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EC meter question
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Posted by iliketoast (My Page) on Thu, Feb 7, 08 at 22:12
| Some hydroponics guru on this site suggested I invest in an EC meter, so I took his advice. Unfortunately, I didn't think to buy the solution to calibrate it.
Question 1: Until I do buy the stuff, can I still use the meter with any hope of accuracy? So far, it has tested distilled water as 1-5 ppm for the same glass of water, my tap water is 137ppm, tap water sitting for a few days is also in the 130-145 range. Can I trust it, or should I wait until the calibration liquid arrives (which may be a while, since I haven't ordered any yet... it's 20 bucks +sh/h!)
Question 2: When mixing nutrients for the ideal TDS (much thanks to whoever posted this, should I subtract out the 137 ppm of my tap water when testing it? |
Follow-Up Postings:
RE: EC meter question
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Yes, you can trust your meter readings.
Most EC-meters need little calibration. Once every 6 months is fine, and you can make the liquid yourself if you have access to a lab scale. It's just some salt and distilled water. |
RE: Tap water reading
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| Forgot to mention . . . Yes, you must subtract the tapwater reading. That bit of hardness in the water(Ca + Mg) becomes part of your nutrient. |
RE: EC meter question
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| Great. Thanks for the help! |
RE: EC meter question
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| Where did you get your EC meter from? |
RE: EC meter question
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| I bought this one. It was about $55 after s+h. It's quite cheap relative to others, and comes with batteries, but it's not clear how I'll be able to change them out when they die, since it seems to be a solid unit. Here's a picture. 
Oh well, I'm sure it will last a few years anyway. |
RE: EC meter question
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| A different brand but it looks very similar to my pH meter. Probably made by the same manufacturer and re-branded by others. I believe you should be able to pull the top (where the on/off switch is) out to access the batteries. Bill |
RE: EC meter question
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| greystoke, what's the math for making your own?What is the water/salt ratio?
Thanks,
mudcat |
RE: EC meter question
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| Your meter is fine. Your under 10 on distilled. Then your good. You might be off 15 points 20 at most. Who cares if your accuracy is off a little your fine. |
RE: EC meter question
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mudcat65 wrote:
what's the math for making your own?What is the water/salt ratio? I've got 577mg NaCl(dry kitchen salt) per litre of distilled water gives you 2000µS. |
RE: EC meter question
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| "I've got 577mg NaCl(dry kitchen salt) per litre of distilled water gives you 2000µS" So, .5*577mg=1000?1.5*577mg=3000? |
RE: EC meter question
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| I'm not sure I understand that formula. However, . . . I DID make a mistake. It's 925mg/L for 2000µS. NOT 577. There's NO fixed relation between ppm and µS. All depends on the type of salt in solution. For kitchen salt its about 50%. |
RE: EC meter question
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| I have a truncheon meter and love it. does not require calibration. its water proof. and it doubles as a stir stick. |
RE: EC meter question
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| Yes I got the truncheon meter becuase it doesn't need calibration - one less thing to bother with. |
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