The tiniest of caveat for people thinking of doing a DAQ for the first
time: loadcell amplifiers and pressure transducers have bandwidth
specifications, and they're often much lower than what you can get the A/D
to do. So while you can capture the signal at 20khz (40ksps/2), there's a
good chance that there's only 100 Hz of actual data in the loadcell and a
few khz in the pressure transducer. (And 5Hz would be incredibly fast for a
thermocouple amplifier.)
That can be used to your advantage for reducing noise, in that oversampling
and averaging is an effective way to increase the precision of the
measurement. Basically trading resolution on the X axis for resolution on
the Y.
If you ever need 10khz of real data, you have to have that spec in mind
through the process, and it leads to strange pressure transducers and tiny
accelerometers.
This part is currently a stretch if you're not a computer person, but
loading the data into a time series database like Timescale or Influx and
then doing your data analysis in Grafana can make that process fairly quick
and repeatable, as you can configure the averaging in an interactive plot,
and also do things like integrating vs. time to get total impulse. An
Arduino or analog shield feeding data into a Pi running that software is
fantastically powerful. You could use that idea as the data visualization
side to launch an orbital rocket from practically another country, for
example.
On Wed, Feb 22, 2023 at 8:55 PM Terry McCreary <prfesser@xxxxxxxxxxx> wrote:
Cheaper, maybe. Easier...I don't think so. Dataq's starter units require
no programming. None. The free WinDaq software is quite versatile and has
worked well for me for 25 years. I use a DI-1100 right now ($80 but out of
stock; damn chip shortage). It's powered from the computer's USB, has
12-bit precision with four differential inputs. Using just one input
permits up to 40ksps---literally almost 100 times faster than I use for
routine thrust measurement. No auxiliary parts needed, no wiring other than
connecting to the load cell amp or other transducer---and they supply both
the USB cable and a screwdriver. Don't even need an enclosure.
I guess it depends on how you want to spend your money and your time. And
on the value you place on your time. The time I've saved by using a turnkey
product that cost as little as the Dataq units was definitely
worthwhile---for me. However, for those who enjoy working with an Arduino,
the time spent setting up the unit may not be objectionable.
Terry
------------------------------
*From:* arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> on
behalf of Ramizcan Umut Seckin <Rocketry101@xxxxxxxxxxx>
*Sent:* Wednesday, February 22, 2023 10:39 AM
*To:* arocket@xxxxxxxxxxxxx <arocket@xxxxxxxxxxxxx>
*Subject:* [AR] Re: Subject: Re: S-26.500 KNSB Sugar Shot test tomorrow
Troy,
Isn’t it easier using an Arduino laying around (also cheaper) instead of
the DataQ module?
I never tried transducers before, do you need to make a hole in the bulk
head or can it be done without (used load cells till now)?
Last question is it possible to just use a transducer in order to make a
impulse graph?
Raum
On 21 Feb 2023, at 22:47, Troy Prideaux <troy@xxxxxxxxxxxxxxxxxxxxx>
wrote:
John,
Seriously, you can pick up a cheap Chinese transducer up for not very
much at all these days eg:
https://www.aliexpress.com/item/4000704177712.html?spm=a2g0o.productlist.main.37.36306a5c49iiuO&algo_pvid=8e31b2f2-0268-4b88-aa52-48ab4ca50125&aem_p4p_detail=202302211321284979106786310800001783306&algo_exp_id=8e31b2f2-0268-4b88-aa52-48ab4ca50125-18&pdp_ext_f=%7B%22sku_id%22%3A%2210000006206659883%22%7D&pdp_npi=3%40dis%21AUD%2124.09%2122.89%21%21%21%21%21%40211be59e16770144882715524d06f7%2110000006206659883%21sea%21AU%21100784320&curPageLogUid=jwiSi6bY02xM&ad_pvid=202302211321284979106786310800001783306_19&ad_pvid=202302211321284979106786310800001783306_19
and a basic DataQ module for $50 which you shouldn’t lose in a mishap
https://www.dataq.com/products/di-188/
Not much investment provided you have a PC to run it with or even some
flight electronics have the capability to log additional data channels.
