On rockets you have lots of other ultrasonic sources (Engine, incoming
pressurant, airflow around the airframe ect.). I am pretty sure this
interferes with the sensor. Keep also in mind that speed of sound
depends on the root of the temperature of the gas (and that changes
quite during operation in a tank).
My favorites are capacitive sensors (you can use the tanks inner surface
as one of the capacitor plates), resistors on the tank wall and the
RADAR looks also good to me (depending on the dielectric constant of the
fluid. But at least hydrocarbons are ok and probably LOX as well).
Bruno
"At that time [1909] the chief engineer was almost always the chief test pilot
as well. That had the fortunate result of eliminating poor engineering early in
aviation" (Igor Sikorsky)
--
Bruno Berger
Swiss Propulsion Laboratory
E-Mail: bruno.berger@xxxxxx (HTML-Mails will be dropped!)
PGP: http://www.spl.ch/contact/Bruno.Berger.asc
WWW: http://www.spl.ch
HAM: HB9RSU
Am 16.09.2015 um 18:56 schrieb Henrik Schultz:
I have to reiterate my suggestion for using ultrasonic detection. Link
to common detector board:
http://www.amazon.com/SainSmart-HC-SR04-Ranging-Detector-Distance/dp/B004U8TOE6
ranging distance : 2cm~500 cm
resolution : 0.3 cm
which should cover just about any tank size used by folks on this list
in a foreseeable future.
Now you just have to make it work in a cryo/pressurized environment.
Make the two transducers sense through holes in the bulkhead, and let
the rest of the PCB sit outside (or in a cage at same pressure). For
$10 how much is there to lose to see if it works?
/H
------ Original Message ------
From: "Uwe Klein" <uwe@xxxxxxxxxxxxxxxxxxx>
To: arocket@xxxxxxxxxxxxx
Sent: 9/16/2015 9:44:10 AM
Subject: [AR] Re: radar fluid level monitoring
Am 16.09.2015 um 10:28 schrieb John Dom:
Uwe Klein wrote on 15 september 2015That was ~30 years ago.
a twin set of microwave doppler radar thingies repurposed from pissoirflushing activators ( you retreat and flushing advances ) arranged
in a 45°
forward and 45° backward looking setup to remove attitude influences.
The sensors where (afair) Panasonic microwave pissoir flushing
activators.
Taken apart to get at the doppler signal and arranged pairwise
looking 45° forward and back down onto the road. ( $ forward -
$backward = true forward speed )
New to me. Since you know, you have a catalog or website about such
radar
sensors, so I don't have to Google on this? Preferably with a
digital fluid
level output?
today probably two of these would work ( IANAL or the TEC equiv ):
http://www.amazon.com/SMAKN-Microwave-10-525GHz-Doppler-Detector/dp/B00FFW4AZ4
1mW ERP or thereabouts ?
Could their microwave radiation detonate N2O vapor inside its
pressurized
tank?
But it is _Doppler_ as in SPEED detection ;-)
A Level sensor would not be a proper application for these.
Maybe if the level change is fast enough to give a useful doppler
signal? Long thin tank? could work ;-)
uwe
