- posted on January 18, 2011, 1:15 am

What reefer scales are being printed on gauge sets most often ?

And finally - what pressure scales are used most commonly by the metric guys ? I see KPA here, KG/CM2 there, also bar and P - what's printed on 'SI' gauges ?

And they ARE 'zero referenced' like IP PSIG scales, right ? IOW, '0 KPA gauge' = 101325 Pascals Absolute, just like 0 PSIG = 14.7 PSIA, right ?

TIA.

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- posted on January 20, 2011, 3:32 am

So, guys - what reefer's are on today's Alco

What reefer scales are being printed on gauge sets most often ?

And finally - what pressure scales are used most commonly by the metric guys ? I see KPA here, KG/CM2 there, also bar and P - what's printed on 'SI' gauges ?

And they ARE 'zero referenced' like IP PSIG scales, right ? IOW, '0 KPA gauge' = 101325 Pascals Absolute, just like 0 PSIG = 14.7 PSIA, right ?

TIA.

How about a Pocket Pussy?

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- posted on January 22, 2011, 11:25 am

On Jan 18, 1:15 am, .p.jm.@see_my_sig_for_address.com wrote:

In the SI system we use Pascals. But for our service gauges we Bar.

As you say - 1 atmosphere is 101325bar.

Whereas 1 bar is 100,000 Pascals.

We speak of atmosphere as 0bar.

We use the MKSTQ system where: M = meters K = kg's S = Seconds T = Thermodynamic temperature (theta) Q = Electric Charge

Force = mass x acceleration = K M/S² Pressure = Force per area = K M/S²/M² = K/MS²

1m³ of water has a mass of 1000kg. Gravitational acceleration is 9.81m/s²

Thus the pressure per m² applied by the cube of water will be 1000 x 9.81 = 9810 Pascals

We would need 101325/9810 = 10.329 cubes of water stacked vertically to equalise with atmospheric pressure in a barometer having 1m² shaft area. But as Pascal demonstrated with his barrel experiment - the same pressure would be applied, per m² if the vertical shaft was just 1mm² which only flared at the very bottom to 1m².

But in SI we use Pascals for our calculations and then convert them to Bar for communication and analysis of fridge systems when it comes to refrigerants and water. We stay with Pascals when we are talking about air.

1" water pressure = 1000 x 9.81 x 0.0254 (mgh) = 249.2 Pascals

In the SI system we use Pascals. But for our service gauges we Bar.

As you say - 1 atmosphere is 101325bar.

Whereas 1 bar is 100,000 Pascals.

We speak of atmosphere as 0bar.

We use the MKSTQ system where: M = meters K = kg's S = Seconds T = Thermodynamic temperature (theta) Q = Electric Charge

Force = mass x acceleration = K M/S² Pressure = Force per area = K M/S²/M² = K/MS²

1m³ of water has a mass of 1000kg. Gravitational acceleration is 9.81m/s²

Thus the pressure per m² applied by the cube of water will be 1000 x 9.81 = 9810 Pascals

We would need 101325/9810 = 10.329 cubes of water stacked vertically to equalise with atmospheric pressure in a barometer having 1m² shaft area. But as Pascal demonstrated with his barrel experiment - the same pressure would be applied, per m² if the vertical shaft was just 1mm² which only flared at the very bottom to 1m².

But in SI we use Pascals for our calculations and then convert them to Bar for communication and analysis of fridge systems when it comes to refrigerants and water. We stay with Pascals when we are talking about air.

1" water pressure = 1000 x 9.81 x 0.0254 (mgh) = 249.2 Pascals

- posted on January 22, 2011, 7:04 pm

CGS = Centimeters, Grams and Seconds

MKS = Meters, Kilograms and Seconds

We use mostly the MKS system - in fact almost never the CGS system.

Temperature K is just an indication of the molecular motion energy of gas.

Force is mass x acceleration Work is force times distance.

