PID as a Thermometer Question

[Ohio-Ed]

I now have 3 inconsistent / inaccurate kitchen type digital thermometers and am ready for an upgrade. I don't mind spending the money on a decent thermometer but was wondering about an alternative... For the price of a Thermopen, I think I could get a PID and either a thermocouple or RTD sensor. I am considering going electric eventually and thought a PID would allow me to measure now and control when I'm at that point.

I'm thinking of one, maybe more PID's in a box used initially as thermometers.

I know I would have to come up with a box and power and all but does this idea have merit?

I have no experience with PIDs so I'm looking for some input...

Questions:
Is a PID going to be more accurate than my POS cheap thermometers?

I can't find a way to calibrate the cheap thermometers I have now... can a PID be calibrated?

I'm thinking that to be most versatile, I should get a PID capable of controlling a SSR... agreed?

Thermocouple or RTD or...?

Any PIDs that would allow me to "see" two inputs simultaneously?

Manufacturers / Models you suggest, or suggest I stay away from?

Thanks for any help.

 

[samc]

A popular option is auberins.com, Temperature control solutions for home and industry
I considered using this stuff but went with a BCS which is overkill for what you want now

 

[jwright]

Ohio Ed,
I agree with you about moving towards thermocouple/pid now for later expansion.
I don't know if you have considered starting with a cheaper, stand alone device that will use the thermocouple probes. You won't be wasting money on any probes purchased, and when you do upgrade to a PID, I'm sure you will have a need for a second temperature reading device (ie reading sparge temp while monitoring the mash).

Two well reviewed choices are below. I think I have looked at about 100 pgs (Evan!) here of thermometer issues, and I'm down to one of these choices. fyi ,there is some discussion of thermocouples not being an inherently accurate technology at our temperatures, but no users here seem to have issues.

adjustable -
Handheld Thermocouple Meters And Cole-Parmer Workhorse Thermocouple Thermometer - Cole-Parmer Catalog

ThermoWorks – MTC Mini Handheld Thermocouple

New JMS Type K Thermocouple Thermometer with 36" sensor - eBay (item 230376065988 end time Sep-19-09 10:53:45 PDT)

You wouldn't have to put together the PS, box, etc and you could use this for cooking or other activities with a simple probe swap.

 

[Ohio-Ed]

Guys, thanks for the feedback

Samc: I looked at the stuff on aubreins.com and that is the direction I am leaning, I was just hoping to hear from some folks that have hands on experience. Between controllers, sensors and probes there are a lot of choices and it is hard to get a real grasp from reading the short descriptions on the web sites. I have also looked at omega.com, ebay and a few others...

jwright: I have considered another, better thermometer than the ones I currently have, but I have also read many pages of folks having problems. Thermoworks appears to get the best responses from the reviews I have read.

I am a tinkerer... I'm probably closer to an electric HEX or Boil Kettle than even I can predict. Panel mount thermometers (the few I have seen), appear to be more expensive than PID's which makes me wonder why. Is a PID and sensor more or less accurate and stable than a Thermopen (for instance)?

Thanks for any help,
Ed

 

[CodeRage]

What is going to affect accuracy the most is the probe not the display device. The display device is only as accurate as it's ability to be calibrated to the probe. I have 4 auber PIDs on my rig, one of which is for measuring temps in the mash tun. Like you have found, PID controllers are cheaper than dedicated panel mount indicators. Perhaps the more expensive panel mount displays have more calibration options. I don't have much experience with them but I imagine kladue might be able to tell us.

What I do know is that RTDs are more accurate than TCs. Here is a page with a table for class B RTDs (like auber ins sells) and their accuracy across their operating range. I believe Class A's are 2x more accurate than a B.

RTD Elements and RTD Probes - Resistance Temperature Detection Sensors(RTDS)

With the PID controller I can zero the calibration by adjusting a temperature offset variable. So I have mine adjusted to read 212 with a rolling boil at sea level. I like to have mine calibrated this way because a, the temp is considered to be a constant and b, it's closer to my mash temps than zero. I can't say that this makes it more accurate for our application but it makes sense to me.

