On 10/2/2010 2:57 AM, Neville Munn wrote:
Oh, I think I see. I would have thought that if one meter which has
resolution increments of '.1' shows a reading *higher* than '1.', then
the meter which reads in increments of 1 would display 1 instead of
000 when the first meter registers higher than 1 initially?
That is true generally. But when you add in accuracy it might still give
a zero, if for instance it has an accuracy of .5 and thinks the water is
reading .4 because it is off .5 on the accuracy.
If that's your "...water which is 0.4..." thing then I'll have to do
some reading up.
Example: My records show the Com100uS reading has to exceed 2.6
before the ComTDS3 reading moves from 000 to 001ppm
That makes sense. 2.6 on uS will be equivalent to 1.3 on the TDS, and
if the accuracy is no better than .3, than that is quite possible.
.
As most meters are set up or calibrated taking a water temperature
compensating factor into account, would this also have a bearing on
the apparant different readings from one manufacturers meter to another?
It can, that would reflect in the accuracy or precision/repeatability.
Meaning, not only the calibration fluid used, but also the built in
temperature compensation may have an influence on the reading of a uS
meter compared to a ppm or TDS meter as stated above?
Yes, the calibration fluid and water being tested need to be at the same
temperature.
Example: My records show the ComTDS3 *always* shows a higher water
temperature of DW straight from the bottle anywhere between
1 to 1.8 degrees compared to the Com100uS meter, is the aforesaid an
explanation for that?
A constant offset should not be that significant in being a problem as
long as both are calibrated and used at the same temperature.
Curiously, after EIS/CS production that temperature difference in the
majority of cases seems to reduce after the solution has been in
storage for a while, like down to 1 degree or lower, I find it rather
strange that it doesn't remain the same difference as it was straight
from the bottle.
It is quite possible that aggregation is endothermic (in fact if you
have two particles colliding that stick together, then you will have
less kinetic motion, and thus possibly a reduction in temperature).
Marshall
N.
> Date: Fri, 1 Oct 2010 23:14:28 -0400
> From: mdud...@king-cart.com
> To: silver-list@eskimo.com
> Subject: Re: CS> Distilled Water of .000
>
> On 10/1/2010 9:16 PM, Neville Munn wrote:
> > OK.
> >
> > Not that I'm overly concerned with meter readings particularly but
> > here are some figures if they are of any value.
> With some of these one could certainly get 0, since they lack the
> resolution to measure less than 1. For water which is 0.4 of what they
> are measuring they would measure:
> > ..
> >
> > Com ec/tds/temp...resolution ec 0-99: .1uS, 100-999: 1uS
> > #I don't use the tds function.
> 0.4
> >
> > Com tds3...range 0-9990ppm (mg/L)
> 0
> >
> > Hanna tds1...range 0-999ppm (mg/L), resolution 1ppm
> 0.
>
> That is why it is so important to know what the resolution is when
water
> is highly non conductive. I do my measurement with a meter that has a
> resolution of .1 uS, and thus have never seen 0. If I were to use one
> of the other meters I would see 0 all the time, but they would not
> really be 0, just lower than the resolution of the instrument.
>
> Marshall
> >
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