Strain gauge
Robert Green
measure the load changes of the floor supported by the posts?
--
Bobby G.
Robert L Bass
> basement jacking posts to measure the load changes
> of the floor supported by the posts?
I imagine someone has though I haven't. Coincidentally, there
are strain sensors that measure floor joist flexing to detect
burglars. A company called Sure Action makes them. They call
the products "Pulsors". They give off a tiny electrical current
when the joist flexes due to an intruder's weight above.
You could measure the current and build a simple circuit to
detect occupancy but it only responds to flexing -- not a static
load -- so it still doesn't solve the perennial problem of room
occupancy for HA. :(
I've used these sensors on my own jobs a few times. When
properly installed they work well. Poorly installed they won't
detect anything smaller than Mama Kass.
The company also makes processors to trip an alarm or HA system
sensing zone when it detects movement above. The main benefits
of these things are they're completely undetectable from the
protected area and they are immune to most of the things that
cause false alarms with motion or glass break detectors. The
disadvantage is they require more effort to install than the lick
'n'stick wireless motion detectors that have become standard fare
in the alarm industry.
If you want to experiment with one of these sensors let me know.
Although I don't currently list them online, I carry Sure
Action's other lines and can provide these as well.
--
Regards,
Robert L Bass
Bass Burglar Alarms
The Online DIY Store
http://www.BassBurglarAlarms.com
--
Never underestimate the power of very stupid people in large
groups.
Frank Olson
> If you want to experiment with one of these sensors let me know.
> Although I don't currently list them online, I carry Sure
> Action's other lines and can provide these as well.
See what I mean?
Robert Green
--
Bobby G.
"Robert L Bass" <sa...@bassburglaralarms.com> wrote in message
news:l6c9v1pgf138726jt...@4ax.com...
Robert Green
Yes. I see. But do you? Bob answered my question precisely and even gave
me the name of a product to look for. All *you* did was whine and whine the
way you always do. Do you know what the word monomaniacal means? Look it
up and then make yourself a name tag. You're a one-trick pony and your
single trick has grown quite stale.
Once again, your comments contribute not a single iota's worth of
information about strain gauges or anything else HA-related. All your
constant carping tells us is that you've got an ongoing vendetta against
Bass. We know that. And we don't care. What we *do* care about is you
cluttering up CHA with your constant anti-Bass BS. You add nothing to the
group except litter. At least Bob answers posted questions and clearly
identifies himself as a vendor.
--
Bobby G.
B Fuhrmann
"Frank Olson" ...
> See what I mean?
Oh horror of horrors, Bob gave someone good information and offered to help
him get something that he doesn't normally carry and help him get started
with the unit.
Boy that is such an evil thing to do.
What color is the sun in your world Frank (Vendetta against Robert Bass)
Olson?
--
Bill Fuhrmann
LionessXXX
"Robert Green" <ROBERT_G...@YAH00.COM> wrote in message
news:78CdnZYXGcQ_NGje...@rcn.net...
Here! Here! Maybe the losers will swim back down their gutters.
Dan Lanciani
| > Has anyone here ever mounted strain gauges on
| > basement jacking posts to measure the load changes
| > of the floor supported by the posts?
|
| I imagine someone has though I haven't. Coincidentally, there
| are strain sensors that measure floor joist flexing to detect
| burglars. A company called Sure Action makes them. They call
| the products "Pulsors". They give off a tiny electrical current
| when the joist flexes due to an intruder's weight above.
|
| You could measure the current and build a simple circuit to
| detect occupancy but it only responds to flexing -- not a static
| load -- so it still doesn't solve the perennial problem of room
| occupancy for HA. :(
The Pulsors I have at least claim to vary their resistance depending on
stress. The delta detection appears to occur in the processors which
adapt to the new value with a relatively short time constant. It might
be possible to do something over a longer period if you could factor out
various non-occupancy-related noise, though thermal changes in the structure
to which the Pulsor is attached could be a big problem. Given the phenomenal
signal processing power that you can throw at a problem for relatively low
cost these days (even compared to a few years ago) it may be worth looking at.
| I've used these sensors on my own jobs a few times. When
| properly installed they work well. Poorly installed they won't
| detect anything smaller than Mama Kass.