 

[Ohio-Ed]

CodeRage, thanks for the input!
My thoughts are to build a temporary panel to gain some experience with PID's, sensors, probes, etc. The current "burr under my saddle" is the inaccuracy of my thermometers with no way to calibrate. Based on the reading I have done, it appears that RTDs are more accurate and don't require special signal wire. And it sounds like the Auber PIDs can be calibrated. So, with an Auber PID and an RTD probe, what kind of accuracy can I expect in "measuring" temperatures? +/- 1 or better? Does the additional cost of RTDs make up for frustrations from TCs?

Thanks,
Ed

 

[CodeRage]

No problem.

They really aren't that much more expensive than a thermocouple. Here are some brief accuracy values in *F.

Class B
+/- 0.54 @ 32.0*F
+/- 1.23 @ 170.0 *F
+/- 1.44 @ 212.0*F

Class A
+/- 0.27 @ 32.0*F
+/- 0.62 @ 170.0*F
+/- 0.72 @ 212.0 *F

So with a Class B you will be within 5/4 *F of your target and around a half degree with a Class A.

I opted for the Class B with disconnects, it's nice to be able to unclip it from the MLT so I can dump the grain in the compost bin and hose it out without having to remove the RTD or disconnect it from the PID controller. The 10 bucks extra was worth eliminating the head ache of dealing with it every time I needed to clean the MLT and BK.

Now here is the funny thing. My RIMS controller has a type K TC in it (Its all I had on hand). and it seems to do okay, I just adjust the temperature control on it according to my mash tun RTD. Usually it is with a degree of MLT temps. I do plan to replace it with an RTD eventually.

Auber does have a Class A but you will have to build your own thermo-well for it.

 

[jwright]

Ohio-Ed,
Your 'idea' has been banging around in my head since I first responded. Are you planning on initially mounting the PID in a small enclosure for portability, with AC and probe jacks? I wonder how much the AC cord tether would be a pain, depending on one's layout. I'm begining to think this would be a great way to get to start playing with the "cool" toys.

jason

 

[Ohio-Ed]

Jason,
That's exactly what I plan to do.
I'd like to build a temporary panel/enclosure to get some hands on experience with the controls. I am already committed to having AC in the brew area because of pumps so, the cord, GFCI and all is no big deal. I'd like to have multiple probes to monitor temps in the MLT/HEX, HLT, and BK (because I currently use the BK to heat for the HLT). I may initially have more thermo wells than probes but would like to have at least two active probes. My brewing equipment is kind of Lego like... I have a couple of small stands that I use and almost nothing is bolted or welded together. Everything has QD's. My pumps are mounted on a portable stand. Right now I heat with propane and like that because of portability, but with the modularity I'd like to be able to swap in an E-Keggle.

CodeRage: In looking at Aubers PIDs is there a benefit/need for the Ramp/Soak features? Looks like this feature just about doubles the price and I'm not sure if it is generally needed for the processes we deal with in brewing. Also, I see what you mentioned about no thermo wells for the Class A RTDs... disappointing. I might be able to get something from BrewersHardware.com. I like the metal disconnects for the RTD probes ($3.50/ea), I assume thats what you were talking about for being able to unplug your MLT?

Thanks
Ed

 

[CodeRage]

I have the liquid tight ones so half of the connector is built into the bulkhead fitting. Those will work though.

If you are going to do step mashes and don't want to have to get up and change the setpoint from time to time then a ramp soak is what you want. Otherwise, change the setpoints manually. The time spent programming the ramp and soak schedule may take longer than getting your butt off the chair and back Thats how I looked at it.

 

[Ohio-Ed]

CodeRage: I'm sorry if I'm being a bit thick headed but... When you disconnect your MLT, is there still a wire hanging from the vessel or is the probe disconnected AT the vessel? When disconnected is there a hole in the vessel? I'd like to be able to start with a probe or two and move them between vessels then just add probes as I get tired of moving them. So, it sounds like you did not get the PIDs with the ramp option. Thats the way I am leaning to start... that way I can claim I'm getting some exercise by gettin my butt out of the chair to reset temp controller. Thanks for all your input, the picture is becoming clearer

 

[CodeRage]

Its all good. Here is a pic of the liquid tight RTDs

As you can see the threaded part of the probed goes through the mlt wall and is held in place with a 1/4" NSPT nut and gasket. One side of the disconnect is attached to the probe so there is no pig tail or anything hanging from the kettle.

