Why So Many Units?

would be quite odd with a gauge the reads in Bar with a psia/psig legend

speak the same language? On this ventilator I am find many ways of expres sing the same pressure and flow rates.

really. People just like to use different units.

Torque units are equally frustrating. According to SI it is supposed to be Nm. I am always converting Nm, Ncm, ft-lb, in-lb., oz-in., etc.

We are also a chemistry lab. Concentration units...grrr! This is worse. U nits can be mass-per-volume or number-per-volume. Depending on the industr y we are serving, the preferred units are different. It gets a bit obnoxio us constantly converting mg/mL to nanomolar (for instance). Since our soft ware analysis needs everything in molarity, I am often scrambling to find t he molecular weight of this that and the other thing. And that is just the metric units!

Always makes me chuckle when somebody says Americans don't understand metri c. We understand metric just fine, we just also happen to know a bunch of other units and know how to convert between them.

ld speak the same language? On this ventilator I am find many ways of expr essing the same pressure and flow rates.

d really. People just like to use different units.

be Nm. I am always converting Nm, Ncm, ft-lb, in-lb., oz-in., etc.

Units can be mass-per-volume or number-per-volume. Depending on the indus try we are serving, the preferred units are different. It gets a bit obnox ious constantly converting mg/mL to nanomolar (for instance). Since our so ftware analysis needs everything in molarity, I am often scrambling to find the molecular weight of this that and the other thing. And that is just t he metric units!

ric. We understand metric just fine, we just also happen to know a bunch o f other units and know how to convert between them.

One atmosphere of pressure is 101,325 Pascals metric.

Torque is in units of Joules

The Ohm is events per second.

ld speak the same language? On this ventilator I am find many ways of expr essing the same pressure and flow rates.

d really. People just like to use different units.

be Nm. I am always converting Nm, Ncm, ft-lb, in-lb., oz-in., etc.

Units can be mass-per-volume or number-per-volume. Depending on the indus try we are serving, the preferred units are different. It gets a bit obnox ious constantly converting mg/mL to nanomolar (for instance). Since our so ftware analysis needs everything in molarity, I am often scrambling to find the molecular weight of this that and the other thing. And that is just t he metric units!

ric. We understand metric just fine, we just also happen to know a bunch o f other units and know how to convert between them.

As far as I'm concerned, getting the units right is part of the job. My 'learning units' story involves making an impedance line for a helium flow cryostat. I made a factor of ten error in the pressure (Pascals to atm. IIRC) and made the impedance x10 greater than necessary (or wanted!) Since the flow impedance 'recipe' involved cramming some wire into a thin SS tube. I wasted a lot of time making the wrong value of flow impedance. And ~$100 1980 dollars (20 liters) of liquid helium, discovering my mistake. I was younger then :^)

George H. I like ft-lbs when torquing head gaskets and such.

LOL!

d really. People just like to use different units.

Yeah, I'm trying to put together a document that starts with units of measu rement of several sensors and document the path to the ADC reading so we kn ow exactly what our range needs to be and what we achieve. People keep get ting in the way of this by mucking with the units but also saying we should enter the full range of a sensor instead of just the range we are required to measure. Meanwhile we have a problem with adequate resolution at the l ow end.

Design by committee is not always fun.

This is about a flow measurement which in the commercial unit is specified as SLM, standard liters per minute. We seem to prefer the unit of ml/s.

ld speak the same language?

still. Sm^2... standard square meters.

I think it's 1.3 HP per kW, no? That's an easy one if everyone agrees on w hat a HP is. I'm happy rating my car in kW. :)

The inch measure of pressure was from the method of measuring it, with a column of water or mercury. That's easy to understand, but very awkward for the exact reason SI units were developed, to get rid of most conversion coefficients.

ould speak the same language? On this ventilator I am find many ways of ex pressing the same pressure and flow rates.

eld really. People just like to use different units.

o be Nm. I am always converting Nm, Ncm, ft-lb, in-lb., oz-in., etc.

. Units can be mass-per-volume or number-per-volume. Depending on the ind ustry we are serving, the preferred units are different. It gets a bit obn oxious constantly converting mg/mL to nanomolar (for instance). Since our software analysis needs everything in molarity, I am often scrambling to fi nd the molecular weight of this that and the other thing. And that is just the metric units!

etric. We understand metric just fine, we just also happen to know a bunch of other units and know how to convert between them.

So does a torque of 1 Nm do 1 joule of work in a radian of rotation?

Got me on that one. How does that work?

It's the cross-section area of a long thread of fuel that you car can use to follow without losing speed. Ours does better than 0.1mm^2 only on the highway, approximately a 0.25mm diameter thread of fuel. That doesn't seem like much.

For electric cars, the measure is newtons, the force required to maintain velocity against drag. Even for gasoline cars, that would be more instructive, with a separate efficiency measure for the engine.

