Which one should I believe? (Herpstat vs. Temp Gun)

I recently received a Herpstat and decided to test it out on a spare sheet of Flexwatt.

Here's the problem:

http://farm6.static.flickr.com/5018/...c29be4017b.jpg
Untitled by jason.granger, on Flickr

The tempgun is 4-6 degrees off of what the thermostat is set to! Before you ask how I'm measuring the temps, here's how it's set up:

http://farm6.static.flickr.com/5296/...93c2791301.jpg
Untitled by jason.granger, on Flickr

As you can see, I'm measuring the temperature of the Flexwatt directly since it's not attached to a cage. Any ideas what's going on here? Is that tempgun just inaccurate?

OK, heres my thoughts on what I see. The probe is taped to the Flexwatt, but only a portion of the probe is actually making contact with the Flexwatt. The rest is being exposed to room temp air and the heat coming off the flexwatt. So the Herpstat is heating it up more to get the right temp. Take a piece of aluminium tape and cover the whole probe, that way the heat will be trapped all around the probe and you should get a closer reading.
Just my thoughts, correct me if I'm way off base here!

:confused: Bump I'd like to hear if anyone knows the solution too. IMO i feel that maybe its the herp stat as the probe is spherical. Thus leading to inaccurate readings as the ambient air cools the probe as its being heated by your flex what. This is just the chemistry major of me speaking, strike a hypothesis! But you could try to maybe put the flexx watt were you are going to use it keep it there let it heat and re-take the readings. Meaning don't move anything from were your actually going to use it and shoot the temps.

If they are still different you got me.

If you want fast results do a simple test. I am not sure if the herp stat probe is waterproof but grab a cup of warm water... shove the probe in... then shoot the water with the gun. see what you get!

But i feel its kind of hard to answer your question as its hard to pass the blame to either product.

Quote:

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Originally Posted by saber2th

OK, heres my thoughts on what I see. The probe is taped to the Flexwatt, but only a portion of the probe is actually making contact with the Flexwatt. The rest is being exposed to room temp air and the heat coming off the flexwatt. So the Herpstat is heating it up more to get the right temp. Take a piece of aluminium tape and cover the whole probe, that way the heat will be trapped all around the probe and you should get a closer reading.
Just my thoughts, correct me if I'm way off base here!

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My thoughts exactly your a faster typer then me =P!

Or just try putting the probe under the Flexwatt.

Is your temp gun consistent? If you zap the tape 10 times in different spots will it read the same temp or very close? I bought a infrared thermometer last week that is crap. It reads different everytime. My herpstat has always been spot on. But my probe is covered in foil tape too. I agree with the others, try covering the probe with foil tape but also try taking the average of your readings from the temp gun. If the range of the readings is kinda great, you may have a problem there. Herpstat is accepted as a great product - great choice!

Ir reflects and flexwatt is shiny this will lead to false readings. Most ir guns are calibrated to be looking at something roughly the colour and reflectance of a brown paper bag everything else is off somewhat. The allowable deviation of this ir gun is about 2ºF up or down (the PE1 is the best sub 200$ gun I have found at 1.5º +/-) So 5 degrees off is not a big surprise. The deviation on the herpstat probe is very low .3 I believe. IR guns are really not very accurate under the correct circumstances they can be ok. but that is it. Get a GOOD thermometer (mercury lab grade or platinum probe traceable digital but sit down when you look for a good (.5º accuracy digital one it will scare you. some LC ones are also very good and are cheap. Just check the packages on the shelf if ten or more read the same you can expect a .5 degree accuracy. To test this for your self flip the flexwatt over for an hour or so so the herpstat probe is on the carpet away from drafts and them quickly move it and check the carpet it should be with in 2 degrees. Don't take my word for it CHECK the SPECs and email Dion at spyder Robotics he will tell you the same thing.
Alex

Quote:

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Originally Posted by saber2th

OK, heres my thoughts on what I see. The probe is taped to the Flexwatt, but only a portion of the probe is actually making contact with the Flexwatt. The rest is being exposed to room temp air and the heat coming off the flexwatt. So the Herpstat is heating it up more to get the right temp. Take a piece of aluminium tape and cover the whole probe, that way the heat will be trapped all around the probe and you should get a closer reading.
Just my thoughts, correct me if I'm way off base here!