I installed one in my house to see how well they worked (very well) and
then gave several to a friend. They are great for houses with cats (and
presumably other pets). I bought a bunch more but never got around to
installing them. Now the epoxy is way out of date. :(
| If you want to experiment with one of these sensors let me know.
| Although I don't currently list them online, I carry Sure
| Action's other lines and can provide these as well.
Do you happen to know whether they sell replacement epoxy packs or
specify a brand/type that is suitable? (See my complaints about
current hardware store epoxy elsewhere...)
Dan Lanciani
ddl@danlan.*com
Robert L Bass
> stress. > The delta detection appears to occur in the processors which
> adapt to the new value with a relatively short time constant.
Thanks, Dan, you're right. They don't generate a current as I
erroneously stated.
> It might be possible to do something over a longer period if you
> could factor out various non-occupancy-related noise, though
> thermal changes in the structure to which the Pulsor is attached
> could be a big problem...
There's more to it than that. The resistance change is momentary
and occurs when the joist flexes. It returns to its previous
state once the joist stops moving. In short, they detect a
moving load on the floor above. They do not report the existence
of a static load.
> Given the phenomenal signal processing power that you can
> throw at a problem for relatively low cost these days (even
> compared to a few years ago) it may be worth looking at.
I wouldn't discourage anyone from researching possible solutions
to the problem of occupancy sensing. However, before starting it
helps to understand the limitations of the sensors themselves.
These devices detect joist movement. A small kerf is cut into
the joist and the detector is cemented in place under that cut.
When the joist flexes the detector is stretched, causing a
momentary electrical change. It's not like a pressure switch
that closes when you stand on it and opens when you leave.
Also note that the sensors can't tell in which direction a load
is moving -- into or out of an area. They only know that a load
has been placed upon the floor somewhere within a certain radius.
TTBOMK, the transducers don't differentiate between "load placed"
and "load removed."
> | I've used these sensors on my own jobs a few times. When
> | properly installed they work well. Poorly installed they won't
> | detect anything smaller than Mama Kass.
>
> I installed one in my house to see how well they worked (very well) and
> then gave several to a friend. They are great for houses with cats (and
> presumably other pets). I bought a bunch more but never got around to
> installing them. Now the epoxy is way out of date. :(
>
> | If you want to experiment with one of these sensors let me know.
> | Although I don't currently list them online, I carry Sure
> | Action's other lines and can provide these as well.
>
> Do you happen to know whether they sell replacement epoxy packs or
> specify a brand/type that is suitable? (See my complaints about
> current hardware store epoxy elsewhere...)
Almost any two-part epoxy cement should do the job. As long as
the cement is rigid -- not flexible stuff like RTV -- it should
work fine. If you want I'll call and ask them to send you a
package to experiment with. It's been a while since I spoke to
them but the rep seemed pretty decent -- likes DIYers. :^)
Dan Lanciani
| Thanks, Dan, you're right. They don't generate a current as I
| erroneously stated.
|
| > It might be possible to do something over a longer period if you
| > could factor out various non-occupancy-related noise, though
| > thermal changes in the structure to which the Pulsor is attached
| > could be a big problem...
|
| There's more to it than that. The resistance change is momentary
| and occurs when the joist flexes. It returns to its previous
| state once the joist stops moving. In short, they detect a
| moving load on the floor above. They do not report the existence
| of a static load.
No, that is not how they work. The resistance changes when the
Pulsor is stressed. It remains changed as long as the stressing
force is applied. The detection of (only) a moving load is entirely
a function of the processor electronics.
You can see this for yourself by simply connecting a Pulsor to an
ohm meter. Apply stress by pushing the middle and pulling on the
ends. (This can be done easily by placing your thumb on the middle
of one side and your first two fingers on either end of the other
side. The two "sides" are the one with the potting compound visible
and the one opposite.) Observe that the resistance changes and remains
changed until you release your grip. Now apply stress in the opposite
direction by switching sides. Observe that the resistance changes in
the opposite direction and again remains changed until you release
your grip.
| > Given the phenomenal signal processing power that you can
| > throw at a problem for relatively low cost these days (even
| > compared to a few years ago) it may be worth looking at.
|
| I wouldn't discourage anyone from researching possible solutions
| to the problem of occupancy sensing. However, before starting it
| helps to understand the limitations of the sensors themselves.
| These devices detect joist movement.