 

[jwright]

CodeRage,
I am looking to use a disconnect for my RTD or Thermocouple. Some of the models I have looked at have a metal braid covering the wire but do not specify if there is an inner insulator or what the temp max of the cable is.
I am planning to initially heat the HLT with gas to get up to temp, and feel I will need some heat protection. At $30 a pop, this isn't something I want to experiment with.
What do you think about adding a fiberglass then metal braid covering, or swapping out the connecting wire of the disconnect RTD with the insulated, braid covered wiring of one of thier cheaper RTD? Or have I missed an easier solution?
thanks
jason

 

[Ohio-Ed]

I am ready to order a PID and a couple RTD sensors from Auber to get my feet wet but had a question...

Does anybody know the difference between these two PIDs (Model: SYL-2362 & Model: SYL-2352):
http://www.auberins.com/index.php?main_page=product_info&cPath=1&products_id=106

and

http://www.auberins.com/index.php?main_page=product_info&cPath=1&products_id=3

If I'm planning to use an SSR later, what am I giving up by buying the Universal PID vs the SSR Specific PID? Unless I'm missing something, looks like the Universal just adds an additional built in relay output option.
Does the Universal support % Power output?

Thanks for any input.

 

[CodeRage]

jwright,
I think the silicone insulator that comes with the RTDs from Auber is sufficient as long as they are not mounted close to the burner. A fiberglass jacket from mcmaster would be cheap insurance.

Ohio-Ed,
I think that IS the only major difference. In the boil kettle it is nice to set manually set the output, if it is for the Mash then you probably wont use it very often.
I went ahead and got the dedicated SSR version for all mine so if I had a spare or had to order a replacement, I couldn't screw it up.

 

[Ohio-Ed]

CodeRage,
Thanks for the reply.

I had my order ready to go at Auber when that question popped into my head...

I just talked with the folks at Auber and they told me they have added Manual control to the Universal PID but it is not as easy to use as the SSR model. He also said the SSR model has fuzzy logic, the Universal does not. He said the SSR model has more functionality but is also more complicated to use. He also mentioned it was more accurate?

I think I am going to go with the SSR model and see what happens.
I'm going to order the PID, a Liquid Tight RTD, a Class A RTD, a 40A SSR and a Heatsink. That should get me enough to start playing.

Next on the agenda to start thinking about... How to build a free standing 5500 watt portable heating element with a built in RTD sensor and level sensor to prevent dry firing. That way I can stick it in my Propane kettle (or anyone else's) or HLT.

 

[CodeRage]

IMHO, I would build a dedicated HLT. something that can be moved from one pot to another means the leads to the element are going to be somewhat exposed to the water. If I really had to, I would make some kind of HEX with a pump. Toss some tubing on there for the inlet and outlet. Maybe make some kind of stainless plate or fixture that you can mount them and the probe to. But, the liquid tight probe isn't submersible.
Thats alot of cash though.

For the liquid tight RTD you can get the 1/4" stainless nut and silicone o-rings from bargainfittings.com .

 

[Ohio-Ed]

The portable electric heater thing is an idea that just came to me today so I haven't really thought it through. As I said before, my "System" is ultra modular (think Lego's). For instance, I built a HEX coil & manifold with QD's and thermowells on the input and output that hangs in a kettle instead of being mounted in it. This weekend, I dropped the same coil in a bucket of ice water to finish cooling after my CFC got me near ground water temp.

My thought for a portable heater would be a tube structure that is both a frame for mounting the element & sensors AND acts as the conduit for protecting the connections & cables. I'm thinking of a large tube with T's and element & sensors mounted in the T's via threaded or compression fittings. I'm picturing the tube structure also acts like a roll cage to protect the element and the walls of any vessel (even a cooler) it gets dropped into. The same heater/control/sensors/etc could be used in the HLT then just moved to the BK.