dampp-chaser controller and its calibration

[Roger Wheelock]

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Hi Isaac,

Let me answer as many of your concerns as possible.  I will respond in =
the
text of your message.

----- Original Message -----
From: "Isaac OLEG" <oleg-i@wanadoo.fr>
To: "Roger Wheelock" <roger@dampp-chaser.com>; "Pianotech"
<pianotech@ptg.org>
Sent: Tuesday, December 10, 2002 11:53 AM
Subject: RE: DC "Smart Heater Bar"


> Thanks, for answering.
>
> Yes the question about the scrub is yet open, the 2 systems mounted
> with them, have the pads becoming scrubby and probably less efficient
> in a few months (3-4 months actually), and , as the customers are of
> the keen ones (of course they are , as they have a DC in their pianos)
> they noticed that new pads where necessary more often that what I've
> told them.
>
> What I don't really get is if the "pad"s light blink when the pads are
> dirty with the deposit, then if I relate that to the other problem I
> suspect (too much warmness near  the controller when the lights are
> on), that would mean :
> 1 =B0 The scrub develop too fast so the pads are less efficient
> 2=B0 Then the pads light is on always
> 3=B0 the warmness of the power + pads wire lights tend to give the
> controller an optimistic idea of the humidity.
> 4=B0 When humidity if too high it is then less corrected by the rods.
>
> That makes a lot of supposed problems due to initially ameliorations
> of the product.

Heat within the control unit (Humidistat) comes from small resistors on =
a
circuit board which controls all the functions of the Humidistat.  The
design is such that the small amount of heat creates positive air flow
across the sensor making it more responsive than in a passive system.  =
(By
the way we have optimized the effect in our new H-4 Humidistat for =
Grands.)
So I do not believe heat in the Humidistat is causing you a problem.

> As often in these kind of evolutions, there are some possible
> drawbacks, I hope the problem is not as a catastrophic scenario as I
> write there, but that is understandable that the 3 lights together
> induce a warming of the wiring (in Watts how much ?)anyway UNDER OUR
> 220 v 60 Hz A.C. that is the case (the box was almost as warm as a low
> wattage rod on the wire side)
>
> May I suggest that the controllers be calibrated after they have been
> on for sometime, and in a somewhat close environment as under a
> soundboard. How are they calibrated actually ? When I first plug the
> system it always work fine and react with an acceptable tolerance in
> H.R. from what I've seen yet.
>

We calibrate each sensing unit prior to the manufacture of each =
Humidistat.
They go through a state-of-the-art humidity and temperature controlled =
test
chamber for four cycles of rh =3D 30 to 65 over a 48 hour period.  If
calibration does not meet our specification units are recalibrated and
retested.

The sensors we use are chosen for their stability.  They show very =
little
drift in the field.

While calibration in a piano would be ideal, we manufacture hundreds of
Humidistats each week and such a calibration protocol would be very
expensive.

I hope this helps.

Roger




> Is there a transformer, or some thyrstor (resistances) in the
> controller ?
>
> Thanks for your help
>
> I've find another lack of security in the kind of plugs used (3 pins
> computer type) as sometime the contact is not perfect with this
> plugging, while I can't see why.
>
> That's all for my (hopefully constructive) comments. For sure I'd like
> a window in the tank to see the water level, and a customer is
> dreaming of :
> A rack that can be moved out of the piano (terrific for concert
> stages)
> An automation for the water (this is more complicated I guess as it
> involves a pump servo serviced).
>
> I wish to order a partial system too, and will check again with my
> retailer.
>
> Thanks for your help.
>
> With bets Regards.
>
> Isaac OLEG
>
>
> PianoTech
> 19 rue Jules Ferry
> 94400 VITRY sur SEINE
> FRANCE
> tel : 033 01 47 18 06 98
> fax : 033 01 47 18 06 90
> cell: 06 60 42 58 77
>
>


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