Help with temperature sensor


Senior Member
Ok, I have an opportunity to earn major WAF points but I am at a loss how to do this so I was hoping for some direction. Wife wants me to display the temperature of the pool on the touchscreen. We have a solar heater and the controller outside displays the temp, but she wants it on the screen inside. Ok, I guess I have a few options. I prefer to use a regular pool temp sensor that I can put in the PVC like the others. I guess I can get a sensor like the one with the solar controller and try to get it into the Elk and figure out a way to pull the temps, or RCS makes a pool sensor that hooks to their wall display units. Obviously the sensor direct to Elk would be the most cost effective.

If I use the Goldline controls sensor, the sensors specs are here. I know I would have to extend their leads which will probably change the sensitivity and then I am clueless as to how to get this to work. Could I just hook the sensor direct to a zone, set is as analog and build rules to do conversions and come up with temps? Or do I need an A-D converter like BSR talks about? Or is it just not possible to use this like this?

Other option is RCS makes a pool sensor that attaches to their WDUs like the TR16 and TR40. I think I can extend the leads because they say it is a digital sensor and unaffected by lead length. I might use a TR40 anyway as my tstat but if I did I wanted to use the remote sensors for indoor averaging and outside temp. Can I have more than one WDU on the controller, 1 with just the pool sensor and then the main one with 3 remote sensors? And I assume I can read the remote sensor temp into the Elk and grab it with CQC or ML.

Any other ideas or suggestions on how to make this work? I could certainly use some WAFie (like brownie?) points. BSR, Guy, Spanky - anyone...
Being a tightwad I would use a $3 one-wire temp sensor and use one of the free one-wire plugins with HomeSeer. I used one of these sensors in a small test tube filled with silicone to measure temps in my fish tank for the longest time and it worked perfectly until I sold my tank.
Thanks for the suggestion but I need a pipe mount sensor and I don't run Homeseer. It needs to run thru the M1.
Even if I could somehow cover that probe and mount it, 7 feet is not long enough to get to the RJbox in a spot where it could be hidden from the elements. This type of sensor is much better if I could get a way to may it interface with the M1.
Hi Steve

Not a cheap option ....

Would require the following hardware.....

Elk serial expander module , w800 rf receiver device , rfxcom remote temp sensor (see link) you can apparently connect an external dallas sensor to it , but you would need to waterproof it....check out the link for the rf temp sensors ....these do work with the W800....

Hi Steve-

I don't have an Elk yet, so I'm not sure how its analog stuff works, but it seems like it should work .. you may need another resistor to set up a divider. I did see this chart which details the probe perfromance-

temp chart

Maybe someone with a little more experience with Elk analog can answer? All the spec says is it reads 0-12 v.... the temp probe moves quite a bit with each degree of change, but do you need to supply 12v, or does the Elk do that?

If nobody can answer, you could experiment with a couple of potentiometers and figure it out pretty quickly.

Using a direct temp sensor is not easy. Regular bimetal sensors (why is that you dont remember the name when do you need it?) are highly unlinear and RTDs are very linear, but being made of platinum are extremely expensive.

The other problem is the M1. Its limited features regarding analog zones and variables do not help. It would be great to just pull out the voltage, multiply by a factor and add a displacement (T*factor+disp) to show the temperature, but you cant handle variables here. You will have to do a rule for every temp range that you want to show, and trigger ever N seconds. If true, the rule would sends a fixed string indicating the temp range. Very limiting.

I dont know how the Elk own probe works. I think that if you decide to go with the M1 their probe should be your best bet. You might try extending the probe and using the temp correction option in the M1 to fix any error added by the extension wires (try to use good quality cable to reduce resistance - that would be the only problem). Other safer option would be to connect another data acquisition device to the PC so that CQC can read the temp from directly. A one-wire interface looks like it would work.
What about taking this opportunity to get a wireless weather station with an additional temp sensor for the pool? I'm using an Oregon Scientific unit I purchased last year and it has been working very well, and I'm not a big wireless fan.

I'm not sure whether your current system could take a serial-interfaced weather station and read data from it, however. You may need some other type of HA software system to do so. However, the weather station has a display panel that you could put in a location inside for her - it doesn't have to be tied to your touchscreen.

When I had my home in FL with the pool out back, I used a wired 1-wire sensor that I epoxied into a small tube on the end of some cat5 cable and placed about 3' down the side of the pool itself. This allowed me to get great, accurate readings of the pool water temp, and was still working fine when I moved, some 3 years later. If you place the sensor in the piping or a skimmer, you may not get accurate temps when the pump is off.
I'm using a Dallas DS1820 1 wire temperature sensor thats mounted in a 3/8" copper tube that protrudes slightly in the water flow (tube is closed at that end). I put a dishwasher-drain-like tee between the the skimmer and the pump and the tee portion has a 3/8" inside diameter going into a 1.5" main line. This works very well. I have a Peter Anderson 1 wire kit that's reading the temperature and feeding it to my HA system through a file on my server. It ends up in the Ocelot as a variable that can them be displayed on TV, PDA, etc.