A rough calculation shows you can move the temperature of an ounce of water by 4 degrees F per second with 250 watts. I think you're using too much power for the heater because the time constant of the mass of the heater and container is more than 4 seconds. By the time you measure a temperature change, you have too much heat energy in the mass of the heater and container.

 

Rex c100 would putting these settings mean it would work the same?

If mechanically the same, yes.

What's the value of T that you are using?

 

If mechanically the same, yes.

What's the value of T that you are using?

If you mean temperature its 200c which gives me 185 c inside the cup.

 

No, the T parameter, which doesn't look like a "T" and has a value of 1 to 100 seconds. The symbol looks, sort of, like a flag.

 

No, the T parameter, which doesn't look like a "T" and has a value of 1 to 100 seconds. The symbol looks, sort of, like a flag.

Thanks for sticking with me I'm getting close.I thought that was an r so its a T it is set at 33.

 

Try lowering it to 16 and see if it gets better, then keep lowering using the 16, 8, 4 2, 1 sequence. I think the process will do better at 1, if I understand it. You may have to re-evaluate P, I and D.

The "setpoint" is what you want the value to be. In your case temperature.
The "measured value" is the current temperature or whatever.

These are standard industry terms.

 

The way I see 33 is that 10% on means 3.3 seconds and your thermal mass isn't that large and 250 Watts is too high. based on #12's calc's being on for 3 seconds will raise the temp more than 20 degrees at 10% power. That's a bunch.

Phase angle firing generally always works, but it's costly. I forget a lot of my Thermodynamics, but with the weights of the material and the material name, you can figure out how much heat you need to get it from one temperature to another in a given time. Those calc's escape me now.

 

Basic theory says you should have a heater that is near its maximum capacity when maintaining equilibrium conditions at the target temperature. Hosing a bee hive by means of convection is not a 30 second job. You don't need to inflict enough energy to sublimate the whole batch in under a minute. You need to slow it down enough that the temperature sensor isn't lagging behind the actual batch temperature by more than the allowable error.

 

Basic theory says you should have a heater that is near its maximum capacity when maintaining equilibrium conditions at the target temperature. Hosing a bee hive by means of convection is not a 30 second job. You don't need to inflict enough energy to sublimate the whole batch in under a minute. You need to slow it down enough that the temperature sensor isn't lagging behind the actual batch temperature by more than the allowable error.

I don't mind how long it takes to do the sublimation but what I do want is never go over the 200 its proving very tricky to stop this although I am getting very close.

 

Just a thought....

You should be able to operate the T-controlller as "sort of a variac" by shorting the thermocouple input with a wire. If the TC range includes ambient, then the temperature will be ambient. With I and D zero, you just have a proportional controller.

That means the 1/Gain is the proportional band, or put it another way, you can make something like 10 degrees from ambient be 100%. Changing the P constant changes the output some percentage wise.

Even though a light bulb is a non-linear load, you can still use it as a load to SEE the effects. A voltmeter should work too. So, should the temperature of your basket, but you can no longer use the controller to measure it.
Thus, you can see what the parameter T actually does.

I did this weird thing in an environmental chamber where I used the proportional band of the chamber ambient to control the surface temperature of a plate, I ran a second PID (my own design) that kept modifying the setpoint of the e-chamber to keep the plate temperature constant. the e-chamber temp was a maximum 10 degress above the surface temperature at 200 C. The chamber had a range of -80 to 200 C,

One of my first designs (in the 80's) was a controller with recipes written in Fortran (It took 2 of us 9 months to complete) was a controller that did voltage, current, power, temperature control, effectively simultaneously.
Actually one was taken as the controlled variable and the others as limits. We did weird stuff and computer heat-up energy and instituted stability criteria to detect shorted thermocouples on heat up. It was a really cool project.

 

Just a thought....

You should be able to operate the T-controlller as "sort of a variac" by shorting the thermocouple input with a wire. If the TC range includes ambient, then the temperature will be ambient. With I and D zero, you just have a proportional controller.

That means the 1/Gain is the proportional band, or put it another way, you can make something like 10 degrees from ambient be 100%. Changing the P constant changes the output some percentage wise.

Even though a light bulb is a non-linear load, you can still use it as a load to SEE the effects. A voltmeter should work too. So, should the temperature of your basket, but you can no longer use the controller to measure it.
Thus, you can see what the parameter T actually does.

I did this weird thing in an environmental chamber where I used the proportional band of the chamber ambient to control the surface temperature of a plate, I ran a second PID (my own design) that kept modifying the setpoint of the e-chamber to keep the plate temperature constant. the e-chamber temp was a maximum 10 degress above the surface temperature at 200 C. The chamber had a range of -80 to 200 C,

One of my first designs (in the 80's) was a controller with recipes written in Fortran (It took 2 of us 9 months to complete) was a controller that did voltage, current, power, temperature control, effectively simultaneously.
Actually one was taken as the controlled variable and the others as limits. We did weird stuff and computer heat-up energy and instituted stability criteria to detect shorted thermocouples on heat up. It was a really cool project.

Just double checking this.I should put a wire across the two thermocouple terminals and change I and D to zero.Does this mean the thermocouple probe is now doing nothing?How accurate would you expect this to be compared to the pid?
When I have been making changes to the settings on the pid should I be waiting for a period of time for the pid to settle down say 5 mins of so before adding the water or does it not matter?

 

You has "T" set to 33, so i would expect waiting al least 5 time constants or 5*33 seconds. I T were 1, I'd consider waiting 5*1 or 5 seconds. If my understanding is right, you want a low value of "T". Stuff with a higher thermal mass can have a high value of "T".

The point is, you have been given a "Radio" and you have been tasked to "make it play". So lets find out what the knobs do by themselves

there's the P or proportional temp controller
The PI controller
and the PID controller.

There's also a variable voltage source, e.g. A Variac.

We can make an ersatz Variac by making the controller think the temperature is ambient temperature.
That "short method" is a "quick test". It doesn't work if the controller has a range of 200 C min to 1200 C min and it doesn't work if it's not a thermocouple.

You probably figured out early that red is negative in this world of thermocouples.

By disabling I & D, you can see the effects with "T" (1-100 s) and (Ambient-x); the max x will be affected by P
A light bulb as a load let's you "see" what's happening. I'm expecting at "T"=100 you would get blinks and when T=1, you won't see the blinks. You might find out that with 10% power, the container goes to 300C and that's not good. So, it's an educational tool.

I used to use a 500 Watt incadescent lamp with the thermocouple on top of it when i was fixing controllers. I could see it. It was much more intuitive.

There's a lot here than just twiddling knobs and there's plenty of stories where some guy was playing one night in a Fortune 500 company and got a process extremely stable,but by next morning he removed his changes to the chagrin of the boss.

I convinced management to get controllers with Analog out and in some I even added the option. We bought enough stuff that we had schematics. At the same time,we normalized the option set.

The options on these controllers were absolutely nuts.

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In the wacky shorted mode, the TC is doing nothing, The temperature of the environment of the controller is measured which is related to nothing.
Say the PB is 10 deg and ambient is 25C. 26 raises the output 10% and 36 raises it to 100% By looking at a light bulb, you can see what 10% and 100% is. It will surprise you and it will be affected bt "T".