accuracy poll

I am OCD, and work with very accurate instruments and do a lot of calibration of equipment. This gives me a skewed idea of what accurate is, so the question is what do you call accurate for your instruments?

I'm lot pickier about thermometers than humidity gauges. 5-10% is good enough for humidity, but with eggs especially, I'm going to want some real control over temperature.

+/- 0.000001%

for rack temps ill take +/- 1 or 2, humidity 5-10. i cant find any reasonably priced thermostats or hygrometer to replace my acurites. and acurites have probes so it works good. if anybody finds something let me know

Do you mean accurate or precise. I use some instruments that are very precise, so I am overilling it abit. I typically think that humidity +/- 5% is fine, and temps for a room or rack are fine at +/- 1 degree. However, I like my incubator to be +/- .2 degrees, and therefore have bought a thermostat that is very precise. Testing the actual accuracy of our instruments would be difficult at best, due to the cost of certified termometers and hygrometers.

Just my .02,

Tim granted accurate and precise isn't that same but typically a very precise instrument is usually accurate as well unless some major error has come about. I have good very precise and accurate thermometer at work (RTD platinum traceable) and I know how bad the cheap ones are. Hygrometers are easy and sadly can be with in 2% with out spending much over 10$ and just a small investment in time, it really, in my opinion, isn't that critical (I did it anyway if it can be it should be right?). Thermometers are a whole different game, calibration is problematic at best, and accuracy is very costly. The best that can be expected from a cheap one is 2ºF +/- .

I am OCD and simply can't relax knowing the temp could be 88-92º and not knowing which. I could not imagine anyone accepting that kinda of a range. I kept bringing that up here and there but it was pointed out to me not everyone was afflicted with my special kind of crazy. I was actually curious what the range was for others.

For me I can live with 1ºF +/- in temps and 5% is fine for hygrometers, although I did check and calibrate mine so they are 1%. I bought Herpstats because of the accuracy or the probe and at 0.9ºF +/- I can live with it. I have little notes on a grab bag of cheap digital ones, -1.6, +1.9 , -2.9 do not trust... My IR gun is ok it is 1.1 low on the bench but they vary so much with surface it is hard to be sure at all.

I was just trying to see what was ok by the community and try to remember that my ok and your ok against joe keeper may not be even close.

Out of curiosity what T-stat do you use for your incubator?

Chris, Hygrometers are easy I'll post the ones I checked and ended up going with. Temps are well hard really hard. I have some LC ones that are good to 0.5º but they are impracticle to use. I use it as a control. A good digital is very costly the one work has was over 1600$ The best I have easy access to and affordable is the Herpstat, I think the helix is about the same. It sounds crazy to use a herpstat to measure temps but I do, the probes are good and mine the worst I have is off by 0.7ºF the rest are better the best is 0.1ºF they are vary. All are within the specs. (out of 15 probes)

We use a Helix 1500 watt system. They are not being made anymore, and are getting harder to find. However, Jeff at Helix, told me he is working on a new system to replace the old 1500 watt system.

p.s. Thanks for the reply. I was really trying to invoke some thought on the part of other members that might not be very familiar with the difference between Precise and Accurate. I know most people don't realize there is a difference.

I spoke to a electrical engineer yesterday about that very thing, his response was basically the accuracy comes from the probe and the precision the controller. He likened it to a mercury thermometer a cheap short thermometer is very accurate because mercury is very sensitive but the precision of the marking is poor and it is no longer correct. He backed up what I feel that typically industry uses a resistive sensor which simply is not very accurate the electronics behind it could be precise but are delivered faulty information or they can be averaging and not be precise but the probe is the first weak link. It is unlikely that a manufacturer would spend the extra cash for a thermal coupler and not back it be good electronics. At least that is what I understood I am not much of an electronic guy so I am a bit sketchy of the details I am just regurgitating what I was told.