No, Pulsors really are static strain transducers. It is the processors
which are in effect "AC coupled" (really they probably use some sort of
self-balancing bridge, though I may be abusing the terminology slightly).
| A small kerf is cut into
| the joist and the detector is cemented in place under that cut.
| When the joist flexes the detector is stretched, causing a
| momentary electrical change. It's not like a pressure switch
| that closes when you stand on it and opens when you leave.
Actually, it is a lot like a pressure switch--at least an analog
version. The real problem is that live loads typically produce
much more joist deflection than static ones. That may be the
cause of confusion about how the sensors work. I can't say whether
it is possible to pull useful static stress information from the
inevitable noise, but this would be true for any stress-based
detection approach. It is not a limitation of the Pulsor sensors.
| Also note that the sensors can't tell in which direction a load
| is moving -- into or out of an area. They only know that a load
| has been placed upon the floor somewhere within a certain radius.
| TTBOMK, the transducers don't differentiate between "load placed"
| and "load removed."
The resistance changes one way when stress is applied and the other
when it is removed. The sensors can definitely tell the difference
between load placed and load removed. Again, do not be fooled by
the fact that the processors discard most of the available information
and give you a momentary motion detect output. They are merely trying
to emulate an alarm-style motion detector to make life easy--and they
do a very good job.
Dan Lanciani
ddl@danlan.*com
Dave Houston
application but they might have an application here, mounted as the OP
suggested.
I ran the US operations of a French company that made machine tools and I
was looking for a way to sense the load on the machine (hydraulic press that
came in 30-440 ton capacity) for precise process control and to sense a hand
or finger between the dies for safety purposes. I don't recall the name of
the company (Swiss) that made the particular load cells I was interested in
but I made a trip to upstate NY to visit their US office. Their engineers
thought it quite feasible and, to my surprise, were not concerned with the
potential liability issues. I also talked to engineers at Battelle Labs and
some people from DARPA, all of whom thought it feasible. I passed the idea
along to the engineers with my company on a trip to Paris, thinking they
could follow up with the Swiss company from there. They never did, but a
couple of years later, after the US operation was sold to a former
competitor and I was consulting for them, I met with a group of engineers
(with whom they were working) at the University of Minnesota. They also saw
no difficulty in implementing it other than the need for auto-ranging
electronics to deal with the relatively small loads presented by a finger
vs. the potentially large loads presented by the workpiece.
I don't think anything came of it as the parent company (KKR) shut down the
Minnesota plant soon after that. My health had deteriorated to the point
where I had to quit traveling at about that time and had to stop working
altogether a little later.
The sensors were not terribly expensive although, in those days, the
electronics were more costly than they are now. They are certainly sensitive
enough to act as occupancy sensors although noise would be a problem as
would discriminating between a child and a pet.
Robert L Bass
> Pulsor is stressed. It remains changed as long as the stressing
> force is applied. The detection of (only) a moving load is entirely
> a function of the processor electronics.
After posting that I called an old friend who worked with me
years ago and asked about that. You are correct. My bad.
> No, Pulsors really are static strain transducers. It is the processors
> which are in effect "AC coupled" (really they probably use some sort of
> self-balancing bridge, though I may be abusing the terminology slightly).
See above response. :^)
Robert Green
> > No, that is not how they work. The resistance changes when the
> > Pulsor is stressed. It remains changed as long as the stressing
> > force is applied. The detection of (only) a moving load is entirely
> > a function of the processor electronics.
>
> After posting that I called an old friend who worked with me
> years ago and asked about that. You are correct. My bad.
I did some more web searching and found that the sensors are pretty
expensive - one mailing list suggested $100 each for a sensor and a
processing board. That's more than I wanted to spend per sensor.
http://www.sureaction.com/pulsor.htm
doesn't mention price either. I've found that's never a sign of low prices.
I want to use something like the strain gauge they use in electronic
bathroom scales. The Pulsor seems to work using a longitudinal sensor glued
to a joist that can detect deflection. I would rather have a sensor that
reported a change in resistance as it experienced an increase or decrease
from the "setup" load. Since I am refinishing a section of the basement, I
want to mount some sensors in various locations so that I can detect
increasing static loads on parts of the support structure.
