monitoring pressure of a pressure cooker

[Stewart]

Hi,

I am trying to help a client find a pressure sensor and data logger for measuring pressure inside a pressure cooker like InstantPot during cooking. Max temp expected about 125 deg C (257 deg F) and max pressure about 15-20 psi above ambient. The sensor is easy enough to find, but we want to avoid drilling a hole in the pot, so want to combine the sensor (0-5V or 4-20mA as required) with a datalogger in robust housing and magnetically put it on the inside of the lid of the pressure cooker.

Great if said datalogger had bluetooth or wifi to send data out of the cooker, but ok during cooking, but also ok if we only get that data after the end of the cook when the sensor comes out of the pot.

Does anyone know of a small datalogger than can withstand this high operating temperature (most I've looked at can only take 85-90 deg C), high humidity, medium pressure environment, that can accept a relevant external pressure sensor (or has one built in)?

Building an insulating case, somewhat like some oven loggers do, might be an option, but would prefer to avoid cobbling something together if possible, and just buy something fit for purpose. Budget is a fairly minor concern.

Thanks.

Stewart
www.villageinfrastructure.org

[skywatch]

@Stewart Interesting idea, but what would be the point I wonder?

I have an instant pot and so long as it works I'm not worried about it. Having said that, there are options for attaching to or building into the lid, but don't forget that any drilling will void the warranty. Also remember that the lid is dishwasher safe and as such anything you build in or attach needs to be the same.

Also, anything battery powered is going to suffer badly in such hot and humid environment so naybe a small peltier could be used with a harvester to power the logger.

It might be worth contacting some of the industrial kitchen appliance manufacturers to see if they have anything suitable. I'm sure if anyone has one it'll be Bosch or Panasonic.

[Stewart]

Thanks for the reply. The client wants to compare the efficiency of performance of various pressure cookers, particularly if solar powered, as panels and batteries cost quite a lot, for use in very offgrid areas. So it will be a test on 10-20 different cookers and some destruction is fine, but best avoided if at all possible.

Took all day to find, but this looks like it would do the job. Any other ideas welcome.
https://www.madgetech.com/products/pr140/

[skywatch]

@Stewart No problem! - It sounds like an interesting project, but how many people are going to buy 15 100W panels to power a single cooker I am not sure......But that's what I guess you'd need in non-perfect conditions with losses etc.

My Instant pot (6 quart version) cost me £79,99 from Amazon. To solar power it would cost considerably in excesss of £1000..... Is your client Elon Musk?
I think they should instead investigate a series of flat holographic lenses that will concentrate the suns heat and use that directly on the cooking vessel.

[NeverDie]

@Stewart Since your project is aimed at doing experimental comparisons, will you be heating just water? If so, then you can accurately gauge pressure based on just temperature using Boyle's law.

Seems very unlikely that you'd get a wireless signal out of the pressure cooker from inside it when sealed, since the whole thing is effectively a Faraday cage.

You could conceivably use something like a TPMS like the kind used inside automobile or truck tires to get a pressure reading Not sure about the temperature limits of those, but I'm sure at least some of them are designed to handle at least some amount of high heat.

[Stewart]

@skywatch Thanks for the comment. We've already started on this, and numbers are promising. One can cook rice in 20-30 mins, meat stew in an hour or so. Two cooks a day, 3 hours of cooking. There's at least 3 hours a day of solar, if not 4-5. And the key is that, with an insulated pot, one doesn't actually need 1500W - I've done this with 250-500W. At $0.20/W for solar ex-China, that's just $50-100 of panels plus the pot. Double it for a retail price for a $500 solution. At $1/day of fuel cost, pays back in under 2 years. So no, don't need Elon as a customer, particularly if leased to customers for 3 years at $1/day. Thermal cooking has been tried for decades and doesn't work for various reasons. More efficient, yes, but not convenient nor desirable nor automated nor particularly safe.

[Stewart]

@NeverDie Thanks - agreed, wifi unlikely to escape the pot. Will try and see. Will have a variety of foods cooked.

[NeverDie]

I had assumed a pressure cooker would have to be made out of metal, but I see you can buy plastic pressure cookers on Amazon for even just $10. With that you could get the RF out no problem. That makes the whole problem much easier.