HM Digital HMDCOM100 Waterproof EC/TDS And Amp Temperature Combo Meter

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

Really good no problem until now

Its USA product , people don't buy it ... Customer care didn't take replaced b'z it did not work

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.

Works fine

Quick summary first and full review below:Positives:Rugged designWaterproof and dust proofBatteries and lanyard includedDifferent measurement optionsCalibration optionInstructions in clear EnglishGives quick, reliable readingsReplaceable sensor (although not readily/cheaply available in UK)Negatives:Screen not very large and not illuminatedInstructions in small printSlightly 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.

Very slow to stabilize.

If you're looking for a rock solid tds pen for shrimp keeping this is it. The temperature reading while testing tds is a nice feature. It gives quick and reliable readings right out of the box. Verified calibration once I received it with the hm digital calibration fluid and it was dead on.