Discussion in 'Coco Coir' started by Neverender CC, Dec 23, 2012.

1. Hi guys - I picked up a HM Com -100 EC/TDS/Temp meter but i'm having trouble figuring out which setting to use and how to read the conversion.

here's the link to the unit : COM-100: Waterproof EC / TDS / Temp Combo Meter - HM Digital
It says in the product desciption:
"Factory Calibrated: The COM-100 meter is calibrated with a 1413 ÂµS solution."

I have 8 different modes I can use to read:

-EC uS
-EC mS
-TDS ppm KCI
-TDS ppm 442
-TDS ppm NaCl
-TDS ppt KCI
-TDS ppt 442
-TDS ppt NaCl

I have also purchased both 442ppm and 1000ppm calibrating solutions.

Can anyone tell me how to determine if the meter is reading in 0.5 or 0.7 EC?

I'd like to use EC as my reading standard since I've read its the easiest but I'm a little confused at this point. If I want to read in straight EC as opposed to ppm do i need a different calibration solution?

I have done some experimental readings with my nutes and water if this helps anyone with my question:

meter setting: 442 ppm
Bottled water: 23.4
Tap: 313
50/50 mix of tap + bottled: 155

meter setting: uS EC
Bottled: 40.8
Tap: 480
50/50 mix of tap + bottled: 240

meter setting: mS EC
Bottled: 0.04
Tap: 0.48
50/50 mix of tap + bottled: 0.24

Big thanks to anyone who can point me in the right direction!!!

2. Well, I really am unsure what all those different TDS modes are.

I'm pretty sure to see if it's .5 or .7, just mix up something at 1 EC, then switch to a TDS mode and if it reads 500 it's the .5 and if it's 700 it's the .7 conversion.

You don't need a different calibrating solution. EC is electrical conductivity and TDS is total dissolved solids. In the end, they are just 2 ways to measure how much stuff is in your feed solution.

The difference between the uS EC and the mS EC is 2 decimal places.

The u is actually a micro symbol which 1 uS EC would be 0.000001 S EC.

The m stands for milli and it's 0.001.

To be honest, I don't know what the S stands for, it's some sort of measure though. The common EC would be the mS EC, where 1 mS would be around 700 ppm with the .7 conversion. Stick it on mS EC and just run with that. It's the standard that most growers use if they aren't using ppm.

3. Thanks spyro, you answered all my questions.

4. i got the exact same problem right now! same pen! do you think you could helpp me?

5. I don't measure ppm or ec but of the tests you listed, my bet is on the mS EC. People talk about like 1 or 2 ec... 1.5 ec etc. they're all the same just different conversion factors.