Temperature Compensation

[Orcrone]

I know the temp probe is not supposed to need calibration. However my temp probe was about 2 degrees F. off from my Hannah tester and my Ranco Controller. Since those two agreed I decided to calibrated the Apex probe, but have no way to know which is correct. Since I use the Apex's seasonal temp settings two degrees is more than I want to be off either now or the peak of summer. After reading the unofficial guide I see mention of an NIST temp probe & I'm tempted to get it. Has anyone done this? Would you recommend it?

 

[aquamanic]

have no way to know which is correct

This is the problem with temp probe calibration. There's no fluid or calibration solution you can purchase to do this. The ONLY way you can know for sure is to calibrate/compare against a thermometer that is NIST certified. These are not cheap but are available with a little searching. Anything short of that and you're doing nothing but guessing.

If you know someone in the HVAC business, they may have access to one. An engineering company may also. College labs might be another place. Ask around your reef club. Think about places that routinely require accurate temperature measurements. Somebody will know someone that has access to one.

To be fair, I think it's less important that you know the EXACT temperature than it is that your temp probe is stable. If it's always off by 2 degrees you can deal with that as long as it doesn't deviate from that variance.

 

[Orcrone]

I'm probably causing my own problems. If I just set my temp at 77 and left it there I'm sure it would be fine as long as it was consistant. It wouldn't matter if the actual temp was 75 or 79.

Maybe because I like electronic toys I use the Apex's seasonal temp control. That will allow the temp to go as low as 75 in the winter & as high as 80.5 in the summer. If I'm off by two degrees I could potentially be setting the winter temp to 73 or the summer temp to 82.5. Not horrible, but at the edge of the acceptable range.

But like I said, I could just hold it at 77 degrees.

PS Just found your Unofficial Apex Guide. It's fantastic. Couldn't have done the firmware update (and many other things) without it.

 

[aquamanic]

You can still use the seasonal feature and have your probe off by 2 degrees. Just add/subtract from the seasonal value 2 degrees. This is documented in the programming section of the User Guide. Many people use this feature because they want seasonal variations but don't agree with the values in the table. This lets you customize it to your environment.

 

[Orcrone]

You can still use the seasonal feature and have your probe off by 2 degrees. Just add/subtract from the seasonal value 2 degrees. This is documented in the programming section of the User Guide. Many people use this feature because they want seasonal variations but don't agree with the values in the table. This lets you customize it to your environment.

Alan,

Thanks for the input. I've already adjusted the calibration of the probe by two degrees. I guess I'm just wondering whether I adjusted the calibration on the correct probe, or perhaps my handheld tester and controller are off.

 

[tmgrash]

Ice water is known to be 32deg f. In the food industry that is how thermometers are calibrated (on a daily basis). Fill a glass with ice, fill remaining with water, let sit for a min or so and then you have a known 32deg solution.

 

[aquamanic]

Those probes are not designed for those temps. I doubt you would get accurate results.

 

[tmgrash]

Ahh, dang. Thought I had some useful information. I figured thermometers were pretty standard across the temp range.

 

[aquamanic]

I figured thermometers were pretty standard across the temp range.

If you think about it, you wouldn't expect a meat thermometer to be able to read at freezing temperatures. I'm sure there are some types of scientific or industrial thermometers that have a range from freezing to boiling but I'm just as certain they go for beucoup dollars. In the case of these Pinpoint temperature probes, they're designed for a range of temps that are going to span maybe only 20 - 30 degrees before they lose their accuracy.