Help setting up OMRON PID Controller

Hi
I'm a complete newbie to control systems.
I just got an OMRON temperature controller, model number E5CS-R1KJX.
The manual which comes with it is not much use to me

I want to use this unit to control fermentation temperatures for my home brewery. This involves switching on a cooling source if too hot, and switching on a heating source if too cold to keep a stable temperature.
I have a couple of questions about setting up the controller.
I'm not sure if i need to use on/off mode or PID - I don't know what PID actually is. Can somebody explain?
The unit provides two relay outputs one for control and the other for alarm. I assume I need to provide my own relay contact protection/suppression?
Also, I accidentally bought the wrong model. I wanted the RTD model but got the thermocouple model - eBay one off, so no chance to change it. I know nothing about thermocouples. It looks like type K's are easy for me to get, but I read something about "compensating conductors" - what's this all about?
Regards, Mark
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proclaimed to the world:

PID is a type of control action. It is best for maintaining an accurate setpoint. On/Off has a range defined by the temperature at which the output comes on to heat and the temperature where it goes off. The amount of the band has to be big enough to not damage or wear out the devices that are used to heat and cool.

You need to provide a power connection that is breaker protected and has an on/off switch.

A thermocouple is two wired made of different metals connected to each other. There is a small voltage produced that is proportional to the difference between the temperature at the tip where the two wires are connected and the open end. You must use thermocouple wire all the way to the controller so that you can measure the temperature at that end. Simple.
What is not simple is going through all the programming that you must do by the keyboard to get this set up right. I would also have to know things like what you are using to heat and cool with.
Omeron's manuals are not easy for someone inexperienced to use. It would take a good amount of time for me to walk you through the process. Time that many of us here charge for IRL.
Be well,
HoP
The preceding message represents personal opinions and/or advice that may prove incorrect or harmful. But then maybe not. Feel free to disregard.
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I wouldn't have thought that fermentation required the accuracy of a PID temperature controller. PID systems use negative feedback of an error signal (difference between actual and desired temperature) which is then amplified proportionally (P), and/or integral (I) and/or differential (D) in varying amounts to compensate for thermal lag etc. A correctly tuned system will maintain a temperature within very fine limits, say + or- 0.1 Degs C.
A normal bimetallic thermostat should serve your purpose quite well, controlling a heated blanket or tray in contact with the fermentation vessel, or maintain the air in the fermentation room at the desired temperature with suitable fans to ensure mixing.
I you want to use the thermocouple PID system, thermocouple extension cable should be used, available from suppliers such as RS Components.
http://rswww.com/cgi-bin/bv/rswww/subRangeAction.do?cacheID=uknetscape
JPG
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Thanks for coming back to me about this.
Perhaps I don't need PID. I can't see any way of feeding back any error to the unit.
The main control is to turn on a flash chiller. This is a small refrigeration unit with a built-in recirculating pump, and is used normally under the bar to chill beer as it is dispensed.
I have a copper heat exchanger in my fermenter, and fluid gets pumped through this and via the chiller and recirculated to bring the temperature down - it's quite a common technique in brewing circles I'm lead to believe.
Regards, Mark
For heating (I assume I run this from the alarm? 1A *should* be ok IIRC) I'm going to use a standard 10g heating belt from a home brewing shop.
So if I want say to keep fermentation down to about 18C, what should I set the uppper and lower limits to? 17C and 19C?
Regards, Mark
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MarkMc wrote:

You don't send an error back to the controller. You tell the controller what temperature you want (called the "command" and give it a way to measure the actual temperature. The difference is the error. Error is determined and used internally by the controller and used in its control algorithm. Unless the error gets too large, it's not your concern.

That kind of on-off operation will be difficult to stabilize. It would be better to use a variable-speed motor so the controller can adjust the rate of cooling.

Find out from other brewers how they control it. Ignore any advice you get here.

The alarm is another on-off device. On-off controls necessarily produce limit cycles. it is the designer's task to make the cycle's amplitude small enough. If You're going to use on/off for the pump anyway, do that with the on/off alarm and use the proportional control for heat.

