Ramp/Soak PID controllers?

T

thyNemesis

Joined
Jan 16, 2013
Messages
3
Hello everyone,

I'm starting to convert a used kiln into a heat treating oven and I'm about to purchase a PID controller and was wondering if
I would need the ramp/Soak options that are available on some controllers? I would hate to spend the additional money on these
option if I did not need them, or to skimp on the extra cost and wish I would of spent the money on it.

Thanks.
Jeff
 
I got a ramp soak pid from http://www.auberins.com/index.php?main_page=product_info&cPath=1&products_id=4 and love it. It is only $30 more than a regular PID. I can now ramp my oven up with soak times and another thing I like is I can set it to take my oven to say 50 degrees below the target temp and hold it for a bit to let the oven stabilize close to the deired temp then slowly run it up that last little bit and not have to worry about overshoot and know my steel isn't lagging behind the thermocouple. Also if I want to anneal a complex steel that calls for something like a 50 degree drop every 30 minutes, I can set it up and go to bed knowing in the morning it will be taken care of with out going out and resetting the temp all the time. No harder to hook up and lots more abilities and options for the price.
 
Spend the extra and get the ramp soak and you will never second guess yourself. Its not really that much more.
 
I used a basic (no ramp/soak) controller on my first oven. I have built 4 more since with ramp/soak controllers and would definitely say they are worth the extra money (I pay for the ramp/soak units, but have several of the more basic units in my store of scrounged stuff).

The units I've been using are the Omega CN7823 http://www.omega.com/pptst/CN7800.html

or the AutomationDirect Solo SL4848VR http://www.automationdirect.com/adc...ers/1-z-16_DIN_Size_(SL4848_Series)/SL4848-VR

They are both the same controller with different badges, at least as far as I can tell.

I can't comment on the Auber Instruments units because I am in the UK and have not tried them (both AD and Omega have UK suppliers).

I did spend quite a long time looking for suitable controllers at an affordable price before settling on the AD unit. I use process controllers at work, so I'm reasonably familiar with controllers in general.

One thing I particularly like about the AD/Omega, is that it can autotune at 4 different temperatures and will then automatically select the set of PID values for the tuning temperature closest to your target temperature. I find that the optimum PID terms for each oven are different at Austenitizing and Tempering temperatures, so this actually gives better control over the full range than just having one set of PID terms. I'm also (still) intending to build a tempering-only oven to work off the same control box and eliminate the need to wait until the main oven cools before I can start tempering.

If money is really tight and you are only going to be treating the simpler steels for a while, you can fit a cheap basic controller from ebay and upgrade to the ramp/soak controller when you need it. Terminal positions may change, but the wiring is otherwise exactly the same for ramp/soak as for a basic controller. Stick to a 48mm x 48mm unit and allow an extra 2 inches of length on the wires to accommodate any changes in length or terminal layout. Like most other electronics, controllers tend to get better and cheaper with time.
 
Well, I've decided on spending the extra money for the ramp/soak controller now instead of buying a cheaper model and upgading later.

Thanks for all the valuable input!
 
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