## PSN-L Email List Message

Subject: Re: vertical sensor
From: ChrisAtUpw@.......
Date: Fri, 29 Dec 2006 20:07:46 EST

```In a message dated 29/12/2006, tchannel@.............. writes:

1.  I have made an adjustable magnetic  damper, which I can slide in and out
to increase or decrease the effect.   Chris, gave me a very good example of
how to adjust the damper on the Horz  Lehman, I finished a few months ago.  It
was something like, "move the  arm 10mm and release it, it should move past
center and extend 5mm past  center, it then should return to center and stop;"
Would it be the  same for a vertical spring sensor?

Hi Ted,

Correct damping is when you get ~ 0.5 mm overshoot,  NOT 5 mm, from a 10
mm deflection!

It is the same for both sorts of sensor, but the  vertical damping
usually has to be stronger - the damping force required is  inversely proportional
to the period.

2.  The coil measures 847 ohms.  If I  were to use a resistor to act as a
damper, what would the ohms value be for  the resistor?
Is there a  formula?

Yes, but it may be easier to just measure and see.  You need a closely
coupled coil with a fairly intense magnetic field. Remember  that drawing off a
damping current both reduces the output voltage and increases  the circuit
noise. The resistance also depends on the mass, the set pendulum  period and the
magnetic field. More mass - lower resistance, greater period  - higher
resistance, higher field - higher resistance.  Remember that  most amplifiers have an
input resistor which needs to be 'taken into  account'.

Regards,

Chris Chapman

In a message dated 29/12/2006, tchannel@.............. writes:
<=
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damper, which I can slide in and out to increase or decrease the effect.&n=
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Chris, gave me a very good example of how to adjust the damper on the Horz=
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Lehman, I finished a few months ago.  It was something like, "move th=
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arm 10mm and release it, it should move past center and extend 5mm past=20
center, it then should return to center and stop;"   Would it be=
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same for a vertical spring sensor?
Hi Ted,

Correct damping is when you get ~ 0.5 mm oversh=
oot,=20
NOT 5 mm, from a 10 mm deflection!

It is the same for both sorts of sensor, but th=
e=20
vertical damping usually has to be stronger - the damping force required is=20
inversely proportional to the period.
<=
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style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
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2.  The coil measures 847 ohms. =
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were to use a resistor to act as a damper, what would the ohms value be fo=
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the resistor?
Is there a=20
formula?

Yes, but it may be easier to just measure and s=
ee.=20
You need a closely coupled coil with a fairly intense magnetic field. Rememb=
er=20
that drawing off a damping current both reduces the output voltage and incre=
ases=20
the circuit noise. The resistance also depends on the mass, the set pendulum=
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period and the magnetic field. More mass - lower resistance, greater pe=
riod=20
- higher resistance, higher field - higher resistance.  Remember t=
hat=20
most amplifiers have an input resistor which needs to be 'taken into=20
account'.

Regards,

Chris Chapman
```