FlashTrax
Harmless
Posts: 6
Registered: 7-10-2021
Member Is Offline
|
|
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.
|
|
|
WGTR
National Hazard
Posts: 971
Registered: 29-9-2013
Location: Online
Member Is Offline
Mood: Outline
|
|
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).
|
|
|
FlashTrax
Harmless
Posts: 6
Registered: 7-10-2021
Member Is Offline
|
|
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]
|
|
|
WGTR
National Hazard
Posts: 971
Registered: 29-9-2013
Location: Online
Member Is Offline
Mood: Outline
|
|
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.
|
|
|
monolithic
Hazard to Others
Posts: 436
Registered: 5-3-2018
Member Is Offline
Mood: No Mood
|
|
160 C seems too low. Nurdrage uses a similar hot plate in his videos, it has no problem hitting 200 C.
|
|
|
Texium
Administrator
Posts: 4580
Registered: 11-1-2014
Location: Salt Lake City
Member Is Offline
Mood: PhD candidate!
|
|
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.
|
|
|
FlashTrax
Harmless
Posts: 6
Registered: 7-10-2021
Member Is Offline
|
|
okay guyz wonderful answers now I know I can keep my hotplate and start using it...
|
|
|
Rainwater
National Hazard
Posts: 919
Registered: 22-12-2021
Member Is Offline
Mood: indisposition to activity
|
|
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
"You can't do that" - challenge accepted
|
|
|
FlashTrax
Harmless
Posts: 6
Registered: 7-10-2021
Member Is Offline
|
|
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
|
|
|
Fantasma4500
International Hazard
Posts: 1681
Registered: 12-12-2012
Location: Dysrope (aka europe)
Member Is Offline
Mood: dangerously practical
|
|
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.
|
|
|
Tsjerk
International Hazard
Posts: 3032
Registered: 20-4-2005
Location: Netherlands
Member Is Offline
Mood: Mood
|
|
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.
|
|
|
FlashTrax
Harmless
Posts: 6
Registered: 7-10-2021
Member Is Offline
|
|
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?
|
|
|
monolithic
Hazard to Others
Posts: 436
Registered: 5-3-2018
Member Is Offline
Mood: No Mood
|
|
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
|
|
|
FlashTrax
Harmless
Posts: 6
Registered: 7-10-2021
Member Is Offline
|
|
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!?
|
|
|
Rainwater
National Hazard
Posts: 919
Registered: 22-12-2021
Member Is Offline
Mood: indisposition to activity
|
|
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 #.
"You can't do that" - challenge accepted
|
|
|
macckone
Dispenser of practical lab wisdom
Posts: 2168
Registered: 1-3-2013
Location: Over a mile high
Member Is Offline
Mood: Electrical
|
|
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.
|
|
|
Rainwater
National Hazard
Posts: 919
Registered: 22-12-2021
Member Is Offline
Mood: indisposition to activity
|
|
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]
"You can't do that" - challenge accepted
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
