Question About Negative Voltage

You're being rather silly in publishing your phone number and email address. You were told on your last post not to do that.

Reply from GE, who purchased Bently: "Basically when Don Bently designed these systems many years ago the only transistors available at that time used negative voltage."
Using mostly sinking (NPN) transistors in design may also result in greater noise reduction.

I can tell this is going to be interesting. There are going to be many great answers.

First, why would you post personal information? Have you any idea of the number of ex Nigerian Princes who visit this site? And they are the "good" guys.

Next, there is no such thing as "negative voltage" at least in our universe. Voltage is nothing more than a difference in potential. To determine which way the electrons are flowing + and - signs are used. This is a large topic in itself.

At any rate when we measure this potential using a galvanometer (center 0 analog meter)or a digital voltmeter we can determine this. When the galvanometer deflects to the left we call it negative, to the right, positive. With digital meter, a - sign appears.

If you reverse the meter leads the polarity "reverses". Therefore "positive and negative" voltages are nothing more than where the black and red meter leads are placed.

Typically the black lead is placed at "ground' potential, this could be Mother Earth, the car frame, a strip on a circuit board, chassis etc. Depending upon which battery terminal is grounded we get either positive or negative ground systems. So if we place the positive battery terminal to the chassis ground, connect our black meter lead to ground we will measure "negative" voltages on the various circuits.

Many cars up until the late 50's were positive ground. Mack trucks carried on this tradition until the mid '70's. My understanding for the Mack's decision was based on the fact that engines were easier to rebuild if configured as positive ground. The bolts and fittings had less tendency to "bond" together.

Keep in mind electrons flow in only one direction, your body doesn't care. Electrocutions have been documented as low as 28 volts.

Place two 12 volt batteries in series.

Clip the negative lead of your VOM to the point where they attach together...this you will call your "ground".

Now using your positive VOM lead, measure alternately the other two battery terminals.

You will see that you have both a positive as well as a negative 12 volt supply.

You will find that negative voltage is for use only in the southern hemisphere.

Used in the northern hemisphere, all readings are the reciprocal of the real reading, so, you'll have to turn your meters up-side-down.

Your clocks will run backwards and resistance heaters will produce cold radiation. On the brighter side, 12 V refrigerators can be used as ovens.

Hope this helps.

Still got some of that? I got Disney's Fantasy ! I'll bring the munchies, don't move !

Have you actually "studied" anything to do with electronics and electrics? You give the impression that you studied accounting!!

These questions you ask would be mostly (all to my mind and my high school physics are over 50 years ago, when transistors were the new "kids on the block" in Schools) answered if you had simply paid attention to high school physics....

I personally find it a waste of the people's time on CR4, to even ask such badly thought out basic questions.....

GO BACK TO SCOUL!!

(Misspelling intended by the way!!, just in case you think otherwise......)

Byeeeeeeeeeeeeeeeeeeeeeeee

I had an MGB roadster in 1965 through 1969; I know it was negative grounded. Most British cars of that era were negative ground. I suspect these terms are being confused here. As I remember, there was no difference relative to positive grounding used on American autos, other than the direction of electron travel. Of course, in those days, autos used generators instaed of alternators.

Not exactly:

IC power-supply pin - Wikipedia, the free encyclopedia

'59 MGA Twin Cam 12 volt Pos ground. MG Ts also.

I also had an MG:1956 MGB.

Wish I still had it.

I hated the Lucas Electric system,though.

Negative voltage is produced by a generator running backwards.

Why don't you ask Bently Nevada ? Less effort than asking here...

In addition to the GA in the #6 post I would add:

Using a (+) 10 to (-) 10 voltage range allows the Bently Nevada equipment to utilize standard PLC I/O analog input device configuration.

Supposedly using (+) to (-) voltage devices instead of current devices allows easier conversion to digital control values and better signal resolution.

OK,time for a little basic electricity 101:

Electricity is a flow of electrons.

Electrons are negative

If an atom has an excess of electrons, it is considered a negative ion

Electrons flow from negative to positive.(current flow).

(Just like heat flows from hot to cold.)

Heat will flow from a 100 degree area to a 98 degree area.And the 98 degree heat would flow toward a 97 degree area.So it is a matter of reference,not absolute temperature.

Likewise with electricity.

Electrons will flow from an area of excess electrons to an area with fewer electrons.

The one with fewer (Relatively speaking) electrons is considered positive,and the one with excess electrons is considered negative.

Vacuum tubes are voltage driven devices,and transistors are current driven devices.

Voltage was always considered to flow from positive to negative,like water.

Later electron theory and transistors actually require the opposite polarity than vacuum tubes,except of course, J-Fets,which work similar to a vacuum tube,but I will not get into that here.

(And then there is hole theory,which is another can of worms,which deals with positive charge flow) a subject for a later date.

Early six volt automobiles in the USA and England used a positive ground,which believe it or not, does reduce corrosion,very minutely.

As previously mentioned,older transistors required negative voltage,and it would be confusing to change to another system with the large installed base of instruments already in the field.

Also,as previously noted,there are advantages in noise immunity in certain situations.