That depends on how small you can keep the limit cycle. Upper and lower limits are not the same as upper and lower boundaries of the proportional band. If you do no proportional control at all, you don't need a proportional band (or a PID controller).
Jerry
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Here's a link to the OMRON controller I have;
http://www.europe.omron.com/UK_en/cor/iab/home/product_catalog/Temperature_Controllers/General_Purpose_Controllers/auto_E5CS_series.asp
There are several models in the range, depending on whether it is RTD or thermocouple, relay contact or 12v output.
Mine is the model E5CS-R1KJX (thermocouple and relay contacts for outputs) and has on/off or PID
Regards, Mark
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MarkMc wrote:

If you use alarm contacts to do full heat, full cool decisions, without benefit if the PID algorithm, he limitation on how close you can put the two decisions is the overshoot you get after you turn off the heating or cooling process.
If the fully hot blanket continues to heat the liquid enough to raise its temperature 2 degrees, after the heat is turned off, then you set up will trigger the cooler, each time the heat turns off. If the cooler also has at least a 2 degree overshoot, it will do the same thing for the heater, and you will have endless echoes. So some experimentation is in order.
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JPG wrote:
...

It may be overkill for beer, but pharmaceutical fermenters require tight control for consistency. Typically, RTDs are used. It may be possible to maintain +/- .1C with a thermocouple, but in practice it isn't possible to know +/- .1C of what without frequent recalibration against a standard and conversion cures updated to that. My most challenging high-temperature system was a set of six liquid-phase epitaxy diffusion furnaces operating at varying temperatures just short of 2000C that would produce the same product from a given recipe. An error of .5C made the product worthless. I was able to provide that all furnaces ran the same temperature profiles, but the actual temperature wasn't known.

I'm sure a professional brewer could make do with that, but beginners need the best tools. A bimetallic thermostat should have adjustable hysteresis and needs a variable anticipator. (Home thermostats have variable anticipators and work poorly when those are not properly set. Computerized house thermostats do anticipation electronically and adjust themselves. They work with less overshoot after a few hours of operation.) I might not have chosen that particular controller (in fact, I would probably have built my own), but having it, I would use it.

Many thermocouples are a few feet long. If the controller is close to the fermenter, you may not need an extension. You do need a matching plug or an appropriate terminal block (This already on the controller, come to think of it). You need a good electronic cold junction. (You can make one of those, but it too may be built into the controller.) All in all, I would use an RTD at those temperatures if the controller supports it. You can use any wire with a 4-wire connection and no cold junction is needed. (There are 3-wire RTDs too.)
This gave me an error page. What was it intended to show?

Had you asked what to get, you might have been given different advice. Given that you have what you do, you need information on how to use it. One tip that many don't realize has to do with sensor placement relative to the heat source and the controlled material. It doesn't apply to stirred liquids, but you may eventually use your controller for another purpose (enameling furnace?), and you probably won't stir. In many systems, there is a time lag between the heater's changing temperature and the load's response to it. The obvious way to stabilize such a system is differentiation; that's classic. In many thermally regulated systems, by the time the load responds at all an excessive amount of heat may already have been pumped in. Especially when there is insulation surrounding the regulated chamber, the response to a step input can be more like the output of a delay line than a simple exponential rise. Placing the thermocouple in an appropriate place between the heater and the load provides some D term with no electronic help and often with increased stability. A little D more from the electronics is usually best.
Systems that don't need to respond quickly to step commands work well with very little integrator gain. The integrator will settle on the right level eventually, and that's all that matters. Is such a case, it comes clear why the integrator gain is called "Reset". That literally means "set again", i.e., change the setpoint. That's all the integrator needs to do.
Jerry
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MarkMc wrote:

the internet can
there are simple tuning guides for heater loops out there that will give you a good result
without reading the book on your controller...usually PID loops have an analogue output fed to an analogue contactor...presumably this is built in to the unit
cooling?...not likely...power input to the heaters will reduce as process value reaches the set point to maintain a stable temperature
or wildly unstable
tuning the controller to the process is the art of it
find the autotune button and use it!
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