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Sunleaves Tds Pen Help Please.


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The Sunleaves TDS Essential Digital Pen measures nutrient levels between 0 and 9,990 ppm with an accuracy of +-2 percent. Featuring data hold capability, auto shut-off, and temperature compensation, the TDS Essential Digital Pen includes batteries and is reliable for over 1,000 continuous-use hours.

 

http://www.sunleaves.com/detail.asp?sku=STD500

 

Specifications:

 

Hold function: Saves measurements for convenient

reading and recording.

 

Auto-off function: Meter shuts off automatically after

10 minutes of non-use to conserve batteries.

 

Dual Range: Measures from 0-999 ppm, with a resolution of 1 ppm.

From 1,000 to 9,990 ppm, the resolution is

10 ppm, indicated by a blinking 'x 10' image.

 

Accuracy: ±2% of each scale. The first scale is 0-999 ppm,

the second scale is 1,000-9,990 ppm.

 

Battery: 2 x1.5v (button cell)

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If everyone would just stick to EC, the growing world would be a better place. No more "is it .5, .64, .68, .7? "

 

very very true........... but some patients do not have the money for expensive EC meters (like the woman i was helping) and choose to use the cheaper tds. or a combo ph/tds/temp.

 

edit:

maybe we will all start using EC meters after they get rid of the metric system and the euro :)

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very very true........... but some patients do not have the money for expensive EC meters (like the woman i was helping) and choose to use the cheaper tds. or a combo ph/tds/temp.

 

edit:

maybe we will all start using EC meters after they get rid of the metric system and the euro :)

 

Took another look on Ebay, EC meters are now offered at about what I paid for a simple TDS meter just a short time ago. Am going to order one so can be on the same page with out any conversion worries.

 

http://cgi.ebay.com/HM-Digital-AP-2-EC-C-F-Conductivity-Meter-Tester-EC-3-/230414787145?pt=LH_DefaultDomain_0

 

Good Day :)

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good post taj :)

 

i run a couple "constant combos" so i am out of the loop i guess :)

 

the person in need traded a couple clones for it and had no clue.............. neither did i at first :)

 

but, with no calibration solution and no immediate answer from the board i dropped the good old 8-16 lucas in some r.o. water and it came out with my answer :)

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DECRYPTING EC/TDS METERS

 

there are 4 different types of meters that measure nutrient concentration, two are EC meters and two are TDS meters

 

of the 2 types of EC meters, (electrical conductivity), one displays with decimal places, the other without

 

for example

EC 2.0 and EC 2000 are the same

 

TDS meters come in 2 types, .5 and .7 conversion.

 

You seem to have a .5 conversion TDS meter

 

TDS meters take the electrical conductivity value that is measured internally by the meter (EC), but then multiplies the EC by a factor, either .5 or .7

 

so for example,

2000EC * .7= 1400ppm but also

2000EC * .5= 1000ppm

 

TDS is a strange beast and does not react logically, as you have found

 

for example 0-8-16 should read 1000ppm on .5 conversion meter, in RO water, but strangely, if you start with 250ppm water, and add the nutes, it wont necessarily come out to 1250, as you have noticed.

 

the reason I think this happens is that some of the TDS in the water gets neutralized by the nutes.

 

for example, much of the TDS in water is calcium, which is of very high pH. When nutes, of low pH are mixed in, some of the low and high values cancel each other out... this is sometimes called nute lockout and is the cause of some of the sediment in a res.

 

as far as the term TDS (total dissolved solids), in contrast to the term PPM (parts per million), they are the same thing stated in different words

 

here is an example of how the terms interact

 

An EC of 2000 corresponds to a TDS reading of 1400 PPM on a .7 conversion meter.

 

imho, .7 conversion is the primary hydroponic conversion factor, but many people own meters with .5 conversion, therefore, you MUST know your conversion, to understand my TDS numbers, which are all .7 values unless stated otherwise

 

in practical terms though, what you are doing is correct, and works fine, as you know

 

the gardner should mix nutes at the known recipe rate, then take a meter reading. WHATEVER that number is, regardless if its 1000, 1400, or any other number, THAT is the TDS of YOUR nutes in Your water, on Your meter.

 

As long as you dont change water or meters, keep using the baseline number you get as the target to go back to with nute additions

 

Im loving these questions! this is turning into a very complete archive of my beliefs

 

none of these ideas are original, Ive just spent a lot of time reading and learning from others

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  • 9 years later...

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