--
Bobby G.
Dave Houston
transducers.
http://www.kistler.com/do.content.us.en-us?content=KistlerCountryHome
http://203.147.186.54/html/Kistler/kistler_technologies.htm#contents
Dave Houston
http://www.tekscan.com/flexiforce.html
Robert Green
news:440362fd....@nntp.fuse.net...
> Kistler Technologies pretty much wrote the book on industrial type
> transducers.
>
> http://www.kistler.com/do.content.us.en-us?content=KistlerCountryHome
> http://203.147.186.54/html/Kistler/kistler_technologies.htm#contents
Thanks for the cite. That's a lot of info to digest but from what I gather,
I'm out of luck. Piezo sensors detect deltas only up to a certain point,
and it's measured in hours.
What would you do to try to measure both a house settling and/or a serious
stress on a support column? I'm a little worried about the power chair that
dad's using. He settled on the biggest one we could find because it had the
most comfortable chair but with him in it, it weighs close to 400 pounds.
I probably should start looking to seismology because part of their mission
is to monitor tiny movements of massive components.
Back to the drawing board.
--
Bobby G.
Dave Houston
In addition to the resistive devices I cited, there's been a lot of work on
fiber optic load cells but I don't know whether you will find any
inexpensive products that you can buy. Here's a paper dealing with them in
much larger structures.
Robert Green
> You might investigate these...
>
> http://www.tekscan.com/flexiforce.html
These look great and the price is right. The output is exactly what I am
looking for. While the readings I get won't likely be calibrated to
standard engineering units of measurement, I think they'll provide exactly
the kind of information I want!
Not only that but a fourpack is $55 and an 8 pack, $99 so they are less
expensive than good PIRs.
Thanks Dave! (108) (-:
--
Bobby G.
Robert L Bass
> expensive - one mailing list suggested $100 each for a sensor and a
> processing board. That's more than I wanted to spend per sensor.
The sensors retail for about $41 in single lots. I'm not sure
you need their processor.
> http://www.sureaction.com/pulsor.htm
> doesn't mention price either. I've found that's never a sign of low prices.
That's the manufacturer. Alarm manufacturers almost never list
prices on their websites (it annoys alarm dealers who are their
customers).
> Since I am refinishing a section of the basement, I
> want to mount some sensors in various locations so
> that I can detect increasing static loads on parts of
> the support structure.
From the discussion so far, the Pulsor *might* still be what you
need.
Robert L Bass
> stress on a support column? I'm a little worried about the power chair that
> dad's using. He settled on the biggest one we could find because it had the
> most comfortable chair but with him in it, it weighs close to 400 pounds.
Robert,
Check your local building code. You may find that the floors are
designed to support 300 lbs per square foot. I seriously doubt
your dad plus his wheelchair will affect the structure.
By way of comparison, my waterbed weighed ~3,200 pounds with no
one in it when I was in college. During parties there were as
many as six people in tit, adding roughly another 1,000 lbs.
The downstairs neighbors didn't always appreciate my music but at
least we never fell through their ceiling. :^)
Marc F Hult
<ROBERT_G...@YAH00.COM> wrote in message
<6cKdndGakY8K52ne...@rcn.net>:
>Has anyone here ever mounted strain gauges on basement jacking posts to
>measure the load changes of the floor supported by the posts?
What would be the purpose? In other words, what would you do with the
information? The amount of flexing is only indirectly related to potential
beam failure so displacement data alone wouldn't tell you much.
Vibration data (displacement changing at moderate frequencies) are readily
obtained with your very own, built-in human sensors -- no electronics
needed.
We have 180-year-old floor joists that some $%#@ local yokel electrician cut
half-way through, in the middle, from the bottom to install electric oven
and AC wiring in the early 1980's. Solution to flexing of the floor was to
repair the joists. When we moved in a 900 lb table to the dining room, the
solution was to add support in the crawl space. In other words, 'assess and
address' -- no 'monitoring' needed.
My 2 cents ... Marc
Marc_F_Hult
www.ECOntrol.org