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I was told specifically not to use foil tape by the owner of the Herpstat site. He said to use clear packaging tape, which I didn't have, so I just used Scotch tape.

Quote:

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Originally Posted by Ladybugzcrunch

Is your temp gun consistent? If you zap the tape 10 times in different spots will it read the same temp or very close? I bought a infrared thermometer last week that is crap. It reads different everytime. My herpstat has always been spot on. But my probe is covered in foil tape too. I agree with the others, try covering the probe with foil tape but also try taking the average of your readings from the temp gun. If the range of the readings is kinda great, you may have a problem there. Herpstat is accepted as a great product - great choice!

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It is fairly consistent, depending on what I'm aiming at. If I aim it at my wall, it is within a one degree margin every time. Flexwatt, more like a two to three degree margin.

Quote:

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Originally Posted by kitedemon

Ir reflects and flexwatt is shiny this will lead to false readings. Most ir guns are calibrated to be looking at something roughly the colour and reflectance of a brown paper bag everything else is off somewhat. The allowable deviation of this ir gun is about 2ºF up or down (the PE1 is the best sub 200$ gun I have found at 1.5º +/-) So 5 degrees off is not a big surprise. The deviation on the herpstat probe is very low .3 I believe. IR guns are really not very accurate under the correct circumstances they can be ok. but that is it. Get a GOOD thermometer (mercury lab grade or platinum probe traceable digital but sit down when you look for a good (.5º accuracy digital one it will scare you. some LC ones are also very good and are cheap. Just check the packages on the shelf if ten or more read the same you can expect a .5 degree accuracy. To test this for your self flip the flexwatt over for an hour or so so the herpstat probe is on the carpet away from drafts and them quickly move it and check the carpet it should be with in 2 degrees. Don't take my word for it CHECK the SPECs and email Dion at spyder Robotics he will tell you the same thing.
Alex

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I've heard of temp guns reflecting off metal and giving inaccurate readings. Interesting.

You can't go by what the thermostat is set at. Sometimes you have to put them a couple degrees up or down from what you actually want. The important thing is to have the floor of the enclosure the temp you want. Measure this with a digital thermometer and see how close it is to your gun. My gun is only 1 degree difference from both my thermometers!

I'd be partial to the temp gun. They're incredibly accurate, and they will change from area to area depending on how far away you are and such. I've heard of themostats being off much more often than I am comfortable with, so just set the thermostat to whatever gives the correct reading for the temp gun

Quote:

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Originally Posted by Valentine Pirate

I'd be partial to the temp gun. They're incredibly accurate, and they will change from area to area depending on how far away you are and such. I've heard of themostats being off much more often than I am comfortable with, so just set the thermostat to whatever gives the correct reading for the temp gun

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Sorry, but this is naïve. 2 degrees up or down is not particularly accurate. For example if you read 92ºF it could be 90-94ºF The PE2 is better it is 1.8ºF, the Fluke ir guns are a tad bit better they make a model that is 1ºF up or down... but it is more than a BEL. READ THE SPECS!

http://images114.fotki.com/v652/phot...unspecs-vi.jpgHosted on Fotki

Flipping the Flexwatt upside down so that the probe was between the Flexwatt and the carpet worked. Now I'm getting better results with the temp gun. Thanks guys.

The difference you are seeing has more to do with the tool than the actual temperature.

A thermometer probe is designed to measure air temperature. A temp gun specifically measures surface temps. A temp gun doesn't measure air temps at all. It measures reflected surface temps, physical objects/surfaces.

