1 – Get to know your own process
Do you already have something installed or are you going to install a new controller? If you want something new go straight to step 2. If you replace something existing make sure you check what is the controller connected to: What is the probe like? Is it a Thermocouple / Pt100 probe? Or does it deal with a 4-20mA signal? Then what output do you need? Just a relay switch? A signal for a SSR? A 4-20mA signal
2 – Decide what type of quality you want
Here is the good news: most controllers out there will do the job for a basic process. So the real question is: Do I take the cheapest item from China or do I trust a reputable manufacturer? The big difference is reliability (don’t expect a Chinese controller to last more than a few years) and accuracy. Cheap manufacturers make the specs look better than they actually are while reputable manufacturers coming from Japan or Germany for instance have a very strict quality system in place.
3 – Shop around and Check the Data Sheet
Get on different website, try to get a feeling of the way the controllers work, are they easy to use, do they have a large display…
Checking the specifications can be confusing so here are some tips: Almost all the controllers will accept Thermocouple, Pt100, Voltage/Current input and have a relay/ssr/current/voltage output option – the big difference is that you will have to order it with the right input type for some of them as this cannot be changed afterwards. If it says “universal input” then you should have the ability to change the input type to whatever you want. Check also the amount of relay alarm you want and if you need any fancy stuff like RS485 communication and/or possibility to connect to a computer etc…
4 – Get on the phone!
All of this to ask for help? Yes but at least you are well prepared to ask for a quotation in the best conditions. If you don’t go through the previous steps before calling an sales rep chances are that you are going to end up with the wrong item… or you are going to spend ages explaining what you are after!
5 – Don’t forget the accessories!
Do you need a temperature probe? Some extra cable? An SSR (solid state relay)? A transmitter? Make sure you don’t forget anything so that you can get on with the installation as soon as you receive your temperature controller…
There are many companies out there that can help – in the UK Coulton Instrumentation is known for the quality of their advice and the reliability of each
http://www.coulton.com/Temperature_Controllers_PXR_Fuji_Electric.html”>Temperature Controller they supply.