Very handy; appears to be very accurate.

I purchased my COM-100 meter well over a year ago, in Feb 2012, and its performance to date has been flawless. I purchased a bottle of the 1000 ppm calibration solution along with the meter. To date every test I've made of the meter's accuracy has been right on the money without a need to adjust calibration, and I'm still on the original batteries. I use this meter primarily for testing the ppm of the ionic colloidal silver I make at least monthly. I also use it for testing the ppm in my home water, hot and cold, and purified water produced by my reverse osmosis machine. The RO machine takes my home water @ 350 ppm and purifies it down to Update: 1 Feb 2014I continue to frequently use this meter for checking TDS/ppm on: faucet water, RO unit water, swimming pool water, rain water, roof runoff water, steam distilled water, and even colloidal silver I've brewed. I also purchased HM's 1000 ppm TDS test solution that I use occasionally to retest the accuracy.. I've never had to recalibrate it. This is a great test instrument that appears to be quite tough and highly accurate. I've had it almost two years and have yet to replace the battery. My recommendation is BUY IT...

Update 6/2/21Originally I gave this meter 5 Stars and from an accuracy and ease of use perspective it still deserves that rating. However, this is the third one I have purchased in just over three years. The most recent one just started displaying inaccurate readings - by a significant margin too. I know this since I had an older one and was able to verify the accuracy close enough to know something was not right. I tried changing the batteries, which really should not have made a difference, and it was still way off. The first one I had just up and died with no display. At the time I assumed it might have quit working after I dropped it once, but now I am thinking it was just defective. I am very disappointed because it is one of the best meters I could find, although at about 3x the cost of most other meters close to this price point.In the end, I would still recommend this meter if you want something real accurate, but the quality is suspect. I would think these meters should last years not months.Original ReviewIf you read some of my other reviews about the low cost ($10-$20) meters I have tried you'll know my opinion on getting a decent one. It's a crap shoot at best. Most come pre-calibrated with little if any option for re-calibrating them and when they do it's a finicky process and doesn't work very well - if at all. I was starting to lose confidence in the meters I purchased previously so I decided to pick up this one. It was recommended by a web site that I trust which specializes in indoor hydroponic growing where EC levels are critical. At this price it was a bit of a risky deal but at least worth sending back if it did not work.So far it has performed perfectly. I purchased some of the 1000PPM calibration fluid made by the manufacturer along with the meter and it tested spot on the first time I used it. I tested the two other meters I have against it and they were close, but I need better than close and the confidence it is accurate in various ranges. I feel a lot more confident using this meter.I only use it for EC not PPM, but I suspect it accurately measures PPM as well. I can tell you it tested fine for PPM using the solution. That said, PPM is based on a mathematical calculation using EC, which is the true value. So really I would recommend measuring in EC if you are measuring for salinity of nutrients for growing. For pools or drinking water, PPM is probably fine.It has multiple modes so it will measure in pretty much any scale you could want which you won't find in a low cost meter. And best of all, it can be re-calibrated. It's not an easy process, but at least it works. Of course I have not had to do that yet, but at some point I am sure I will and am confident it will test fine after re-calibration. The instructions leave a little to be desired, but they are by far the best I have seen and what I would expect at this price.The other two meters I tried and virtually all the low cost models you'll see on Amazon, are almost identical and made in China. This one is unique in that it is reportedly designed in the US and made in Korea so maybe that is the difference. If you are an indoor grower or someone who needs a dependable EC meter, I can highly recommend this unit. In my opinion this meter is worth every penny and I only wish I would have purchased this one first before I spent about $30 on two other meters that I could not trust.Note: Some of the negative reviews on this unit appear to be related to older models. I have not experienced any of the issues mentioned in those reviews and I use this meter every day.

Very good meter.The minute I recieved it,I tested every water source in and around my house.I also tested water that pass through different types of filters.I even tested ocean water and distilled water.Each test opened my eyes to incredible results.Example: I tested distilled water and got a result of 2 ppm.I put two tablespoons of pure sea salt in two ounces of same water and got a result of 990ppm.What I found disturbing was I tested sea water from a very clean and far out(about a mile off shore)place in the ocean and got an overload on the ppm scale-Also got same result in ppt scale.Which I guess either the water was filthy or salt concentration was off the scale.Every test I did was done three times and got consistant results in each case.I am very pleased with this purchase.I would recommend to anyone who wants to know what levels of ppm or ppt of dissolved solids are in there water.It is a shame that this tester cannot identify what is in the water,but that would make it a much more expensive meter.

Needed something for reading my nutes and this answered. Needs to be Calibrated before first use. I like to take both this and there PH meter and soak them first for about 30 minutes in distilled water. Then I get ready to calibrate this one easy my 7 year old nephew can do it. Showed him once and bam kids a natural okay not yet. But anyways I recommend it. Don't be scared of this is a solid instrument. As a instrument for measuring comes upkeep on anything like this follow OEM guide in the manual you will be happy too. YES MINE HOLDS ITS CALIBRATION FOR A LONG TIME. REMEMBER ITS A MEASURING INSTRUMENT THEY ALL NEED CALIBRATION PERIODICALLY. I DONT CARE WHAT EVEN A FLASK HAS TO BE CHECKED FOR ACCURACY. You get my point calibrated yes far off was mine no but don't hurt to check. Shoot I'm that happy I brought the PH meter they make ;). I haven't looked backed I wouldn't call it luck just sometimes companies do make lemons.

Much more accurate that cheap TDS meters. Temp stable. Using it for RO water and CS. Worth the price

My aquarium runs on 7GH and 2KH, this meter reads 400+TDS, my cheap ones all read 200-250, there is no way with those parameters im at 400+ TDS with weekly water changes. For that price an absolute junk item, very dissapointed.

I have been using for three months no problem at all.

Es practico y preciso me agrada que es a prueba de salpicaduras y la calidad del equipo es buena

JUSTE PARFAIT