Using a probe like that to measure surface temps is very difficult to do. You have to tape it down, bury it, all kinds of different tricks to get surface contact for a reasonably accurate measurement.

If the probe is water proof, you can submerge it and it will measure those temps just fine, because it is completely surrounded by the "surface". That doesn't help with heat tape setup, but it may help to understand the concept.

In a basking lizard setup, using a probe from either a thermostat or a digital thermometer- trying to take the surface temp of the basking spot is incredibly difficult, again because of the lack of contact for the probe. Using a temp gun, I can read the actual surface temp at 134F (or whatever it is). Using the probe, I may be able to only get it to read 127F. If you raise the probe off the surface, so it is measuring only the air temp, even 1/8" off the surface, the reading may go down 15-20 degrees. Air doesn't hold a temperature anywhere nearly as well as a physical object with thermal mass. That is why on an 80F degree day the asphalt might be 135F.

Surface and air temps are radically different. Use a probe to measure air temps, and a temp gun to measure surface temps. (there are specialty probes/tools that measure surface temps, but they don't come on thermos that we use for reptiles).

In the end, it is all ok, because it is all relevant.

Your temp target is the temperature that your reptile has access to. You want a 92F hotspot (or whatever). The setting on your thermostat is not so important, as long as the RESULT in the cage is 92F. Depending on probe placement, your thermo setting might be 92F, 85F, or 103F.

Your snake doesn't read the number on the thermo, it just searches for accessible and usable temps, so the setting doesn't matter. The result does.

A temp gun is incredibly accurate. If you are measuring surface temps, and for this application (heat tape to create a hot spot) you are, it is the most accurate tool you can have. Make sure the lens is clean and free of dust (use a q-tip to clean), you have a charged battery, and if the unit has adjustable Emissivity, it is set to 95E.

Also be sure you are measuring from an appropriate distance. A unit like the TG1/PE-1 has a 1:1 distance to spot ratio. At 1 inch you are measuring a 1 inch spot. At 6 inches you are measuring a 6 inch spot. You wouldn't want to take a reference measurement of 3 inch wide heat tape from 6 inches away, you would be measuring the heat tape PLUS the rest of the cage surface.

I typically use the TG1 unit at 2-3 inches away for hot spots, basking spots, etc.

Finally, if you want a reference, use the ice water bath test. Assuming a submersible thermo probe-

Get a Super Big Gulp sized cup. Fill it with crushed ice (crushed ice will give more accurate result compared to cubes). Fill with cold water. Use a spoon to slowly stir the water. Slowly. The liquid water will get right down to the freezing point at 32F. If you stir quickly, you create heat, stir slowly.

Submerge your probe in the water. Continue to stir, see how close you can get to 32F. Should be able to get within a degree. Salt content, altitude, there are a couple of factors that will change the absolute temp result, but you will get close.

Now take the surface temp of the water as you stir, from an inch away, with your temp gun. This method using the temp gun is INCREDIBLY accurate (clean lens, good battery, 95E).

If your thermostat is accurate, and it should be, you shouldn't see more than a tenth of a single degree difference between the two.

That is a simple test, and yields a terrific result. A boiling water test is NOT the same. Water boils at different temps (salt content, altitude) but more importantly a temp gun would be measuring the tiny droplets of water in the steam and not the bulk water itself. Just FYI.

In our setups at Pro Exotics, the setting on the thermo is RELEVANT to the cage hot spot temp. We check actual temp with the temp gun, and adjust the thermo up or down accordingly. Probe placement, heat tape, heat pad, substrate, air flow, they all affect the resulting hot spot, but these things are all related, and once you understand the nature of that relationship, it all becomes pretty straightforward and easy : )

As for the accuracy of the unit, it is spec'd at + or - 2 degrees. But that is the required spec. I find the units to be accurate within a tenth of a degree in actual use : )

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