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Re: [Phys-L] really using a barometer to measure heights at a construction site



His not this quote from the ad an oxymoron?

". . . connected together by a wireless 30-meter cord . . ."

I was confused by this at first too. The cord is a tube containing a fluid. There is no wire inside of it. The base and measurement units are, in fact, communicating wirelessly.

--Brent

---
Brent Barker, Ph.D.
Teaching Support Manager
Department of Astronomy & Astrophysics
Department of Geophysical Sciences
The University of Chicago
Office: KPTC 314
Phone: 773-702-8323
Pronoun: He

The opinions expressed are my own, and they do not necessarily represent the views or opinions of my employer.

________________________________________
From: Phys-l <phys-l-bounces@mail.phys-l.org> on behalf of Bob Sciamanda via Phys-l <phys-l@mail.phys-l.org>
Sent: Sunday, July 29, 2018 2:35 PM
To: PHYS-L
Cc: Bob Sciamanda
Subject: Re: [Phys-L] really using a barometer to measure heights at a construction site

His not this quote from the ad an oxymoron?

". . . connected together by a wireless 30-meter cord . . ."

Bob Sciamanda
Physics, Edinboro Univ of PA (em)
treborsciamanda@gmail.com
www.sciamanda.com

On Sun, Jul 29, 2018 at 2:59 PM, John Denker via Phys-l <
phys-l@mail.phys-l.org> wrote:

No, this is not a joke or a parable; it's a real-world
measuring instrument, in many ways easier to use and more
informative than a laser level:
https://www.laserlevelhub.net/zip-level-pro-2000-review/

I betcha most students have never seen such a thing.

Although the basic idea is not new, it became a lot more
practical with the advent of cheap, highly sensitive MEMS
(micro electronic mechanical system) pressure sensors.

This is typical of real-world R&D:
a) You have to understand the need (convenient, accurate,
robust job-site altimetry).
b) AND you need to understand the basic physics.
c) AND you need to know what sort of technology is
available to connect (a) to (b).

Understanding the physics is always necessary but rarely
sufficient.

===

As a side-benefit, this provides a nontrivial non-smart-alecky
answer to the infamous barometer question:
https://en.wikipedia.org/wiki/Barometer_question

==============

Note that the specifications quote the isothermal accuracy:
http://ziplevel.com/i/4529ZIPLEVELPRO-2000Specifications-ENGLISH-
2012.pdf

The word "isothermal" is doing a lot of work in that
statement.

An interesting homework exercise might go like this:
Estimate the systematic error incurred in the following
situation: The cord is draped over a 10m high wall.
The true elevation difference (between the base unit
and the readout) is essentially zero. Because one
side of the wall is facing the hot sun and the other
side is in the shade, there is a 10 °C temperature
difference between the upgoing and downgoing parts
of the cord.

�� sun
+++++
+ WWW +
+ WWW +
+ WWW +
+ WWW +
+++ WWW +++
base wall readout
unit

====

For extra credit, design a device that is comparably easy
to use but at least an order of magnitude more robust
against nonuniform temperatures.

Hint / giveaway: US patent 5517869A
https://patentimages.storage.googleapis.com/4f/80/b1/
5bd762722e4d06/US5517869.pdf

I have not seen such a device for sale, but the idea
seems sound.


For small additional extra credit: What is the pressure
in the tube at the top of the wall? Did you notice this
potential problem? This is not a problem for the instrument
as sold. Why not?

This is also typical of real-world R&D. After you've got
the basic idea figured out, there are dozens of nuisance
issues (some big, some small) that need to be dealt with.
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