Clifford Heath.

One of the UK's highest pressure gas pipelines is near me. But alas there is no mains gas in the village at a domestic usable pressure.

By sheer coincidence it is about 20% off being an atto Parsec (~3cm). (recommended tongue in cheek SI rule of thumb measure one April fools)

Newton is not useful since it will vary hugely over speed and only be usefu l to compare cars directly while saying nothing about what you really care about, cost.

What really matters is $/mile or ?/mile, etc. Since the cost of el ectricity varies widely the energy per mile is useful as joules/mile or mor e commonly, even if not SI, kWh/mi. Of course these numbers will be relate d to driving patterns, but not the huge, direct impact that newtons suffer, just the same smaller effect we are used to with MPG.

A measure that would be similar to your newton number would simply be kW. This will relate more to useful units that can be used to find energy consu mption and cost. I love mashing the accelerator and watching the kW meter run up to 400 in my car.

Oh yeah, my car needs 1.25 amps at 240 V to run on the highway at 60 MPH (9

ful to compare cars directly while saying nothing about what you really car e about, cost.

electricity varies widely the energy per mile is useful as joules/mile or m ore commonly, even if not SI, kWh/mi. Of course these numbers will be rela ted to driving patterns, but not the huge, direct impact that newtons suffe r, just the same smaller effect we are used to with MPG.

This will relate more to useful units that can be used to find energy con sumption and cost. I love mashing the accelerator and watching the kW mete r run up to 400 in my car.

(97 kph) which will require a wire of about 20 gauge which is about 0.5 mm^

that's a way off, 300W is what a decent cyclist can do

a car doing 100km/h will take something like 10-15kW

Tesla3, 75kWh battery, 500km range

There is an anti-methane movement here. Several cities have outlawed gas connections to new construction, to Save The Earth somehow. They want everything to be all electric. That's going to get interesting.

The old iron gas pipes in our neighborhood were rusting out, so rather than dig up the streets and replace them they fished little yellow plastic tubes into the old pipes, ran high pressure gas through them, and put a regulator at every house to maintain the low pressure.

Here's my little units program.

I could add pressure, but we rarely deal with that.

tirsdag den 21. juli 2020 kl. 20.53.55 UTC+2 skrev John Larkin:

could speak the same language? On this ventilator I am find many ways of e xpressing the same pressure and flow rates.

ield really. People just like to use different units.

to be Nm. I am always converting Nm, Ncm, ft-lb, in-lb., oz-in., etc.

e. Units can be mass-per-volume or number-per-volume. Depending on the in dustry we are serving, the preferred units are different. It gets a bit ob noxious constantly converting mg/mL to nanomolar (for instance). Since our software analysis needs everything in molarity, I am often scrambling to f ind the molecular weight of this that and the other thing. And that is jus t the metric units!

metric. We understand metric just fine, we just also happen to know a bunc h of other units and know how to convert between them.

or just type it into google, the google calculator handle most units

uld

eam

d,

seful to compare cars directly while saying nothing about what you really c are about, cost.

f electricity varies widely the energy per mile is useful as joules/mile or more commonly, even if not SI, kWh/mi. Of course these numbers will be re lated to driving patterns, but not the huge, direct impact that newtons suf fer, just the same smaller effect we are used to with MPG.

W. This will relate more to useful units that can be used to find energy c onsumption and cost. I love mashing the accelerator and watching the kW me ter run up to 400 in my car.

H (97 kph) which will require a wire of about 20 gauge which is about 0.5 m m^2 cross section, 0.8 mm diameter.

Yes, you are right. It is 300 WH/mi I was thinking of for my X. The 3 get s more like 250 or even 200 WH/mi.

So I guess I'm going to need a bigger wire!

Oddly enough, both the consumption and vampire drain have improved as of la te. The consumption could be helped by the warm weather, but I've had the car for two years now and the improvement actually was first noticed in the early spring when it was still cold. I know they do continual updates and maybe they've improved the efficiency of the system? It used to be 333 Wh /mi was a goal and 300 Wh/mi was a really good drive. Now I can expect 333 Wh/mi and often get 300 Wh/mi and even lower. It's kinda like those gadge ts you add to your car to improve the mileage by 10-20-30%!!! The battery is down around 5-6% of original capacity, so improvements in range are welc ome.

One thing I keep reminding myself of is that the Supercharging is free to m e as long as I own the car. That alone is worth $20,000. Nice!

But that's not what people actually use. You put kWH into your battery, you get km out. The ratio of those is in newtons.

The future cost per kW is unknown when you choose a car.

People choose based on full-charge km (can it go where I need to go without a recharge) and efficiency, in kWH/km (should be n).

What *are* you wittering about? The dimensions of joules/mile is newtons!

joule = newton metre joule/metre = newton

Clifford Heath