Heater used in my application

Following is the heater I am using in my application.



I am not getting, what is the type of this heater, so that I can order this part.

It has two pin.. so I want to know how to control heating mechanism? Please someone explain. This application is new to me and I have little knowledge about this.

Thanks in advance.

What is its rating? where is it used? What is your application?
Frank

It is used in biochemistry analyzer where its used to heat sample (liquid) and required temp is 37 C. I don't know the rating and type of this heater. I need to order it so need details about it.

What makes you think it is available to you?

It's operating at 18.5 volts. I don't know about heater and need to have details for my project. So please guide.

It's apparently a custom made heater and most likely not available from stock. It may be listed as a spare part from the instrument manufacturer.

It looks like a typical "glue on" foil heater on a silicon rubber/glass texture carrier. Probably low power. You can easily get it's rating by measuring the resistance, presumed it's not a self regulating PTC heater (unlikely).

How large is your liquid sample? To heat a test tube with 1...10 ml of a liquid to 37 deg.C, a hand is enough. So you need say one-watt heater, possibly a set of 1W resistors arranged around the sample.

Its resistance is 35 ohm, Its one end is connected to 18.5 v and other is connected to Drain of MOSFET and gate of the same MOSFET is driven by I/O pin of controller.

I want to know power rating of heater and want to design power supply for it.

What voltage should I need for such heater?

From Voltage =18.5 v and R=35 ohm, I is 0.528 Amp and hence power will be aprox 10 Watt.

Is this calculation correct? If I want to order it for my application, what will be ideal and practical rating?

Thanks in advance.

vaibhavpawar said:

Its resistance is 35 ohm, Its one end is connected to 18.5 v and other is connected to Drain of MOSFET and gate of the same MOSFET is driven by I/O pin of controller.

I want to know power rating of heater and want to design power supply for it.

What voltage should I need for such heater?

From Voltage =18.5 v and R=35 ohm, I is 0.528 Amp and hence power will be aprox 10 Watt.

Is this calculation correct? If I want to order it for my application, what will be ideal and practical rating?

Thanks in advance.

Click to expand...

Your estimate is correct. To control the temperature of a small volume to ~37 deg.C, you need some metal enclosure insulated from the surrounding objects (by a PS foam or similar), with a heater wire around it and a thermistor in it. I used a simple comparator like LM 311 to trigger MOSFET gate on or off to keep the temperature stable. If you need a finer regulation, use a 555 as a PWM generator.
You can find a lot of simple circuits or design yours.

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If the specifications are as you wrote,you need a 18.5V, o.5A DC power supply. As in fact you need less than 5 W of input power you can use a smaller voltage if the controller circuit can work with it. Use a wall plug-in 12 VDC or 15 VDC regulated power supply.
To calibrate, put a J/K thermistor in a test tube with water and insert in the regulated holder. Follow the temperature and adjust it to 37 deg.C or where you need it. Depending on volume such adjustment may take up to 2 hours.

Many years ago, instead of such complex electronics there were adjustable-contact thermometers that worked well to < 0.1 deg.C using only one relay in the "power" circuit.

jiripolivka said:

Many years ago, instead of such complex electronics there were adjustable-contact thermometers that worked well to < 0.1 deg.C using only one relay in the "power" circuit.

Click to expand...

An aquarium heater cycles over a wider range of temperature, although it doesn't sound too different from this. I used one in my aquarium.

I would suggest it for the OP but I'm not sure they go up to 37 deg C.

You can use Nichrome ribbon wire ( Like in a toaster) and wrap 50 turns to get 10 to 20 Watts coated with PU or epoxy and two thermistors to regulate temperature. Insulate to regulate heat loss. A thin container that conducts heat well is required.

We used a similar method to heat crystals with SMT on flex board in foam to measure offset at 40'C and 70'C