Math help

[biferi]

I have a Math Q/A if you can help with?

I know it I say 20mV I move the point 3 places to the left and write it as .020 Volt.

And if I have 35mV I move the point 3 places to the left and write it as .035 Volt.

But if I have 4000mV and I move the point 3 place to the left I get 4. Volt.

Is this right?

 

[KeepItSimpleStupid]

Yes.

Shortcut: Ohms law. R=V/I; You can use any two K ohms, mV and mA and get units of Volts, Amps and Ohms.
From V=IR (1A*1000 ohms) gets the same result as 1000 mA*1K ohm (1 *1000); Unit of volts.

Sometimes it's just easier to write 10 mA and enter it as 10e-3 etc. You really don't have to worry about moving the decimal place just enter it in "Engineering Notation" where the exponent is a multiple of 3. mA, uA, nA, pA and aA. I don't expect you to know atto-amps 1E-15 amps) but you should be able to remember -3 (milli), -6 (mico), -9 (nano) and -12 (pico)

 

[biferi]

OK because if I have 35mV I write it as .035 and I can see the 3 places after the point so I know it is Milli.

But when you have 4000mV and write it as 4. Volts how do you know it meens 4 Milli or 4 Peco or anything?

What I meen is if I see .035 I can see it is in the Milli but if I just see something that says 4. I do not know what it is?

What am I not getting?

 

[KeepItSimpleStupid]

I can put as many leading zeros before a number and it does nothing to the value of the number, so 4 can be

000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000004.

Same with trailing zeros for 4.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

You have to memorize the prefixes, but you KNOW that they are multiples of 3.

What I meen is if I see .035 I can see it is in the Milli but if I just see something that says 4. I do not know what it is?

that one is easy to spot, but 1e-5 (-.00001) is not. It's also 10e-4 0.000010 and 100 e-3 which is 0.000100

I didn't actually do any conversions.

Doing nothing is an oversimplification for now.

But when you have 4000mV and write it as 4. Volts how do you know it meens 4 Milli or 4 Peco or anything?

it's more context, convenience or application than anything else. My boss once said we like things to be between 1 and 10. Over simplification. Thus 10 Billion miles and not 10 with a lot of zeros.

In one measurement I was involved in. 1e12 was effectively the same as 3E12, but it would not be if it were currency.

 

[KeepItSimpleStupid]

This might help a bit: (took me a while)

[latex]\frac{4\: \mathbf{V}}{\: }* \frac{1000\; mV}{\mathbf{V}}[/latex]

This is basically something you need to learn how to do and it can go on and an to get to the unit you want. So, say by knowing basic conversions, you can convert miles to cm just my using the proper fractions. They can be used upside down if needed. The object in the end is to have the units cancel. I've made the V's in Bold and those unots will cancel, leaving mV as the final unit because I know that 1000 mV = 1V,

So, I "CONVERTED" 4 V to Millivolts by knowing that 1000 mV = 1 V

So, knowing that there are 5280 ft in a mile, 12 inches per foot and 2.54 cm per inch, you can convert miles to cm. Arrange the fractions such that the units cancel.

x miles * 5280 ft/1 mi * 12 inches/1 ft * 2.54 cm / 1 in; The answer will be in cm.

You need to do this will any problem with units. Some units like ampere can be alternatively coulombs/sec.

So, it's showing how to convert 4 or anything written in Volts to mV. Volts is what's know as a basic unit,

EDIT: Added unit conversion example.

 

[crutschow]

OK because if I have 35mV I write it as .035 and I can see the 3 places after the point so I know it is Milli.

But when you have 4000mV and write it as 4. Volts how do you know it meens 4 Milli or 4 Peco or anything?

What I meen is if I see .035 I can see it is in the Milli but if I just see something that says 4. I do not know what it is?

What am I not getting?

Showing the units.
You should write it as 4V not just 4 to define what units the 4 is referring to. Otherwise it could be 4 of anything.

 

[Scotophor]

Showing the units.
You should write it as 4V not just 4 to define what units the 4 is referring to. Otherwise it could be 4 of anything.

Also, if it makes you feel better to see the decimal point, write it as: 4.0 V

 

[ericgibbs]

Same with trailing zeros for 4.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

If it is a 'nominal', 5V then no decimal point is required.

By adding extra trailing zero's you are inferring that the 5V is no longer a nominal voltage,
eg1: 5.0V infers its accuracy is to one decimal place
eg2: 5.00V infers the 5V has a required accuracy of two decimal places.

Do not add trailing zero's unless you want to advise the reader that a higher accuracy/stability of the 5V is necessary, which is sometimes required, for say a reference voltage.

E

 

[KeepItSimpleStupid]

I didn't want to add that yet, 5, 5.0, 5.00, and 5.000 represent more precision just as 5 mV, 5.00 mV and 5.000 mV do.

Eric, it's not accuracy, but precision. https://en.wikipedia.org/wiki/Accuracy_and_precision

Accuracy is more of a how your meter agrees to a standard. Precision is how close you can measure. I didn't want to get into this yet.

Electronic datasheets are for devices called Precision references not Accurate references. e.g. https://www.google.com/url?sa=t&rct...7Mvjua8oXRKdolA&bvm=bv.82001339,d.eXY&cad=rja

 

[ericgibbs]

Hi Kiss,
I often see statements in technical literature that says, eg:
The reference voltage setting/reading must be accurate to with 1mV, IMO precision is how precise its possible able to set a parameter.
I would say that both ways of expressing the parameter are in common usage, so either definition is understood and acceptable to most engineers.

E

 

[ericgibbs]

Duplicated due to slow response of ETO

 

[cowboybob]

Hey, Eric,

The "Like" is for your seasonal avatar .