I have an oven that I need to use for some non-standard things. Without getting into too much detail, there is a custom requirement for some temp modules with thermistors. They need to be compared against an accurate probe that will be placed next to them. The bottom line is that the oven has a low accuracy vernier with 0 - 10 (no actual temp settings).
Anyone familiar with retrofitting ovens with digital controllers. Is this fairly easy or impossible, or depends on the technology of the oven? I'll be doing some research, but wanted to see if anyone here may be an expert on this. If so, PM me, and we can discuss. I have a Eurotherm 2208e controller (new in box), and the oven is a Precision Scientific AFO 135.
In most cases, the temperature of the oven is immaterial. You're not using the oven as a standard, it is merely a source. The important characteristics are gradients and stability. Your standard will give you the temperature value, not the oven controller. You'd be better served with an oil or water bath at these temperatures, and if you really have to use an oven you should make your own isothermal block for it. This will help to control the gradients and instability of the air temperature. Years ago I put together a simple system by getting an old lab oven out of the surplus yard, and then going to a metals recycler and buying an aluminum block that I drilled for probe insertion. I installed a 4 wire RTD element in it, characterized it, and used it for years for T/C calibrations.
we deal a lot with ovens, and is very easy to retrofit them. we even do temperature mapping on them. it is important to know the kind of oven you have (gravity oven, force air oven or recirculating oven)
in a short. you need two temperature sensors. one for controlling and the other for safety (over heat protection). but I need more specifics
This is a Precision Scientific (brand) model AFO 135. It is a convection oven with mechanical temp control. We have an odd, non-standard calibration process we need to use it for. It has a very simple zero to ten knob on the front, and not temperature readout. I can set it to some unknown and keep bumping the dial until I hit the vicinity of a setpoint. We have about three or so setpoints in the vicinity of 35 to 100 Celsius. I don't have to get to the exact setpoint. I can get to approximate, then use a comparison sensor (100 ohm RTD probe connected to Hart 1521 meter). So we're trying to figure out how hard it would be to replace the 0 - 10 knob with a digital controller. I have a Eurotherm 2208e that we had in spares (brand new in box). Just the process of figuring out how to modify the control circuitry to accommodate it. We have an engineer working on it, help from Eurotherm (maker of the controller), copy of the wiring diagram, and another offer of assistance from another PMEL forum friend. I am crazy busy and have to do lots of cals while this high priority project has to get done at the same time.
here is what you do, leave the existing 0 to 10 dial as an overheat protection. set it to the max temperature you want the oven to never go pass. in the oven cut a hole for your Eurotherm 2208e. attach the 100ohm RTD in a good spot on the oven, preferable near the center and run wires to the controller. disconnect the power wires that go to heaters and connect them to the controller and the output from the controller go to the heaters. program the tuning and set points in the controller and you are done.. that's the basic idea. when you actually do it. review the manual for the controller in proper wiring, there are different ways to wire the oven (single phase or three phase) and also some controllers can't be wire directly to the oven heaters, they can't handle the amps and need a shunt.