HM Digital COM-100 Waterproof EC/TDS/TEMP Meter

Quick summary first and full review below: Positives: Rugged design Waterproof and dust proof Batteries and lanyard included Different measurement options Calibration option Instructions in clear English Gives quick, reliable readings Replaceable sensor (although not readily/cheaply available in UK) Negatives: Screen not very large and not illuminated Instructions in small print Slightly more complicated than simple TDS meter, due to different measurement unit options (although latter is also a plus) I had previously bought a cheap TDS meter, but decided to get something a bit more reliable, as the electrodes don't last forever, anyway. I use it for plant nutrient solutions, but it would work for any liquid application. It displays as TDS in ppm or ppt (at 2 different conversion rates), mS or micro-siemens. Generally, in hydroponics, what's referred to as EC is measured in mS, or if you multiply that by 10, you get the CF value. In case you don't know (I didn't before): TDS meters measure electrical conductivity (EC) and convert that value to TDS, for which there are different conversion rates. You can look up the conversion rates in tables online. This also provides a temperature reading in C or F and automatically compensates for temperature (which otherwise affects the reading). I've not calibrated it yet, so can't say for sure how accurate it is, but am confident it's more than accurate enough for everyday purposes and readings remain the same for multiple measurements. I looked at the Essentials EC meter (only 1 review, but their ph meter has many good reviews), at a slightly lower price, and providing similar specs, but with this one, you can replace just the sensor, which you can't with the Essentials meter. However, the replacement sensor does not seem to be widely available. After a bit of searching, I found out the part # for the sensor: if you search google for "HM Digital SP-C1", you will get some results. Cheapest I saw was on ebay, sent from US, for about £25 with international tracked delivery. This is more than sturdy enough for everyday use, and has an IP67 rating (dust and waterproof for immersion up to 1 meter, though not hermetically sealed). Instructions are in clear English, easy to understand, but the writing is small. It comes in a box with plastic insert, with a ribbon lanyard that fixes to the top and AAA batteries. Measurements stabilise very quickly. The screen is not huge, and displays multiple values, but is easy enough to read with normal eye sight in good light. There's no backlight, which would have been a nice feature for poor lighting situations. Overall, am pleased with it for the price, and would recommend.

This is an excellent piece of kit that I use for drinking water measurements and hydroponics media making. It might be more expensive than other cheapo ones, but it is nice knowing this is super accurate (especially if you calibrate it to cater to whatever you are using it for). I figured I was probably going to buy just one of these TDS meters in my life, so why not just get the best and keep it for life. I can also just change the electrodes in the future if it needs it but from reading the instructions, I probably won't ever have to unless I start a hydroponic farm! The other thing I like about it is that it is waterproof - it feels strange enough dipping something with an electronic display into a solution so not worrying about whether it will be damaged or not and “how far am I dipping it in?” is a real bonus. If you need to monitor EC or TDS of solutions on a regular basis, then this is highly recommended - make sure you have a source of purified (reverse osmosis or de-ionised) water to wash the tip between uses and before storage to make sure that it does indeed last a life time!

I wasted a lot of money on cheap rubbish units before finding the HM Digital COM-100. This unit seems well made, the buttons are easy to use (although I'm not sure why they are offset to the right) and the screen is large and easy to read. I check the calibration with EC calibration fluid regularly and find the meter to be accurate to plus or minus three percent. This accuracy is fine for mixing up plant nutrients and I've not come across anything more accurate for this price

The meter arrived in good time and in good condition. I bought this meter to check water quality of a well. As a simple test, I compared the reading to that stated on a bottle of well-known mineral water and was gratified to see that the values correlated well. This was based on factory calibration - I didn't calibrate the meter myself. I am happy with the physical properties of the meter, it is sturdy, waterproof and has worked as described in the supporting literature. I would suggest that you read around the web as to the exact meaning/implications of the readings the meter gives in the context of your own requirements, I found the information I encountered most informative and useful...

If, like me, you have been scrolling and scrolling and scrolling through pages of Chinese rubbish, looking for a decent product that is going to last years and offer accurate results then I cannot recommend this product enough. It is well built, ironically, waterproof considering it is testing water… Yes, 95% of the others don’t! it is brilliant and very accurate and I highly recommend it.

When tested in 342 showed 567ppm calibrated now perfect showing 341ppm as close as it will get

Well build. Accurate, repeatable measurements with accurate indication of temperature. Waterproof. Mode ppm with conversion factor NaCl works best for me. (1 ppm = 1mg/L so 5000ppm = 5 grams / liter) Mains water at my home measures 204 ppm and my favorite bottled water (suitable for babies) 23 ppm.

One decimal place higher accuracy than my cheaper original one.Sems well made & sturdy. Backlight is useful when checking ppm on pure water tank in dark.

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

Great meter. Near instant readings, accurate, easy to calibrate and best of all, waterproof. I’ve accidentally dropped the whole meter into water, completely submerged for a few seconds with no problems.

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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 <20 ppm. I can also tell when the RO filters need changed out by watching the ppm count slowly rise over time. Frankly, this little TDS meter has proven to be very valuable for allowing me to monitor and control the quality of water and colloidal silver I use. I highly recommend it to anyone looking to purchase such an instrument.. For me, it works GREAT... Update: 1 Feb 2014 I 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...

Defekt nach 1,5 Jahren.