If something accelerates for a certain time then it's final velocity is calculated by multiplying its acceleration by the time as in a x t. So if every second I went 2 meters per second faster for 10 seconds then after 10 seconds I would be going 20 meters per second faster than before I was accelerated. How far did I go if I accelerated from stand still? That would be half the area under the velocity/time curve. Because at the start I was not going any speed and at the end I was going 20 meters per second. So the distance would be the final velocity (a x t) times a half to get the average speed and then again by the time to get the distance so distance is 1/2at² so the work done, as in energy used, as in Joules, is Force x Distance = Mass x acceleration) x (1/2 acceleration x time x time) = 1/2mv² after everything has been canceled out top and bottom.

With gases the molecules can move in all directions so the average energy turns out to be 1/3mv² and so if we know the temperature in K (absolute) we can determine the average molecular motion energy of each molecule and if we know their mass we can then also determine their actual average velocity.

But in short we use the MKS system - meters, kg and seconds. So it is m then m² then m³ and so pressure, being force per area, is (kg m/s²)/ m²

MKS = Meters, Kilograms and Seconds

We use mostly the MKS system - in fact almost never the CGS system.

Temperature K is just an indication of the molecular motion energy of gas.

Force is mass x acceleration Work is force times distance.

If something accelerates for a certain time then it's final velocity is calculated by multiplying its acceleration by the time as in a x t. So if every second I went 2 meters per second faster for 10 seconds then after 10 seconds I would be going 20 meters per second faster than before I was accelerated. How far did I go if I accelerated from stand still? That would be half the area under the velocity/time curve. Because at the start I was not going any speed and at the end I was going 20 meters per second. So the distance would be the final velocity (a x t) times a half to get the average speed and then again by the time to get the distance so distance is 1/2at² so the work done, as in energy used, as in Joules, is Force x Distance = Mass x acceleration) x (1/2 acceleration x time x time) = 1/2mv² after everything has been canceled out top and bottom.

With gases the molecules can move in all directions so the average energy turns out to be 1/3mv² and so if we know the temperature in K (absolute) we can determine the average molecular motion energy of each molecule and if we know their mass we can then also determine their actual average velocity.

But in short we use the MKS system - meters, kg and seconds. So it is m then m² then m³ and so pressure, being force per area, is (kg m/s²)/ m²

- posted on January 22, 2011, 7:43 pm

On Sat, 22 Jan 2011 11:04:22 -0800 (PST), "Marc O'Brien - ACRTC"

OK. But go to southeast Asia, for instance - it'll vary from one country to the next ( as far as real-world common useage ).

And about your other 'issues' over there - this shit with using spaces instead of decimal points, and decimal points where commas are supposed to go, has got to STOP ! Before I have to come over there and start hurting people .....

I won't even MENTION pounds, shillings, crowns, stone, and that kind of shit.

OK. But go to southeast Asia, for instance - it'll vary from one country to the next ( as far as real-world common useage ).

And about your other 'issues' over there - this shit with using spaces instead of decimal points, and decimal points where commas are supposed to go, has got to STOP ! Before I have to come over there and start hurting people .....

I won't even MENTION pounds, shillings, crowns, stone, and that kind of shit.

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- posted on January 24, 2011, 1:31 am

On Jan 22, 7:51 pm, .p.jm.@see_my_sig_for_address.com wrote:

The point about margin's of error are none the less very important.

Also that people use the ± sign incorrectly too often.

10 apples ±1 tells us there is a 10% margin of error. We could have 9, 10 or 11 apples.

± 10 apples means we could have anywhere between 10 and -10 apples - a margin of 200% allowed for error - which is not what people actually mean when they say or write ± 10 apples - they may write ± 10 apples but what they mean is 10 ± some error :)

The point about margin's of error are none the less very important.

Also that people use the ± sign incorrectly too often.

10 apples ±1 tells us there is a 10% margin of error. We could have 9, 10 or 11 apples.

± 10 apples means we could have anywhere between 10 and -10 apples - a margin of 200% allowed for error - which is not what people actually mean when they say or write ± 10 apples - they may write ± 10 apples but what they mean is 10 ± some error :)

- posted on January 24, 2011, 1:42 am

On Sun, 23 Jan 2011 17:31:05 -0800 (PST), "Marc O'Brien - ACRTC"

So, how ya like DEM apples ? :-)

( NY phrase, we forgive you for not getting it ).

So, how ya like DEM apples ? :-)

( NY phrase, we forgive you for not getting it ).

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