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Author: Subject: Condition of a used hotplate
FlashTrax
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[*] posted on 19-1-2022 at 12:12
Condition of a used hotplate


Hello, I've bought a IKA RCT basic (manual knobs) for aroud 200$

This is the test with mineral oil and a thermometer able to reach 300°c

his is the results (first the setting of the hotplate and after the reading of our digital thermometer who can handle temp range until 300°c.

300°c >>> 160°c
200°c >>> 120°c
100°c >>> 55°c
(first is the setting of the heat on the hotplate knob and second the reading on thermometer)

We can establish that we never reach the right target. We estimate a loss of 50% accuracy with this device that is sent as Good Condition.

The vendor offering me a replacement but do you think it's worth to pay for the cost of return the item and waiting... I mean maybe all used hotplate stirrer is like this?
Thanks for the ideas.
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WGTR
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[*] posted on 19-1-2022 at 12:37


Do you have a temperature probe in the oil bath that is plugged into the hot plate? This is unclear from your post. If not, then this temperature reading is for the hot place surface and not for whatever is sitting on top of it.

If the answer is "yes" then try the test again with the temperature probe unplugged and see if your results are different. If not, then something is broken (maybe the probe, hotplate electronics, etc).




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FlashTrax
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[*] posted on 19-1-2022 at 12:51


I use a good digital thermometer that can reach 300°c. I put a 250ml Erlenmeyer on the plate. It is filled with 200ml of mineral oil and the digital thermometer is bathed in it (no probe avaible).

[Edited on 19-1-2022 by FlashTrax]
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WGTR
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[*] posted on 19-1-2022 at 13:03


If no probe is plugged into the hotplate, then it is quite normal for the temperature of an oil bath (for example) to be much cooler than the reading on the hotplate itself. The error depends on the size and shape of the beaker, how much air is flowing past it, and other unknown variables. An error of 50% sounds about right in general.



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monolithic
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[*] posted on 19-1-2022 at 17:01


160 C seems too low. Nurdrage uses a similar hot plate in his videos, it has no problem hitting 200 C.
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[*] posted on 19-1-2022 at 19:47


I agree with WGTR. Were you stirring the oil or not? If you weren't stirring it, it's even more likely that it is not heating evenly and the heat from the surface of the plate will not be distributed throughout the entire volume of oil. 200 mL in a 250 mL flask means that a significant portion of that oil is pretty far from the heat source, and may be cooling down faster than it can be heated.



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FlashTrax
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[*] posted on 21-1-2022 at 07:55


okay guyz wonderful answers now I know I can keep my hotplate and start using it...
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[*] posted on 22-1-2022 at 01:53


Try placing the temp probe directly on the hotplate with a piece of insulation over it.
With no probe plugged into the hotplate, it can only see the temp of the plate itself




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FlashTrax
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[*] posted on 29-1-2022 at 00:59


the vendor of me to replace this item with another IKA RET which have the "safety control" so Im waiting to get it and will make new tests as stated here and will be back with updates
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[*] posted on 5-3-2022 at 04:33


crank open the device, near the knob you will find a mechanism that triggers when you turn the knob. you will look for a small piece of metal that moves when you turn the heat up
then with a piece of pliers carefully pry this thing so that its more open
the mechanism is that when it heats up this metal piece causes something to contact and the device turns off
i successfully did this yesterday with a cheap hotplate, only downside is that it desires about 35*C as soon as i plug it in and its at 0
i couldnt get it really warm but now it goes to at least 600*C and the knob still does work, the temperature range just moved a lot higher up
put some insulation inside the device and create an aluminium oxide insulation cup and youre set for small scale aluminium casting.




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[*] posted on 5-3-2022 at 06:37


You shouldn't be doing what Antiswat is proposing to a functional IKA. They are designed to work with a thermoprobe, but with a small shortcut in the probe connector they function (mine does) measuring the temperature of the heating plate itself.

When you insulate the plate with aluminum foil, the temperature of what is on top of it gets close to the set temperature. Without insulation obviously the temperature of what is on top will be lower, depending on the contact between the beaker/flask and the plate.
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[*] posted on 26-3-2022 at 05:54


my project is progressing but:

my IKA RET Basic does not have a thermocouple sensor probe.
It seems to me that it is one of the first models and I have no idea which exact probe I should connect.

It is a DIN 12 878 socket and I just know that I need to connect wires 3 and 5.

But I have no idea what type of probe: K, E, J, ...?
PT100 or PT1000?

The manual is very imprecise it just say that it is a contact thermometer with or without safety. They want me to buy their expensive original ETS-D but I want the NurdRage method of DIY. Just need to connect wires 3 and 5 is okay for me.

How do I know what kind of probe I need?
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[*] posted on 26-3-2022 at 11:38


Quote: Originally posted by FlashTrax  
my project is progressing but:

my IKA RET Basic does not have a thermocouple sensor probe.
It seems to me that it is one of the first models and I have no idea which exact probe I should connect.

It is a DIN 12 878 socket and I just know that I need to connect wires 3 and 5.

But I have no idea what type of probe: K, E, J, ...?
PT100 or PT1000?

The manual is very imprecise it just say that it is a contact thermometer with or without safety. They want me to buy their expensive original ETS-D but I want the NurdRage method of DIY. Just need to connect wires 3 and 5 is okay for me.

How do I know what kind of probe I need?


This link claims PT1000. http://staff.washington.edu/wbeaty/chem_stir.html
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[*] posted on 26-3-2022 at 15:45


thanks but my plate is really not this generation. I don't own a digital one.
My plate is old with analog selectors for stirring and heating.

Im not sure they use the same accesoires since 10 years bro!?
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[*] posted on 26-3-2022 at 17:14


If you know the correct pins. And are sure of the pins.
Place a volt meter across them. Should read whatever logic voltage the adc uses. 1.3/3.3/5 are standards.
If you see this, then it's either a pt100 or pt1000
Place a potentiometer or other resister across them..

If 100 ohms reads 0c, then you need a pt 100
If 1000 ohms reads 0c, then you need a pt 1000.

If you can not read a voltage than it could require a thermocouple or be damaged.
Crack that baby open and follow the 2 pins to an ic chip and google the #.




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[*] posted on 27-3-2022 at 23:42


I am pretty sure the older ones used a pt-1000 probe as well.

Their probes are digital thermometers no clue how they work.
Probably one pin is power, one pin is ground.
Not sure if the probe does the on-off or the plate itself.

When a probe isn't connected it uses an internal surface sensor.
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Rainwater
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[*] posted on 3-4-2022 at 03:44


Is this your hotplate?
https://www.ika.com/en/Products-Lab-Eq/Magnetic-Stirrers-Hot...

If so this is the part you want to make
https://www.ika.com/en/Products-Lab-Eq/Vacuum-csp-158/PT-100...

Here is one already made. You may have to adjust which pins are connected to match your hotplate
https://www.amazon.com/FOUR-ES-SCIENTIFIC-External-Temperatu...


https://youtu.be/ORBgemwMLS4
Here is a video showing the basic procedure.

be sure to double check the connectors before you buy anything I suggest

[Edited on 3-4-2022 by Rainwater]




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