Craig Strudwicke’s old flight computer was one example of that. In fact, my
multimeter does data logging.
I mean, for **candy** motors, you generally don’t worry, but for
something this size – as you would know, there’s a fair bit of work in
producing something on this scale irrespective.
Troy
*From:* arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> *On
Behalf Of *John DeMar
*Sent:* Wednesday, February 22, 2023 6:29 AM
*To:* arocket@xxxxxxxxxxxxx
*Subject:* [AR] Re: Subject: Re: S-26.500 KNSB Sugar Shot test tomorrow
Ken,
The one thing it may tell us with some certainty is that the cause
wasn't the hardware. Even with an aluminum case, it should have held 1500
psi. But, it would be helpful to see the retaining ring, to see if it's
intact or sheared or rolled.
Regarding the instrumentation, burn time plus success is good enough for
the relatively low cost of this motor. The loss of any sensors and related
equipment could exceed the investment in the test article.
-John DeMar
Las Cruces, NM
https://www.linkedin.com/in/jsdemar/
On Tue, Feb 21, 2023 at 12:02 PM roxanna Mason <rocketmaster.ken@xxxxxxxxx>
wrote:
Other than the test video, without any instrumentation, post test hardware
inspection (and speculation) will be all you can do to conduct your
analysis.
One channel minimum of Pc, chamber pressure, trace would be helpful. Even
an analog pressure gauge on video would give
at least a low frequency reading and maybe give the failure pressure...
Posting some pics of the post test hardware would give more eyes on the
subject and more chances of zeroing in on the overpressure mechanism.
Ken.
On Tue, Feb 21, 2023 at 8:25 AM John DeMar <jsdemar@xxxxxxxxx> wrote:
Rick,
From those specs on the case and screws, I get about 2800 PSI to shear
the screws (derate grade 8 tensile strength by 50%). Assuming 1/4" wall
standard-grade oil pipeline steel, the case should have deformed the holes
at 2000 PSI and sheared at 2400 PSI. High grade pipeline steel would shear
at 3000 PSI. I didn't derate for temperature based on the short time to
heat soak.
So, plenty of margin on the hardware for a normal operating pressure in
the 1000 to 1500 PSI range.
-John DeMar
Las Cruces, NM
https://www.linkedin.com/in/jsdemar/
On Mon, Feb 20, 2023 at 7:18 PM Rick Maschek <dmarc-noreply@xxxxxxxxxxxxx>
wrote:
The case was approximately 12 inch by 9 feet long, quarter inch wall oil
pipeline steel pipe.
24 grade 8 half inch bolts in two rows holding the quarter inch wall steel
retaining ring.
The forward bulkhead was a steel plate welded in the motor case.
5 grains of KNSB propellant 20 inch long with the cores varying from 2.5
inches at the bulkhead to 4 inches at the nozzle
We used aluminum motor cases as our mandrels covered in silicon sheet
and greased for release.
The nozzle grain weighed in at 124 pounds with the others slightly heavier
because of smaller cores.
The nozzle had a 94% ideal density, normal density for me is 96-98%
I was up all night Thursday and much of Friday night helping student teams
so I left soon after our 12 inch test.
Not sure what caused the anomaly, lots of speculation and guessing. I'm
still investigating the cause.
We had two previous successful 12 inch KNSB sugar tests, one with 2 grains
and one with 3 grains.
This test had five grains and was designed to be progressive to test our
three piece safety nozzle.
Design pressure at start up was higher than the two previous 12 inch tests.
Flew a 4 inch KNSB motor just a couple hours before the 12" test UCLA
Rocket Project Avionics & Recovery test
<https://www.youtube.com/watch?v=jWspWbTCXbM>
<~WRD0000.jpg>
UCLA Rocket Project Avionics & Recovery test
https://www.youtube.com/watch?v=jWspWbTCXbM
Rick