# Homework help - Transmitter for dP

Discuss Homework help - Transmitter for dP in the Industrial Electrician Talk area at ElectriciansForums.net

#### teafour

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Hello.

I've got a last homework before the summer, which is due to be handed in tomorrow.
The question is the following:

"How is it possible that a normal transmitter, used for measuring differential pressure, can get the label FT, PT, LT in a process scheme?"

Of course, the labels stands for Flow Transmitter, Pressure Transmitter and Level Transmitter.

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#### Bobster

Nothing like leaving things to the last minuet.

I presume you're referring to a P&ID diagram with the prefixes FT,PT,LT?

All 3 reading can be calculated from differential pressure.

#### teafour

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Haha, agree! Actually this was due to monday next week (we got the homework yesterday) but due to changes in our schedule, the homework was moved to being due tomorrow morning.

Yes, you’re correct.

In what specific way can you calculate? I’d need to be more specific.

B

#### Bobster

Ok, you'll have to do some digging into the formulas but look at:

FT - Example, ducting with a water pump, measure pressure between a restriction at the outlet of the pump. With the cross sectional area of ducting and pressure you can calculate flow. If I remember correct google Bernoulli's equation and it should give you the equation

PT - well that's obvious, its a pressure transmitter.

LT- Had this in a thread this week. Measure the pressure of say, water in a tank compared with atmosphere. 10bar = 1m of water.

#### teafour

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That really helped me out. Big thanks to you Rob!

#### Devonchris

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I'm sure Rob means

10m of water = 1bar pressure.

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#### Bobster

I'm sure Rob means

10m of water = 1bar pressure.
I do indeed, it's only Tuesday an has already been a long week!

#### Rigpig

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Do a search for "lessons in industrial instrumentation" pdf. All the info you require plus more will be contained in here. It is open source and constantly updating....

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