Greetings fellow nerds.
In this video we’re going to make a thermometer for this hotplate.
Recently I purchased this hotplate stirrer from a company called Westlab here in Canada.
You’ve seen me use this so far in a few of my latest videos.
For the most part the hotplate stirrer works fine and reliably.
Although the ceramic coating on the heating element is rather easy to chip.
What really pisses me off about my purchase though is that the website implies it has a thermometer probe but i never received one.
When i emailed the seller about this they never responded.
The hotplate clearly has the required port for a thermometer probe, but that’s no good if the probe isn’t provided.
The website doesn’t even list the probe for sale. At this point I decided to go to the original manufacturer.
First place to look for them is the operating manual.
I was no better off as it seems like the manual was not written by a person who speaks english as their primary language so the manufacturer was likely foreign.
But the worst part was that the manual did not specify any manufacturer anywhere.
Almost all equipment has the manufacturer listed somewhere but this one doesn’t.
It has model numbers but without stating which manufacturer uses them those numbers are worthless.
I’m starting to think i bought some sort of imitation knockoff.
The only clue I had was the logo here ISG.
Looking online the closest thing i could find was international scienfific group. At least the logo matches.
But half the website doesn’t work and the other half looks like it hasn’t been updated since 2011.
The contact information listed for canada is actually Westlab where i bought the hotplate from.
Since i already got ignored by them it looks like i reached a dead end.
But since the operating manual makes me think it’s a knockoff maybe i can find a similar product with the same design and specifications.
Continuing my research i was eventually lead to a company called scilogex that sells an almost identical hotplate with just the logo being different.
Finally i had a way of obtaining the thermometer probe even if i had to buy it from a different company.
Now the price wasn’t listed so i checked into ebay as the prices usually follow the market. And here it is.
Around 161 american dollars.
F--- THAT.
I’m not paying an extra 161 american dollars for a F---ing piece of vapor deposited platinum on ceramic.
I will f---ing make one. Ya think i got a Ph.D. in chemistry just to bend over and take it the a-- on lab equipment? Little f---ers.
Okay, okay, sorry for that outburst... Okay.
So how do we go about making our own thermometer probe? Well we first need to know what type of element it uses.
A big hint is right in the manual, it calls it a PT1000 sensor element.
Now this might just be a coincidence, but PT1000 could mean it uses a platinum resistance element with a resistance of 1000 ohms at zero celsius.
To be certain I’m going to test it by sticking this 1000 ohm resistor into the thermometer probe port.
This will simulate the connection of PT1000 element as the circuitry can’t tell the difference.
Oh yeah before doing any sort of electrical testing unplug the equipment.
Sticking things into a live socket is usually a bad idea.
Now there are five holes so there are ten ways to stick in a two pin component.
Fifteen if you include the outer grounding sheath.
I’ll just have to try them all and hope i eventually hit on the right one.
First i’m going to try the two rightmost pins.
Okay i’m going to put the plug back in and check it out. Well what do you know, i got lucky and it’s working.
The hotplate registers the probe is connected by showing this display. And it’s reading the temperature as one degree celsius.
This is consistent with resistance of a PT1000 element since our fake resistor at 1000 ohms should register zero celsius.
To be certain i’m going to connect another 1000 ohm resistor in series to get us 2000 ohms.
Now for those of you wondering, the serial port in the middle of the hotplate is for reading off the temperature with a computer.
Useful for automated lab equipment and experiments.
Personally i don’t need such a feature but who knows what will happen in the future.
Anyway, back to the resistors.
A standardized PT1000 sensor registering 2000 ohms means it’s at a temperature of around 259 degrees Celsius.
And that's what it sees it at.
We’re a bit off but i’ll attribute this to the resistors not being perfectly 1000 ohms each.
This is still nonetheless consistent with the response of an actual PT1000 sensor element.
Now that we know this works, we can get our parts and build a proper PT1000 thermometer and reasonably expect it to work.
The first thing to buy is the sensor element. I got this PT1000 cartridge type element off ebay for about ten dollars.
You can also buy the bare element by itself but I wanted the cartridge for more durability.
Now you can try inserting the leads into the connector but that’s pretty unstable and wires are too short to be useful.
So let’s get ourselves a proper connector. It looks like this is a standard DIN-5 connector. Let me see if i can go find one.
It just so happens I kept my old keyboard from one of my computers from 20 years ago. Keyboards this old used DIN-5 connectors.
Wow, twenty years ago… all of a sudden i feel really old and have the overwhelming urge to sit in a rocking chair on my front porch and yell at kids to get off my lawn.
Anyway, let’s first check if this connector really does fit. Looks like it works.
So this keyboard will finally have some use twenty years later as an organ donor for my thermometer probe.
Now we just cut the cord.
And we have our connector and cord ready. Using a pair of scissors we strip off the outer sheath.
And now using an ohmmeter we determine which of these wires correspond to the two leftmost pins of the connector.
Remember that since this is the male side of the connector the pins are flipped so what was on the right is now on the left.
Looks like the grey and yellow wires are the wires we want.
We now strip off the insulation of those wires. And then we solder the wires to the two leads from the sensor element.
At this point I must admit that i’m just a Ph.D. chemist and not a much higher paid and skilled electrical engineer.
You actual electrical engineers are probably laughing your asses off at my soldering technique.
Anyway, once we’re done soldering. We insulate the leads from each other with some tape.
We’re almost done. Here is the sensor with the cord and connector attached.
While we could use it as is the cartridge would be destroyed by acid pretty quickly so we’ll use this pipette to protect it and create a glass encapsulated thermometer probe.
First we close one end using a torch.
Make sure the seal is complete and leak free before letting it cool.
Now while we can use it like this there is still the danger that i might drop the probe too far and chemicals can still get in.
So I’m going to use a 1/4" vinyl tube to connect the glass tube as well as to sheath and protect the wires.
You can also use a much longer glass tube if you happen to have one.
Although i still recommend using some vinyl tubing at the top so you can seal the cord.
I’m not worried about melting the plastic as i only intend to use this for temperatures below that.
But if you intend to use the full range then you’ll definitely have to obtain a longer glass tube.
Be sure to thread the cartridge all the way to the bottom. Now we seal the cord with some iron wire. You can also use a hose clamp.
With enough twisting we can clamp down on the tubing and seal it against the cord.
Now there is no way for chemicals to get in and corrode the connections.
And there we have it.
It is connected to the hotplate stirrer and correctly measuring the temperature of the room.
Now we put it some ice water. Looks like the circuitry can’t measure any temperature below 1 degree celsius.
But this is a fault of the circuitry and not the probe.
Here i am using the temperature control function of the hotplate to maintain the water at a constant 95 degrees Celsius.
It looks like we were successful. For about twenty dollars worth of parts we made a thermometer probe and avoided paying a f---ing s---load for the actual one.
Thanks for watching.
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