Temperature Controller- connecting output with a particular heater

Thread Starter

arindam456

Joined May 27, 2024
4
I have one temperature controller (https://www.selec.com/product-details/universal-pid-with-white-green-display). I want to control the temperature of a stainless steel block using a cartridge heater with 50-ohm resistance and a tolerance of 50V.

I am new to instrumentation. I can't figure out how to connect this temperature controller's output to the heater. I feel I have to use an external power supply for this. However, I don't know how to decide which power supply I should purchase.

Secondly, I would like to use the analog output to control the heater. I think that will provide me with better stability. However, I am open to using the SSR output to control the heater.

Mod: added datasheet.


You can find the details of the temperature controller in the attached links.
Thank you in advance.
 

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Ian0

Joined Aug 7, 2020
10,277
I want to control the temperature of a stainless steel block using a cartridge heater with 50-ohm resistance and a tolerance of 50V.
Do you mean that you heater is rated for a 50V supply?
In which case you need a 50V transformer (NOT a 50V power supply), because the outputs are rated for up to 250V AC but only up to 28V DC
 

Irving

Joined Jan 30, 2016
4,070
Assuming something like this:
1716808322536.png

its going to take 1A. I'd use a MOSFET switch on either the SSR output or the 10v DC output with a 48v 75W switching supply. An IRFZ44n or similar will handle the 1A without a heatsink and a SMPS will be a lot cheaper than a 50v 50VA transformer.
 

MisterBill2

Joined Jan 23, 2018
19,466
No question as to what to use. It should be a SSR made by a reputable company and stocked by reliable suppliers , and selected to have at least a 50% excess current rating and to be controlled by the controllers output .

There is no mention of the temperature intended nor the accuracy required, nor is there any mention of what will be used to sense the temperature. and those details do matter. If you need to hold the temperature within 0.01 degrees C that controller will not be adequate.

Now my serious question is just how would you use the analog output to control the heater??? That output is an instrumentation level signal, so any control of the heater will require an interface of some kind. NO WAY will an analog control be simple or cheap to make work properly.
The controller in the data sheet already has an on/off time proportional control output that can drive an SSR to switch the heater on and off, PWM style, at a one second update rate. You are not going to get much better than that. In addition, you can use one of the alarm contacts to switch the heater to a lower power mode when the temperature is closer to the target value.
 
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Thread Starter

arindam456

Joined May 27, 2024
4
Assuming something like this:
View attachment 323228

its going to take 1A. I'd use a MOSFET switch on either the SSR output or the 10v DC output with a 48v 75W switching supply. An IRFZ44n or similar will handle the 1A without a heatsink and a SMPS will be a lot cheaper than a 50v 50VA transformer.
Thank you for the suggestions. Can you please tell me about the electronic connection to use the MOSFET?
 

Thread Starter

arindam456

Joined May 27, 2024
4
No question as to what to use. It should be a SSR made by a reputable company and stocked by reliable suppliers , and selected to have at least a 50% excess current rating and to be controlled by the controllers output .

There is no mention of the temperature intended nor the accuracy required, nor is there any mention of what will be used to sense the temperature. and those details do matter. If you need to hold the temperature within 0.01 degrees C that controller will not be adequate.

Now my serious question is just how would you use the analog output to control the heater??? That output is an instrumentation level signal, so any control of the heater will require an interface of some kind. NO WAY will an analog control be simple or cheap to make work properly.
The controller in the data sheet already has an on/off time proportional control output that can drive an SSR to switch the heater on and off, PWM style, at a one second update rate. You are not going to get much better than that. In addition, you can use one of the alarm contacts to switch the heater to a lower power mode when the temperature is closer to the target value.
Thank you for your reply.

Our required highest temperature is 450 deg C and an accuracy of 0.2 deg C is good. We will use a Pt100 sensor for temperature sensing. What type of SSR or SSR specifications I should look for?
 

MisterBill2

Joined Jan 23, 2018
19,466
If the heater power is being switched directly, then the SSR must be rated to carry the heater rated current with an adequate margin, and also rated to be able to withstand the heater supply voltage in the OFF condition. The control voltage for the SSR must be suitable for the ON/OFF control voltage you will be using with the controller you have. Since you seem to already have the controller, that will probably be easy to discover. Common SSR control voltages are either 5 volts DC or else the 12 to 24 volts range. If the rest of the setup already has a voltage supply available that can spare the 10to20 milliamps to operate the SSR that would be an easy choice.
 
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