Embedded Systems Conference
Breaking News
Comments
Oldest First | Newest First | Threaded View
cookiejar
User Rank
Author
reliability?
cookiejar   11/27/2013 12:48:47 PM
I assume the idea is to locate a load cell in the tip of a screw to measure force. 

Having worked with load cells, I found the major design challenge using load cells was to keep them from being overloaded and going into plastic deformation.  Just the thought of a applying a tightening torque to a screw makes me cringe as that would twist the delicate load cell structure.  If you build in a mechanism to stop rotation between the two ends of the load cell, the stop friction will affect your readings. 

Trying to do all this in the extremely limited room at the end of a screw would be a challenge as I've always thought of screws being less than 1/4" in diameter and bolts being 1/4" and larger.  But I suppose that may have been lost in translation.


Stephen_M
User Rank
Author
Re: reliability?
Stephen_M   11/27/2013 2:35:11 PM
NO RATINGS
A bolt is used with a nut to hold things together. A screw can be used without a nut; ex: sheet metal and wood screws, self tapping, self drilling screws.

vvc0
User Rank
Author
Re: reliability?
vvc0   11/27/2013 6:07:51 PM
NO RATINGS
Hmmm, many bolts don't have nuts, such as lag bolts (self tapping), and head bolts (inserted into a tapped hole in an engine head), to name a couple. Also, screws can have nuts, such as machine screws, and even sheet metal screws with tinnerman nuts. The differentiation is more based on the diameter than the fact it is used with/without a nut, but even this is somewhat nebulous.

prabhakar_deosthali
User Rank
Author
Re:
prabhakar_deosthali   11/28/2013 6:50:02 AM
NO RATINGS
To ascertain that the screws are not overstressed while tightening them,  one can use the torque screw drivers where you can set the maximum torque that will be applied to the screw while it is tightened.

That will eliminated the possibility of the built-in sensor getting damaged by the screw tightening action.

vapats
User Rank
Author
Re: torque
vapats   11/28/2013 8:39:39 PM
NO RATINGS
Torque is not a proper measure of screw/bolt tension;  you must measure the actual elongation (stretch) of the fastener.


Torque is a mere (and often highly inaccurate) approximation.

 

RJHonders
User Rank
Author
Re: reliability?
RJHonders   11/29/2013 4:59:44 PM
NO RATINGS
CookieJar, you hit the nail on the head. Hard to put sensors in small screws and get the signals out.

ROV ENG
User Rank
Author
Instrumented Fasteners
ROV ENG   12/1/2013 11:15:13 AM
NO RATINGS
It's not difficult to put a strain gauge into the center of fasteners as small as 1/4" in diameter, we were doing this in the early 80's using proprietary techniques. The sensors were sealed inside the fastener and were suitable for use underwater. The two issues that limited widespread use were the cost and the reduction in strength of the fastener for smaller sizes. This only works for bolted fasteners unless you have a very well defined parting line between the two joined structural elements, which is where the sensor must be located. Accuracies of 0.1% were routinely achieved. Most customers were not so interested in measuring the tension in the fastener during installation, although that was useful information, they were more interested in measuring forces during operation of the machine.

Per ASME B18.2.1, a bolt is designed to be inserted through a hole and secured with a nut, while a screw is designed to be used in a threaded hole—sometimes along with a nut.



Top Comments of the Week
Like Us on Facebook

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)
EE Life
Frankenstein's Fix, Teardowns, Sideshows, Design Contests, Reader Content & More
Max Maxfield

My Mom the Radio Star
Max Maxfield
Post a comment
I've said it before and I'll say it again -- it's a funny old world when you come to think about it. Last Friday lunchtime, for example, I received an email from Tim Levell, the editor for ...

Bernard Cole

A Book For All Reasons
Bernard Cole
1 Comment
Robert Oshana's recent book "Software Engineering for Embedded Systems (Newnes/Elsevier)," written and edited with Mark Kraeling, is a 'book for all reasons.' At almost 1,200 pages, it ...

Martin Rowe

Leonard Nimoy, We'll Miss you
Martin Rowe
5 comments
Like many of you, I was saddened to hear the news of Leonard Nimoy's death. His Star Trek character Mr. Spock was an inspiration to many of us who entered technical fields.

Rich Quinnell

Making the Grade in Industrial Design
Rich Quinnell
16 comments
As every developer knows, there are the paper specifications for a product design, and then there are the real requirements. The paper specs are dry, bland, and rigidly numeric, making ...

Special Video Section
After a four-year absence, Infineon returns to Mobile World ...
A laptop’s 65-watt adapter can be made 6 times smaller and ...
An industry network should have device and data security at ...
The LTC2975 is a four-channel PMBus Power System Manager ...
In this video, a new high speed CMOS output comparator ...
The LT8640 is a 42V, 5A synchronous step-down regulator ...
The LTC2000 high-speed DAC has low noise and excellent ...
How do you protect the load and ensure output continues to ...
General-purpose DACs have applications in instrumentation, ...
Linear Technology demonstrates its latest measurement ...
10:29
Demos from Maxim Integrated at Electronica 2014 show ...
Bosch CEO Stefan Finkbeiner shows off latest combo and ...
STMicroelectronics demoed this simple gesture control ...
Keysight shows you what signals lurk in real-time at 510MHz ...
TE Connectivity's clear-plastic, full-size model car shows ...
Why culture makes Linear Tech a winner.
Recently formed Architects of Modern Power consortium ...
Specially modified Corvette C7 Stingray responds to ex Indy ...
Avago’s ACPL-K30T is the first solid-state driver qualified ...
NXP launches its line of multi-gate, multifunction, ...
Radio
LATEST ARCHIVED BROADCAST
EE Times Senior Technical Editor Martin Rowe will interview EMC engineer Kenneth Wyatt.
Flash Poll