Milwaukee are solid ones. I prefer the ones with a separate probe.
And don't fall for the horror probe stories, spending +$60 on a yearly replacement..
I've been using a Milwaukee SMS122 for over 2,5 years now with this probe.
https://www.banggood.com/PH-Electro...ntrol-Meter-Sensor-p-912723.html?rmmds=search
Ordered 2 in case, still working with the same one all this time.. Works like a treat and didn't even need a refill..
Tho must note: The Milwaukee doesn't have a ground pin, well it must have but it'sbuild in and very low current, this makes it very susceptible to electrical interfearance... I had to place it inline away from any electrical source to eliminate any disturbance.. Because it's an SMS with a build in Relai, disturbane cause the relai to shake ratle and roll like mad..
The Hanna equiptment also is very high end, some come with a seperate Ground pin to eliminate this, can't be disturbed, but have a relative high working voltage and current between pin and probe for that, it's measurable in the tank water with a multimeter between 1,5 and 3 volts and even can feel the current flow in you ground yourself en stick a finger in the water. If you can feel a tickling sensation try to imagine what the fish feel swimming near it.. In the long term i doubt it is heathy for them, these high current grounded devices are not realy designed for aquarium use, this is in my opinion horticulture stuff only. Physicaly grounding an aquarium is a questionable practise anyway, any small electrical leak will start flowing affecting fish with sensation. So actualy using any type of permanent electronic measuring device in an aquarium it means the tank is permanently grounded to the electrical grid, simply because without any grund the device wont work. Than with using this type of device it is adviceabe to regularly check for power leakages with a multimeter between tank water and ground.. If the tank isn't grounded electricity can't flow and can't cause sensation. But again such a device grounds the water permanently than it becommes rather important. This is something you can't see with your eyes, nor maybe feel, but your fish might and not realy like it. It just shouldn't be there..