Oven Controller with Set Point Output

The Watlow, is a pretty reasonable cheap device.

For a temperature verification, you'll need some more control, with an RTD and possible a displat screen.

Its pretty hard to program out sloopy/lazy operators though.

It looks like the Watlow F4 has the capability to retransmit the setpoint and/or process variable as 0-10V or 4-20mA. You might need both to make sure your oven has actually reached the setpoint - or use a deviation output alarm point. You didn't mention your controller output requirement, so you'd have to check that. Obviously, there are many other ways of accomplishing this - PLC, etc.

As far as keeping it simple, I think you're past that point . I see a database of temp vs barcode being needed, and if this info already exists somewhere else, you'll need to access that, otherwise the two will be out of sync before you know it, and who gets the blame then?

Is there a way of reorganising the workflow such that a batch or a campaign of items are baked at one temperature before the oven is reconfigured for a different batch or campaign, rather than have the temperature setting dance about all over the place?

Just askin'.

We are a job shop, so work flows through as it arrives. Our method of organization is having a few ovens that run at the same temp all the time and the rest that are reset as needed.

Mike W.

Here's how I envision accomplishing your task. You would need:

A. Temperature Controller with retransmit capability of Setpoint and Process Temp. (maybe Watlow F4, as mentioned earlier)

B. Central Processor, could be PC, PLC, etc, with:

Inputs: 1. Barcode reader, 2. Setpoint (SP, from Controller), 3. Actual Oven Temp (PV, from Controller)

Outputs: 1. Not ready light (or oven door lock), 2. Ready light (or unlock the door)

C. Program 1. Turn Not Ready light on, 2. Product detected (by barcode scanner), 3. Read barcode, 4. Get required temp (RT) from RT vs barcode table, 5. Get Controller Setpoint (SP), 6. Compare SP to RT [If <>, go to 1.], 7. Compare |PV - SP|< tolerance for enough time for oven to stabilize, 8. Turn Ready light on and set timer to give operator time to load furnace, 9. Go to 1.

Obviously, this is rudimentary. For example, time could be saved if the oven 'soak' time was continuously monitored so the wait interval could be eliminated if the oven had previously been at the RT.

These Watlow models, like most controllers (TOHO, Shinko) display the setpoint as well as the process value. Is this suitable ?

I need the controller to output the setpoint, not just display it. The Watlow 93s that we use now display the set point, but we still get the occasional error.

I need to have two things to compare: What the set point is, and what the set point should be.

Thanks,

Mike W.

A signal or recorder?

I need a signal, because I want to compare it to the required set point for the job.

Thanks,

Mike W.

Does the Watlow coms software provide a solution ?

http://www.watlow.com/products/controllers/specview-hmi-software.cfm

It has great potential.

Thanks,

Mike W.