Must all pH sensors be long, magic marker sized probes?

I'm working on a new project for fun at the moment. It's a little robot that wanders around collecting envinromental data and one particularly useful bit would be a pH reading of water. Judging from what I've seen these probes all have a very similar form factor roughly the size and shape of a magic marker. I'm not sure if this is partly due to their intended use by human operators or for some techincal reason but so far I haven't had much luck finding a miniaturized pH sensor that I could cram onto this little guy. I did find this one ebay example, not sure just how much I'd have to add to get a useful signal into a microcontroller but we're getting into the ballpark now. I also saw this article from 2016 but I haven't found a "for sale" option for a component like that. Also, they seem like a bit of a hassle with all the calibration and maintence- maybe not worth the effort but I'd be delighted to hear some ideas from anyone familiar.

BTW- as this is a technology demonstrator cost is a factor and accuracy isn't (particularly).

How small do you need the sensor? I can see the one you link to is a10mm long 5mm diameter tip.

I have seen this one, much lower cost but much larger, for example: Mini Lab Grade pH Probe – Whitebox Labs (whiteboxes.ch)

Or for something more ambitious Microsens SA - pH-ISFET sensor (No price that I could see so probable £££££)

Having lots of fun is how I make my living.

Well - what is it that you are doing to earn money?

Oh, hi Stefan!
I'm an inventor- rarely do I venture into programming tasks but now that I've started to enjoy it I expect that to change. Forturnately the fun projects lead to more motivation. This particular one is especially neat but not for profit. If you'd like to see some inventions I'd be glad to share but I figured you want to stay on topic.

Haha, yea that 2nd example is more what I was expecting to find, but I agree with you- likely big bucks. That said, i've since noticed a similar example here and there usually from a university or research organization but I'm surprised these evidently aren't readily available for sale, only the usual designs with a surprisingly similar form factor. Your 1st example is pretty close size-wise, but I'd probably try to crack the subassembly out of the enclosure and lose the cable. Thanks for the post!

No I'm really interested in it. Write about some inventions you have made. If you think it is too offtopic just send a private message
best regards Stefan

Well, I also have a curious 4yr old girl whom I've been taking time off to build & experiment with- she's probably better at coding than I am at this point but she also benefits from this forum. I created a website in recent years as a motivator to dump all this media I've been collecting somewhere, its kind of just turned into a private website with fun stuff but still lots of inventions. That site is www.nothingnormal.net if you're interested. The arduino examples include the stranger things lights, Falcor (costume) eyeballs, and sea monkey aereator (which I don't think is posted yet). For profit is a licensed nail trimmer I called "LumaTrim" but was released as "PetiCare" that you can buy at Walmart, BB&B, and Petco (the 1st patent I actually own). Also available (and duplicated by more than a dozen china knockoffs) on amazon. Here's the one genuine link.

A 2nd cleaning item (also my 2nd owned patent) will hopefully come out this year with Popular Mechanics branding (fingers crossed!).

I used to work at Enventys/Everyday Edisons and worked on lots of inventions as part of their TV show, one of the most popular (still selling) being the gyrobowl- an evolution of a concept that Brad & Melinda brought to us.

The project this post is about has a bit of a national geographic affiliation but isn't for commercialization- kind of trying to pivot my career toward some more sciencey goals and this is one of the first steps for practice & fun. I can send you a PM with a video demo if you want.