Oh this is the hygrometer I have settled on. I bought ten and tested all ten and found them all to be with in 2% of correct. I adjusted them and yesterday after 3 months of use I checked 4 and they were still spot on. The magnet sucks I tossed it away and replaced it with a rare earth one that has been working much better (instrument inside magnet outside) The metal ring on the back came unglued on 6 of them I used hot melt to re attach it.

http://www.youtube.com/watch?v=1AMyVUx0Y60

It is around 9$ each. The digital one I also bought this a hygrometer it was also within 1% and is also quite good the temp is better than some but still is out the one I had was +1.3ºF The problem I had is the adjust dial on the front moves easily (I only bought one) and was reading very badly after the second night I have a feeling that my nosey male did his own adjustment (way off, it went from 66% to 9% over night). It has a sticky pad on the back that I stuck a metal washed to and used a magnet to hold it in place. I am using it in my snake room it works great I have thought about gluing the adjustment dial and trying it again but it is 20$ + shipping or 45$ local and I am happy with the brass one so I have not bothered trying.


http://www.shopwiki.com/_HygroSet-II...94390&s=206383

how can you tell if your instruments are giving you the right #'s you need?
i mean at some point, doesn't it just boil down to trusting what your device is telling you, knowing that it was designed to do just what it is supposed to do...whether it be a thermometer monitoring temps or a hygrometer monitoring humidity.
with every device we humans use we always end up having to just trust that the person or machine that made that device didnt screw up and hope that we got a device that is functioning to the best of it's ability.
i dont mean to throw a whole load of contradiction into the post but i'm really just curious.

That is actually what for me this is about every instrument has a manufactured tolerance. A range that the accuracy is supposed to be with in. The issue is most people don't pay any attention to that. For example the specs on my Accurite state that it will be with in 2ºF +/- of correct. So unless I have a better thermometer I have to accept its deviation. It could be correct spot on or it could be 2 degrees off. 88-92 if it is reading 90. No way of knowing unless you buy one that has finer tolerances. You can get digital ones that are 1º or 0.5º or 0.01º The price goes up monstrously as you get less possibility of error. A traceable one means before it left the factory it was placed on a calibration bench and tested that it was correct and it is certified by the manufacturer with a serial number and the records of that test.

Does this help some?

To be honest I just don't worry about it. As long as my snakes are healthy and thriving it's accurate enough for me. :gj:

Quote:

---

Originally Posted by kitedemon

I spoke to a electrical engineer yesterday about that very thing, his response was basically the accuracy comes from the probe and the precision the controller.

---

Unless you're like me and cheat by using a sensor in the probe that is a controller. :^) The sensors in the Herpstat probe are digital. They feed back a data stream with the temperature info and my thermostat designs just read that data.

The most common thermometer sensors (thermistors) are resistor based and as the temperature change their resistance changes. Simple huh? Except you are connecting that resistor to a cable so now you add the resistance of the cable. Then you couple that to several other components inside a controller which also usually have 2-5% tolerances and often all of that is affected by the quality of the power regulation the unit is running. So to an extent every circuit could have a different reading. For me there were just too many variables that could affect the true temperature with this setup so I went digital.

Before we ship any of our probes they are plugged into a Herpstat Pro unit four at a time and they all have to be within a degree to pass the test. Usually they are less than half a degree difference. The stated accuracy from the manufacturer of the sensor is +- .9 degrees but in our testing they are even closer.

One thing I want to point out is alot people cause themselves problems by using aluminum tape to secure a probe. Aluminum is a good conducter of temperature but it can pull heat away from the probe as well acting as a heatsink. Any other non-metallic tape is better. :)

Dion Brewington
Owner, Spyder Robotics

I stopped using humidity gauges over 6 months ago because they were so inaccurate.

Dion,
I actually trust the herpstat probes over everything. I have always found them to be very accurate. I use it against the others the empty probe slots I have I use for checking temps.

Spitzu should I tell you I went through 14 different guages before I settled on the ones I use now? I hear what you are saying there. The silly things are the worst ever, the current ones I have so far have not wandered much but at least I can change them when they are wrong rather than tossing them out.