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Vernonv
29th Jan 2016, 07:41 AM
Hi All,
I picked up this Gallenkamp muffle furnace the other day and have been having trouble working out what one of the controls does.

It's the dial on the bottom right. It's graduated 1 to 100, but has no marking on it about it's function. From the little testing I have done, it seems to turn off the element when the dial is below 70.

I have emailed Gallenkamp (Weiss actually) and because of the age of the furnace they did not have any info available.

Anyone come across these furnaces before, or might have an idea about what this dial does?

Thanks.

RayG
29th Jan 2016, 08:44 AM
Hi Vern,

On similar furnaces, that is the percent on-time. Some times they are burst fired scr's.

I'd replace the controller with a digital PID temperature controller

Digital PID Temperature Controller MAX 40A SSR K Thermocouple Cable 0 400℃ | eBay (http://www.ebay.com.au/itm/Digital-PID-Temperature-Controller-max-40A-SSR-K-Thermocouple-Cable-0-400-/231652103563?hash=item35ef8a958b:g:7fgAAOSw~gRVzCiV)


Ray

Vernonv
29th Jan 2016, 09:13 AM
Thanks Ray.


I'd replace the controller with a digital PID temperature controllerYeah I was thinking about doing that, but I must admit I do like the look of that old school temp gauge. :)

Ultimately I probably will go for the PID controller.

Vernonv
29th Jan 2016, 09:43 AM
I was just looking at those cheap PID controllers and they all seem to be rated 0-400ºC.

Now I'm not sure if that is the rating of the supplied thermocouple, or if that is the actual controlling temperature range ... most of the PID controllers I have used (it was a long time ago, mind you) would control most any temperature and the range was determined by the type of TC used.

RayG
29th Jan 2016, 10:15 AM
I like the old style temperature indicator too, that would be worth keeping.

The temperature controller I linked to was just the first on the list, you might find a better one at a higher price, maybe even go for a programmable ramp/soak type.

I ended up with a SET64rs ( same as JLD634) controller and a heavy gauge K type in a ceramic sheath.

The cheaper ones might have type K thermocouples, but the packaging limits the maximum temperature.

swarfless
15th Mar 2016, 02:45 PM
Hi Vernon, a bit late coming in I guess. That 'unknown' dial of yours is most likely a 'simmerstat', that was the control most often linked to the old galvanometric controllers. Think of it as the ramp slope controller, it's a bimetal switch whose 'on time' is controlled by the dial position, just cycles on-off indefinitely..till the power is off.

Vernonv
15th Mar 2016, 03:27 PM
Thanks Swarfless.

I ended up buying a small PID controller to replace the large black dial controller and it is using the original control's thermocouple. The "simmerstat" as you call it, is still fitted but not wired in.

The PID controller seems very accurate and works well.

I spent a few hours, a few weeks ago, casting a lot of my scrap aluminium into muffin shaped ingots. :)

I've got a project in mind, but just don't have the time to execute it just yet.

swarfless
15th Mar 2016, 04:31 PM
No sweat Vernon, I have a very similar muffle furnace to yours, gets used mainly for heat treating aluminium & steel. Since the thermal inertia of the furnace itself is the most significant factor my simmerstat is always set at 100%, in other words I might as well short it out. I've been meaning to get a PID controller for over 30 years now, but then I've only had one 'overshoot' disaster in all that time. Guess I've got to know the old controller. You won't regret the PID, set & forget! Well after it's tuned itself to your furnace, eh.

Vernonv
15th Mar 2016, 05:37 PM
You won't regret the PID, set & forget! Well after it's tuned itself to your furnace, eh.Very easy to use and tuned itself very quickly ... pretty much hit the mark and kept the temperature variation tight (I seem to recall it was around +/- 1 or 2º at 720º).

China
15th Mar 2016, 06:52 PM
A bit off the subject, I am about to build a small bench top furnace, any one have plans or know of any plans I can beg borrow or buy