Re: TDS Tester and in-line meter

amelliahona <no_reply@...>

Hi Ian:

I believe your error on your TDS meter upon startup is due to High TDS (i.e. high EC,
electrical conductivity) due to TDS CREEP. See my post # 2062 dated March 13, 2006 for
a discussion on TDS Creep. It takes my system about 60 seconds running at pressure
for the EC to recover from the TDS Creep and come down to about 400-450
microSiemens/cm where it stabilizes during the run. Certainly intermittent testing of TDS
is better than nothing but I really like the security of knowing from minute to minute that
the EC is within acceptable limits. The Omega EC monitor sounds an alarm at an EC level
that you can set. I set my at 800 microSiemens/cm.

Besides the EC meter installed about six inches downstream from membranes I also
installed a valve and short hose just prior to the product water line entering the copper
pipe that empties into the fresh water tank. I can take water samples here also to verify
with my hand held TDS meter.

TESTING THE DESSALATOR EC sensor. The Dessalator circuit board has an oscillator
circuit on it that I would guess from previous posts supplies 400 hertz low level AC
voltage to the sensor and measures the EC of the product water. I tested my system as
follows: I took the sensor out of the piping and immersed it in a cup of fresh water. The
system started up, changed over at the one minute mark to a green light and good quality
indication and produced water. At that point I poored sea water into the cup with the
sensor in it. Using my hand held TDS meter I verified that the TDS of the water in which
the sensor was immersed was greater than 10,000 ppm. The system did not alarm and
continued to produce water. I waited for 10 minutes with it in this mode to see if there
was a timer function to prevent transient high TDS from prematurelyl shutting down the
system but for at least ten minutes the system continued to run without diverting the
water or indicating poor quality water. I then shut the system down and let it rest for 30
minutes. Then with the sensor still immersed in the salt water sample I started the system
up normally. It started exactly as before, at one minute green light, water production
starts and continues. So in neither situation did the sensor and associated circuity
recongnize "bad quality" water and function appropriately.

See my previous posts related to lack of documentation on the circuity or a coherent
explanation of how the system is SUPPOSED to work. Joel shares our frustration with
Dessalator and is indeed having trouble with the NEW Dessalator system on his 54. I have
written to Jean Jacques Lemonier regarding this issue and Olivier Beaute has responded to
me in a timely, professional and detailed fashion. I am awaiting a few clarifications from
Olivier and then will summarize what I have found. I stand by my suggestion to all Amel
owners with Dessalator systems that they should install an independant EC monitor
(preferably a continuous monitor). Amel remains the finest company I have ever done
business with.


Gary Silver Amel SM 2000 Hull # 335 Lying Sea Cow Bay, Tortola, BVI

Hi Roy,

Would you please let me know if you have successfully installed your inline
TDS meters? I installed one immediately after the outlet from the membranes
on my 160 l/h unit and it came up with an error message after a second or so
I suspect that the flow rate might have been too high there as the meter
worked when the output hose was connected taken off the copper pipe that
goes to the tank and the water allowed to pass through the sensor fittings.
That's too low down to mount the meter in the galley, so if you find a
location higher up that works, then please let me know.

There have been several promises from Rod Boreham and Joel for a
clarification statement on exactly what protection there is against bad
water polluting our one and only water tank, but to date I have seen nothing
published. The fact that no reassurance has been forthcoming gives me an
uneasy feeling. It's time the record was put straight. If the protection is
not there, then there is a potentially dangerous situation for those of us
who rely upon the integrity of our water tank for long distance passages.
The facts must be known to Desallator, so why have they not come forwards to
defend their design? It's time we knew whether the salinity probe does what
we all hope it will do, or not.

Several have suggested that shorting the probe contacts will test it's
function. I am told that this is not so as the probes are subjected to a 500
Hz alternating voltage and so shorting them does not simulate a high
salinity content.


Ian Shepherd SM 414 'Crusader'

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