For Christmas, I received the Sous Vide Magic PID controller - a comparatively cheap method of turning a slow cooker, rice cooker, or hot plate into a temperature-controlled water bath for sous-vide cooking.
I'd like to give my impressions, and also ask a few questions of anyone who has experience with using a PID to cook sous vide.
I've seen a few people mention these devices on other threads, but I don't know how many people actually had one. I was curious if many other chowhounds have one and how they like it - if they find any limitations, durability issues, or whatever.
For my part - the first thing I noticed was that it was not as simple or easy as I expected. The user interface was not at all intuitive - I foolishly tried to navigate it without instructions, managed to miscalibrate its thermometer, change it's base settings, and then lock myself out of the controls, all without any clue what I had done. After a thorough reading of the instruction manual, I repaired my own damage and started cooking.
I also found I did not actually know what a PID does before I got one. I thought I did, but I was wrong. Strictly speaking, you don't actually need to understand what a PID does in order to use it - this one has an auto self-tuning function you can use in lieu of adjusting its settings yourself. But that is not an option for me given the tendencies of my psyche. So... more reading and fiddling before getting started.
On the other hand, though the interface was intimidating and I needed a several-hour long crash course on what a PID is to even figure out how it works, once you get going, it's really easy. Once familiar with the menu, you can set controls in seconds, warm the bath, add the food, and not worry about it until it's done.
I seemed to be able to attain temp control of about +/- 0.6 degrees Fahrenheit with a simple setting and +/- 0.2 degrees with a more elaborate setting using a medium-large sized slow cooker. So precision was more than adequate.
Overall, though the PID was less user-friendly than expected, I can't argue with results. I've now tried several long sessions without any glitches. Its temperature control is impressive. And it's far cheaper than the Sous Vide Supreme or an immersion circulator, even a used one.
Questions for any of you that have a PID:
1. Do you find a circulator is necessary when not stuffing your water bath full? Do some types of heating elements negate the need for a circulator? I understand the theoretical problems with forgoing the circulator, but my experiences with large stockpot + thermometer seem to indicate that it's not a big deal when heating from the bottom. If I do need one, what do you recommend?
2. The manual warns of overheating the PID itself - would, say, a 1000 watt hotplate on 'high' be too much power to plug into a PID?
3. Can I switch from PD mode (integral time set to 0) to a PID setting once achieving a rough stabilization without destabilizing the water bath for a little while?
4. Is there any reason I'd want to set derivative time to zero? The manual pointed out that I could do this and use it as a PI controller. Cool. So... why would I want to do that?