual:

Whereas in the mechanics course time and temperature are read out with digital multimeters (they being no more mysterious than a stop watch or an A to D converter), in the E&M course analog multimeters are used. Besides enforcing the reading of a scale they can be gradually understood in every detail—the d’Arsonval movement, the range switch, shunts, multipliers, diodes—in contrast to digital meters with chips and displays whose workings are hidden and harder to explain. Furthermore, low-cost digital meters, rated for 400V dc, can easily be destroyed by the over 1kV generated by the high voltage power supply. And, paradoxically, the limited selection of ranges of the low-cost analog meters is an advantage; it requires the use of external shunts and multipliers, so that knowledge of these useful topics, mostly gone from modern texts, is acquired in a natural way.

The reader or student should be aware that many of the acronyms used here are not standard usage. Experiments are not numbered but are labeled with letters; power supplies are LVPS and HVPS; the analog multimeter, depending as it does on the torque on a coil in a magnetic field, is called MMM, magnetic multimeter (DMM for digital multimeter is standard).
There is also an entire experiment (Experiment MM) devoted to the MMM and in the very first paragraph it states: "This is how your multimeter works, which we call a magnetic multimeter (MMM), in contrast to the standard term `analog’."
 
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