Hello grow community, I am starting my third grow, but my actual second grow. The first attempt was a disaster. I am also starting some clones and mother plants. Here is my situation; I have the Apera PC60 pen, it measures in COND. uS. Here are some readings that I am getting: 28.2uS, 54.2uS, and different ranges in between. So, is COND the same as EC or do I need to convert it. Some of my TDS readings are 14.5ppm to 39.5ppm. Any thoughts, suggestions or ideas would be greatly appreciated.
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A conversion chart such this may help you:
This may not be the best choice for your situation, just the first example that came up.
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I have a question about scale 500 or 700 scale. I have heard someone on here explain it to someone as " we use 500 scale in US it’s easier". Well it becomes a big difference when your explaining things in ppm when you get up around 1000 to 1200 ppm. I use the 700 scale personalty. But I think there is a lot of confusion with less experienced growers. I guess ypu gotta know your nutes and how higher ppm affects plants. But i have seen where people will talk about using ppm like 300 more than i use with same nutes. I think to myself it must be different scale. If i explain I always try to state EC not ppm or if i saw ppm I clarify 700 scale. Having the chary that shows EC along with 500 and 700 scale.
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Perhaps somebody that is more knowledgeable will weigh in.
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I found a chart online that shows EC, 500 and 700 scales. It is very useful for me when i didn’t totally understand. I still use it as a quick reference sometimes. Just talking out loud i guess.
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@TMan72 perhaps this link will answer your questions.
What are the different conductivity scales? What do they mean?
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That’s a good read @merlin44 , I think all newer growers should read that to fully understand and grasp. As we know messing up ppm or EC on the high end can destroy a plant rather quickly. Thanks dude
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Thanks for the information and the link. It was throwing me off by TDS readings I was getting. I went into the Apera book and it was set at the 700 scale. Also the EC readings didn’t show up on any of the charts I looked at. Thanks again @merlin44.
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Thank you for the tag @merlin44
PPM and EC TDS it all can be confusing. However, it’s actually very simple.
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I’m assuming you’re in the United States of America. We use the 500 scale for our PPM/TDS and we use EC ms/cm
For EC it’s ppms PPM X 2
Example
100 PPM = 0.2 EC (or 200)
1000 PPM = 2.0 EC (or 2000)
EC simply uses the decimal system
See, it’s so very simple. Now one thing you might want to do just to be on the safe side is email your nutrients manufacturing company and ask them if they’re feeding chart is 500 scale for their us feeling charts. One would assume that it is. But it never hurts to be safe as you’ll want to know are you using the correct scale when it comes to nutrients
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One last thing to point out. If you’re using a 700 scale because you’re not in the US and you’re seeking assistance on this forum (which is a US website and we primarily use the 500 scale) you might want to clarify it in your initial posting so there’s no discrepancies.
HAPPY GROWING my friends 
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morning @TMan72 … yes that is the same measurement… you must slowly swirl your meter in your solution until the reading stabilizes…sometime you have to remove the meter from the solution and put it back in but it will give a stable reading … now once you get the stable reading go to the ppm scale and now multiply the EC reading by .5 and/or .7 and which ever one matches the ppm reading tells you which scale your pen is using…
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I also use Aprea it comes set on the 700 scale but you can change it to 500 scale 
I just got one today a GS4, mine wasn’t set on 500 scale. But all i did was click the mode button again it cycled right to 700 then click again back onto PH. Haven’t played enough but if there is a way to set it, it didn’t appear that way. But as i said i still gotta do some reading, so far i think its a good meter.
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Sorry for the delay, I am in the US and as it checked out, my Apera pH was set to 700 scale. What was throwing me off was when I got a reading of 51.3 and a TDS reading of 37.2 . When I changed it to 500 scale I was getting some readings of 12.8mS and a TDS reading of 6.5 ppt. Looking at the EC charts I saw that they all pretty much stop at 32 EC. I think that was why I thought COND and EC were different. However, after your post and some further research, a light bulb clicked. Thank you for you help.
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@TMan72 hey grow bro, what model meter do you have? A pic would be good too. I accidentally purchased an Apera meter that was not the right model for hydro growing, can’t remember the model it was blue. I exchanged it got the GS4 and all the headaches went away. No ppt crap or converting EC etc. All your need to be concerned about really is PH, EC and ppm. Make sense
Good luck
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Yup that’s the one i ordered by mistake. I called there customer service about a strange EC i was getting. After telling her what i was using it for, she said oh our GS4 model would be much better suited for that. So i returned it and got the GS4. Wow much easier to use and read. Luckily i got it from amazon. It is like $30 more but well worth it in my opinion. Plus it was only like $170
Good luck dude
@Fritz what is the difference between the GS4 and the PC60? What growing medium are you using? I went to a soil coco mix and it looks like I’m fighting a pH issue. I flushed the plants and my run off pH was anywhere from 5.8 up to 6.7. I noticed 3 days after flushing, some leaves look to be showing signs of pH issues. After flushing I watered with recharge and Fox farm Bloom and some CalMag, the ones with grow dots, I feed with recharge and CalMag.
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