EC/TDS meter questions

d42zero

Well-Known Member
Hi,

I purchased a cheap TDS meter from eBay to check my nutes... the 2.76 storage solution arrived today so I thought I would test readings and I got some weird results. The solution is 2.76 millisiemens/cm and the meter reads microsiemens/cm so it *should* read 2760μS/cm in the storage solution (at 25degC according to the label), but it reads a little over 3000 at exactly 25degC. It reads much lower than this at lower temperatures; is it normal for the temp to make a huge difference? Readings at 19degC were down around 2000.

PPM reading was 1088 at 19degC and almost 2000 at 25degC which doesn't line up with any conversion charts.

There seems to be no option to calibrate this meter.

Is there an explanation for this or have I just got myself a crappy dud meter?

Thanks
 
pick up an apera ec60 if you can swing it. insanely good ec/tds meter. can be calibrated and comes with the fluids to do it. laboratory grade meter. absolute best bang for dollar in it's category. apera also makes cheaper meters, but they just won't compare, stick to the 60 series if interested.
 
Thanks for the info guys, I'll start looking for a new pen. The Apera one looks good and seems available for about a hundred bucks which isn't a big deal if it's decent and is going to last a long time, so I might pick one of them up.

Got another issue with plants developing little spots and stuff but I'll put that into another thread
 
The upper end meters temperature-compensate.

Didn't have the dollars for that unfortunately, but I did get a HM COM-80 which is the next step up from the cheap eBay rubbish... bottom of the range but from what seems to be a quality manufacturer and MUCH better made than the first one I got. It displays the temperature alongside the reading so that makes life easier, I can just pop the solution in the microwave for a few seconds then wait until it cools to ~25deg and I'm off.

Something I've noticed is that between about 20 and 30 degrees celsius the reading doesn't change a lot, but it does seem to drop dramatically if the temp of the water is below 20degC... I ran a couple of tests with 2.6EC calibration solution and it read spot on 2.6 from about 30deg down to about 21-22deg, then it started to drop off.. at 19deg it was reading 2.2 and 18 it was reading 1.9. Might run some more tests but for now I think just making sure it's not super cold should be enough.

If this grow does well I'll probably invest in a really good combination pH/EC meter, my pH pen is also a super cheap one but it does allow me to calibrate it so it's a bit more reliable than the first EC pen I got (which couldn't be calibrated). It'd be nice to be able to do it all in one measurement though :)
 
Didn't have the dollars for that unfortunately, but I did get a HM COM-80 which is the next step up from the cheap eBay rubbish... bottom of the range but from what seems to be a quality manufacturer and MUCH better made than the first one I got. It displays the temperature alongside the reading so that makes life easier, I can just pop the solution in the microwave for a few seconds then wait until it cools to ~25deg and I'm off.

Something I've noticed is that between about 20 and 30 degrees celsius the reading doesn't change a lot, but it does seem to drop dramatically if the temp of the water is below 20degC... I ran a couple of tests with 2.6EC calibration solution and it read spot on 2.6 from about 30deg down to about 21-22deg, then it started to drop off.. at 19deg it was reading 2.2 and 18 it was reading 1.9. Might run some more tests but for now I think just making sure it's not super cold should be enough.

If this grow does well I'll probably invest in a really good combination pH/EC meter, my pH pen is also a super cheap one but it does allow me to calibrate it so it's a bit more reliable than the first EC pen I got (which couldn't be calibrated). It'd be nice to be able to do it all in one measurement though :)
I've got a HM PH-100 which seems pretty consistent and has a replaceable tip. For EC I have a Bluelab Truncheon.
 
i have a hm com 300 all in one as well. ec/tds/ph with a replaceable probe. great meter but the probe tip alone is double the cost of an apera 60 series stand alone. when the ph probe side broke i got an pera ph60 series and liked it so much i got the ec60 when i set up a second space.
 
I've got a HM PH-100 which seems pretty consistent and has a replaceable tip. For EC I have a Bluelab Truncheon.

Ah I looked at the Bluelab Truncheon but don't have the time to build a second garage to store it in, it's huge :laughtwo::laughtwo: It was also really expensive locally, maybe $200 or so.

i have a hm com 300 all in one as well. ec/tds/ph with a replaceable probe. great meter but the probe tip alone is double the cost of an apera 60 series stand alone. when the ph probe side broke i got an pera ph60 series and liked it so much i got the ec60 when i set up a second space.

Hmm I'll look more into them. They're a little hard to find locally, I could've splurged for an EC60 instead of the HM but would've been waiting a week or two for international delivery and I needed something fairly urgently. I do like the way the Apera has the clear cap for taking the measurement though, I suppose I could measure in the caps in my pens but the clear cap would make that super easy...

The Apera combo (PC60) is roughly the same price as the HM COM-300 so if the tips are much cheaper I think I'll look into one of those instead. How long did it take for your tip to fail?
 
The Apera combo (PC60) is roughly the same price as the HM COM-300 so if the tips are much cheaper I think I'll look into one of those instead. How long did it take for your tip to fail?

the PC60 combo meter here is roughly two and a half times the cost of the ph60 or ec60 stand alones. i went with the stand alones. the tip on the hm com300 combo meter was about the same price as the stand alones.

the ph tip on the hm com 300 bust about 6 months after purchase. i still use the ec/tds side. the ec/tds tips on any meter never breaks, you only have to worry about the ph bulb. i picked up two spare ph tips for my apera meters and never looked back. replacement tips for any combo meter seem to be prohibitive here.

on top of everything else it is almost impossible to find a replacement tip for the hm com300 in canada. at present i can't even source one on the big river site.
 
the PC60 combo meter here is roughly two and a half times the cost of the ph60 or ec60 stand alones. i went with the stand alones. the tip on the hm com300 combo meter was about the same price as the stand alones.

the ph tip on the hm com 300 bust about 6 months after purchase. i still use the ec/tds side. the ec/tds tips on any meter never breaks, you only have to worry about the ph bulb. i picked up two spare ph tips for my apera meters and never looked back. replacement tips for any combo meter seem to be prohibitive here.

on top of everything else it is almost impossible to find a replacement tip for the hm com300 in canada. at present i can't even source one on the big river site.

Oh wow really? Amazon has the EC60 for US $93 and the PC60 for US $115 so I was thinking if I'm going to mail order something internationally then the combo would be the way to go. In hindsight I really should've just ordered the PC60 instead of getting the COM-80 locally but I just needed something quickly... it was here in 24hrs and is doing a good enough job for the moment.

Interesting to know about the tips, I've tapped my pH meter on the sink a few times by accident while shaking it off and got a bit worried I'd break it! Good info, I'll make sure to factor in the tip cost when I eventually upgrade.

Thanks for all the info! :)
 
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