I Bought a second hand STC-1000 unit a few months back and it did not come with a probe. I could not locate a probe that I could buy and have shipped to my location so with some searching on here and other sites I found the specs for the probe and decided to try building my own. I confirmed yesterday that it works so for your references here are my notes.
The STC-1000 supposedly uses a NTC-MF52AT 10K +-5% 3470 thermistor resistor. Looking at the resistance value chart for this and other resistors I found that the NTC-MF52AT 10K +-5% 3950 looks like it has the same resistance values at different temperatures and should (does) work as well.
Here is a link to an ebay seller for reference of what the resistance chart looks like - I am not endorsing any particular seller.
10k OHM NTC Thermistor Resistor NTC-MF52AT 10K +-5% 3950 +-1%
The thermistors I purchased are 2mm wide and will fit in pretty much any sized tubing you want to use for housing them. - the tighter the fit the better the readings will be of course.
- A friend advised using shielded cable for the sensor wire, however I just used some random wire I had laying around and it worked fine (I used only 1 meter, longer sensor cables probably would benefit from the shielding to reduce noise)
- I just used regular solder to connect the wire to the leads on the thermistor.
- The thermistor was very cheaply purchased from China; about 500 yen (5 bucks) for 2 packs of 10. The same seller is using Aliexpress and Ebay, however there are many sellers for these parts. I chose my seller because they displayed more details and had free shipping internationally (which took 3 weeks to arrive). No customs fees incurred while shipping from China to me in Japan.
So now I have a temp probe for my STC-1000 that works well, for about 30 cents per probe without any housing. It is up to you to figure out housing or waterproofing your own. I will make probes for several pieces of equipment that will be permanently mounted, and just switch out the leads to the controller unit when I need to.
I have no idea how long the probe will last, so if anyone does this and has problems please post!