tds vs. conductivity

I read with interest the threads over the past while regarding tds and conductivity meters...Alot of people recommended conductivity, but unfortunately i couldn't find one with an adapter in my city, and i didn't want to do mail-order....so i got a TDS meter to be difficult...
I was thinking the .5 scale was inaccurate because my tap water reads at 320 TDS so that would make the conductivity over 600!! I've bred angelfish in that water so it just wasn't adding up...
So, anyways i went over to Dave_C's place today to check out his new fish from Cary and took my meter...Measured with my meter, measured with his conductivity meter...his reading was exactly twice my reading...
So, to make a long story even longer, at least in the case of my TDS meter, the reading is exactly one half of what the conductivity is...

i'm glad my arguments were right all this time....lol

thanks for the factual verification

[Steve_Warner]

Hi all,
David, it's interesting you mention this. I was speaking to our resident Chemist at my work who runs our R/O Plant(he taught College Chem classes for 17 years before this) about this subject. I had brought in my Myron-L R/O meter for him to calibrate and I learned that different equipment Mfgr's use different conversion factors in acquiring their readings(which matters when using calibration fluids). My Myron-L used a factor of .8 I believe he said, but Hach uses a factor of .5, if I remember correctly. This was all very interesting to hear, as I was wondering from all the discussions on here and elsewhere. I think I got those numbers right, but this was the basic message of his "lesson for the day" with me. I love to pick this guy's brain, as it has so much knowledge, it is a joke what he knows! I can tell he LOVES to talk to me about the subject and always invites me to his shop to talk Chemistry(very tempting proposition, as I could spend days just rappin' Chem!). I will go chat with him again and write this down so I get it straight and repost the info here! By the way, if anyone comes to Vegas, this gentleman owns a restaurant in a small strip casino and is there nightly to run the place. He told me to come on down(for business, I'm sure) and he'd fill my brain with some good knowledge! 16oz Porterhouse dinner for $11.95!

Steve