Panel Mount RTD connectors

Does anyone know how sensitive the RTDs are? Meaning, will running them through some random connector mess up their accuracy?

I need to get a panel mount connector for the RTD in my HERMS, and really don't want to buy the one from Auber unless I have to because I know I'll be overpaying for it.

I just don't know enough yet to select a suitable/identical yet less expensive connector from somewhere like mouser.com or even ebay.

Is there anything special about the connector?

Any good quality discrete connector with 3 (or more) contacts would work ok. You just want to avoid any resistance through the connector, as of course that would throw off your sensed temp. Thermocouples are a different matter, and the proper, type-specific connector MUST be used. McMaster has male and female for about $14 a pair, but I didn't find a panel mount RTD female.

What are you finding cheaper than the $3.50 or whatever Auber charges?

Boerderij_Kabouter said:

What are you finding cheaper than the $3.50 or whatever Auber charges?

Click to expand...

Well, like I said, I haven't started looking yet because I didn't know what to look for at this point.

My comment about over paying is just based on the other items I have purchased for my HERMS system (PID, SSRs, heatsinks, 4" RTD, and definite purpose contactors). Looking around and buying them from various sources has saved me a considerable amount of money vs. buying from Auber.

The thing that's nice about the ones at Auber is that it is the same type of connector as on the RTD as well. They are small, simple, and work great. I got mine as part of a larger order so the shipping was negligible.

Even ignoring shipping, auber's prices are high on many things, IMO.

It would have certianly been easier and more convenient to just order everything from them and not spend time searching around, but I was in no rush with purchasing, so I opted for the savings.

I've got no problem ordering from them if they have a good price, I was just wondering what it was that I needed to look for in order to shop around. It sounds like low resistance is really the thing of concern with an RTD.

I'll poke around a little to see what's out there.

edit: I am not trying to bash Auber. Sorry if it came across like that (and re-reading my first post, I can see how it might have seemed that way). I just want to shop around based on previous price comparisons I have done.

In that case you are correct. You just need low resistance that is all. RTDs work on a resistance difference at the probe, the wires just need to accurately transmit electricity from the probe.

Would one of you that has one of them mind measuring the reistance of it, just to give me a ballpark figure?

I'm seeing 3-wire connectors that measure less than 20 miliOhm @ mouser.

On a somewhat related topic...

The manual for my PID and a few posts on here talks about how to connect the RTD and mention 2 red wires and 1 white wire, but my RTD has 1 red, 1 blue, and 1 yellow.

I found a couple of ways to connect the 3 wires of the RTD and get what looks like a correct temp reading, but has anyone else seen an RTD with the three colors like mine has?

If you calibrate it with the connection in place, what does the resistance matter?

Auber's support is phenomenal. Every question I've e-mailed - even on weekends - has been answered w/in an hour. I'll give 'em a little slack in the price dept. for that.

klyph said:

If you calibrate it with the connection in place, what does the resistance matter?

Click to expand...

I think the calibration of a probe on a PID just allows you to set a static offset value in degrees. That might work, but wouldn't that rely on a linear resistance curve for the RTD?

Meaning, a 1 Ohm added resistance from the connector might be equal to 1*F degree in ice water, but that 1 Ohm at 150*F might be equal to more or less than 1*F.

or am I over thinking things?

You could be right, but it would be easy enough to test.

Add a resistor to the probe, test in ice water and boiling water, compare to readings without resistor...

Maybe I'll just make some beer and stop thinking about all of this.

jkarp said:

Auber's support is phenomenal. Every question I've e-mailed - even on weekends - has been answered w/in an hour. I'll give 'em a little slack in the price dept. for that.

Click to expand...

Agreed. I got confused one day on the PID v PID w/SRR v w/contact... I called them up, said it was for beer, and the guy basically said "dude, this is what you want"...

It was very refreshing.

RTDs put out a (for our purposes) 100ohm to 138ohm resistance range of 0 to 212F. thats .18ohms per degree. Using that as a reference you can figure out a given connectors resistance will affect the temp reading.

Depending on the circuit used to measure the RTD, a line resistance compensation circuit can be added to subtract the additional resistance. This is why some RTDs come in 3 to 5 wire configurations. You couldn't do this with just 2.

Unless the documentation says it compensates, if it has more than 2 terminals to connect the RTD it more than likely does.

What are you finding cheaper than the $3.50 or whatever Auber charges?

DITTO-

I use one. I purchased everything from Aubers and SUYI (owner) walked me through the setup and everything.....

I've used theses small microphone jacks when I didn't want to wait... but cheaper... don't think so?

http://www.radioshack.com/product/index.jsp?productId=2103996

The awesome thing about Aubers quick disconnect is just that...it is a quick disconnect (like an air fitting). I will never buy from another vendor..I am sold on his customer service and pricing!

i used the same ones as ohio-ed. i had planned on going with XLR audio connectors, but just happened to come across these while at radio shack.

p.d.

Jason (CodeRage) is correct. If you are concearned about the extra resistance buy a four wire RTD. If works similarly to the sense lines on a DC power supply which compensates for any extra resistance in the leads or another example would be the 4 wire ohms measurement on a multimeter.

I bought the Panel Mount connector for RTD sensor from Auber but haven't used it yet. If I were to clip the RTD wires and put this in line for a quick connect, how would one go about making the connections? solder? which posts are which?

