Ah yes I can see that as a possibility I'm going with ceramic bearings.
Ones that can be run dry for short periods.
-------- Original Message --------
Subject: [AR] Re: Speed sensor for pump shaft
From: "Bob Herguth" <bob@xxxxxxxxxxxxxx>
Date: Sat, November 21, 2015 4:53 pm
To: <arocket@xxxxxxxxxxxxx>
I think the best thing to do would be to try it and use an RPM meter or high
speed camera to test the hypothesis. You can use a variable reluctance
interface IC to produce a sq. wave output from your input to get a 0-5v
output. Very inexpensive and they work well.
Out of curiosity, I googled magnetized pump shaft and there are some cautions
about possible bearing damage from magnetization of the shaft.
-- Bob
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx]
On Behalf Of Monroe L. King Jr.
Sent: Friday, November 20, 2015 3:45 AM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Speed sensor for pump shaft
I think your right. From what I understand so far there is a small coil
used as
the pick-up. Once you use a magnet to magnetize the nut or the shaft the
field rotates and causes a small current in the coil.
Amplitude and frequency would increase with rpm.
I believe you would get 2 pulses per revolution? 120,000 rpm would be
2000 rps and with 2 pluses per revolution that would be 4 khz?
I am hoping to use the sound card on my computer to do signal conditioning.
The speed sensors in marine applications use an actual magnet which I'm
sure has a high field strength. I can't actually use a magnet on the shaft
but I
can magnetize the nut or the shaft.
There are 2 reasons I need the sensor. #1 is I need to know the turbine
speed so I don't overspeed during testing and #2 I need to know the
horsepower generated so I know I can reach the needed horsepower to
provide the pumps.
I can machine a disk to use as a flywheel and knowing the weight of that
disk
there are some simple programs out there to calculate the horsepower.
-------- Original Message --------referring to. They produce a signal that increases in frequency and
Subject: [AR] Re: Speed sensor for pump shaft
From: "Bob Herguth" <bob@xxxxxxxxxxxxxx>
Date: Fri, November 20, 2015 2:42 am
To: <arocket@xxxxxxxxxxxxx>
I'm familiar with variable reluctance sensors. I believe that's what
you're
amplitude
as the rpms increase. Signal conditioning is required to prevent the high
voltage produced from exceeding the limits of a uC.
-- Bob
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx
[mailto:arocket-bounce@xxxxxxxxxxxxx]
On Behalf Of Monroe L. King Jr.
Sent: Thursday, November 19, 2015 2:53 PM
To: Arocket <arocket@xxxxxxxxxxxxx>
Subject: [AR] Speed sensor for pump shaft
Anyone have any experience with a magnetic speed sensor? This type
of sensor you magnetize the end of your shaft with a permanent
magnet and the flux produced is used to get the rotational value.