Solder. The posts don't mater as long as the transmitting stays consistent from sensor to input post (e.g., on you PID). I used pin 1 for white and pins 2/3 for the red wires.

So, I went ahead and ordered the connector fro Auber last weekend and it arrived in just a couple of days. I was under the impression that it came with the "inside the box" wiring included, but it didn't. Just the male and female parts.

So, I went to Lowe's to see if they had some suitable thin wiring to use and it looked like CAT5 cable was most suitable. I've got a box of unused ethetnet cables at home, so I didn't buy anything and just left.

But, on the ride baclk to my office I had a "Doh!" Moment. CAT-5. Of course!

I've not only got cables lying unused, but also a couple of wall plates I didn't need that came with a DSL modem.

8 wires in that cable. Enough for 2 RTDs in a single cable that would easily 'snick' into the connector and stay put.

I'm not going to use this since I already have the Auber connector, but if I ever build another system...

minute amounts of resistance can have a detrimental affect on an RTD reading. I would rather have a pin connector versus a spring and contact personally. Not saying it wouldn't work, just that I wouldn't use it

I agree that if the connector isn't suitable, then it isn't suitable. The thing is, I don't know how much resistance is seen through a cat5 connector *or* my auber connector. For all I know, they are on par with one another.

If I feel motivated, I'll measure them both tomorrow, just for grins.

I will say that, with out ANY connector in the path, my RTD had a 3.2*F error (checked in crushed ice water and boiling water), which I had to offset with the PID settings.

I used RC model airplane gold coated pin connectors, resistance was down to below the meter could read, this on a Fluke 87 not 88 which can read down to 0.01 ohms. Dissimilar metal contact alone at the connector would throw your low resistance probe readings off. With BCS controlled units they require 10K ohm probes, jacks or audio connections would be not a problem with their small added resistance vs 10K ohms in ratio on temp readings.

One feature of 3 and 4 wire RTD circuits is the paralelled connections( 2 red wires, or 2 white wires) are used to cancel the resitance effect of extended field wiring and connectors, in the measuring circuitry by making paralelled wires part of a wheatstone bridge.

Thanks Keven as I was wondering why the reason for 4 wire this explains it.
Now back to work. LOL!

kladue said:

One feature of 3 and 4 wire RTD circuits is the paralelled connections( 2 red wires, or 2 white wires) are used to cancel the resitance effect of extended field wiring and connectors, in the measuring circuitry by making paralelled wires part of a wheatstone bridge.

Click to expand...

Ok, I thought I had read this before, but wasn't sure if I was making imagining it or not.

So... given that I have a 3-wire RTD (and leads that are under 6 feet long), it sounds like the connector isn't very critical.

Thanks, kladue.

In the industrial instrumentation field we can run up to 1,000+ feet of sheilded wire to 4 wire RTD's, the largest problem is electrical noise pickup not resistance in long runs.

ROFL!

We had a non union contractor use our conduit run for his low voltage control wire run. Way up high in a hidden area at a 2" LB we placed about 30 wraps of #14 wire around his control wires and applied 70 VDC. All his insturnent metering at the panels were useless. Contract bid without installing conduit cutting corners cost him plus getting caught. Yes outside noise, longer the run with parallel conductors the greater the risk.

Can you run two of the RTD quick connectors to the same PID RTD input? So I could use the same PID and control box to run the hlt and bk (not at the same time of course)/

I'm bot sure I follow you here. The pid can only support one probe at a time. You could have one connector on the panel and swap which probe was plugged into it, I suppose.

But, more importantly... Why do you want a probe on the kettle? It serves no purpose.

Can you not set the pid to say 212F on the kettle? and that is what I meant to say two probes two ports and one pid (can two ports be connected two the same pid input without any interference?). I see alot of people here running the pids in manual for the BK but I really dont get that why not use them with temp control? I think it would be nice to see the and control the temp of the boil. I am just curious.

No, you can't do that reliably. The temp of boiling wort is a constant, be it a low simmer or a geyser boiling over all over your brewery.... It's the same temp.

you want a pulse modulator for controlling a boil, which is what the PID "manual mode" is doing. And you don't need temp feedback to the PID in manual mode.

Still curious....If a PID can control the hlt temperature (that being the most crucial in the system) why cant it hold the boil at say 208-215 range? The environmental chamber I pulled this off of is very precise in the plotted measurements I would think that it could hold a temperature setpoint.

Like walker said, the difference between low simmer and volcanic geyser cannot be determined by the sensor probe. As the liquid reaches boiling point, vapors carry heat energy away. This means the liquid part remains 212 though the rate of evaporation may vary tremendously. The system will either apply way too much heat and induce exponential vapor production (boilover) or it will hit boiling, turn off, hit boiling, turn off, ad nauseum.

It's a a matter of physics, because you are operarting at the point where some matter (the wort) wants to change from a liquid to a gas.

Straight water at standard pressure boils at 212*F. It won't boil at all at 211*F, it is is physically impossible to heat the water to 213*F, so forget about a "range" when boiling. It happens at one very specific temperture.

A PID could just turn the element on 100% of the time and it would maintain a boil at exactly 212*F. It would be a violent boil, but it would be a boil. That's not what you want.

Feel free yo try it if you want.

So it is the boiling point itself that causes the problem and the PID has no problem with maintaining a perfect say 170F? That has been puzzling me since I started my research. Thanks for the answer.

That's correct.