calibrating temp

[hareball]

hi all,

what do you guys use/reccomend as far as calibrating your fishfinders water temp? any type of specific thermometer better than others for this?

thanks

[IrishAyes]

Hareball,
 I have never calibrated the temp on my finder.  If it is off, I suppose it can't be off by much.  I am more interested in any temp change as opposed to the actual temp.
  I figure, I am going to fish no matter what the temp gauge says.  And the temp reading you get from the finder is only surface temp anyway, most of the fish I go for are on the bottom where the temp will vary from the surface.  My opinion anyway.  Although lame it may be.   

[Reel Time]

 i would think any old thermometer would do the trick.

i was thinking my temp gauge was funky, reading 129 at times. belive i got it figured out to its picking up exhaust water being backdrafted to the stern at slow speeds. on the move its fine. still nice to have though as irish said, to find the temp breaks. although for inshore purposes i dont think its really all that relevant.

[CapBob]

Never specifically calibrated the Temp, but every two weeks or so I rest the machine to factory setting using the internal testing

[hareball]

thanks guys!

wanted to start logging in all details on trips and wanted to get the temp as close to true as possible. was thinking about one of those ones people throw in a pool.

[Capt. Ed]

Hi Hareball,

It has no meaning to calibrate the temperature. The circuitry to read and display temperature is pretty accurate. Maybe not precise but accurate. On the other hand, there is a calibration that you can add or subtract on depth finders that display speed. Everyone knows those spinning wheels kinda work but not really. The idea of calibrating the speed would be to use a GPS and see how "off" the spinning wheel is. The problem with that is that the error factor is not uniform (it varies as the speed increases) usually, so your calibration or "compensation" factor is off as well.

Temp guages do their job. They tell a reasonably precise temp of 2-3 ft. under the surface. What is more interesting is what Joe said, changes in the temp. We had a 10 degree F drop from 32 ft. of water to 18 ft. of water the other day. Weird but true and told us that if we worked on side of that temp break, we would catch. And we did.

If you are going to invest in a thermometer, get a submersion thermometer to measure temp on the bottom or use to find the thermoclines. Thermoclines are important to find in the offshore fishing (sharks, tuna, etc.) that you are planning to target.

Good luck,

Ed

[ped579]

Just a dumb question and observation.  In the specs. what will the temp. gauge go up to.  The reason for the question is that most gauges are calibrated to a known constant temp. the boiling point, 212deg at sea level, or the resistance equivalent.

Just my head working overtime...

Paul

[Capt. Ed]

Hi Paul,

I say this as a generalization ... no one in the software business will officially talk about their algorithms or how to interpret the codes coming from the hardware sensors. They will publish specs. for ranges. Garmin states:

5ºF to 158ºF (-15ºC to 70ºC)

for most of their units.

If I see somthing that does not violate an NDA I will post it.

Ed

[hareball]

thanks capt ed! I figured these electronics were as close to true as they could be but wanted to be sure

i've been thinking about something that could handle a few atmospheres of pressure to get temps in the deep. i've always had a little science in me especially with being in the aquarium hobby and would like to start logging in things like water temps and depth and also salinity levels of certain fishing hotspots and monitor the locations over the fishing season.

[Capt. Ed]

Hi Hareball,

Any dive shop sells them ... You just have to fashion a rig to send them down.

Here is a link to a primer that is industry neutral for anyone interested in the science concerning temperature sensors. The exact application is not spoken of between vendors.

The link is:

http://www.watlow.com/literature/prodtechinfo/files/sensors/corwe40205.pdf

The text is pretty good and not too nerdy.

BTW, internal temperature sensors are considered calibrated out of the box. Not to many people even discuss the type of sensor used in their products (competitive issues).

Thanks,

Ed

[hareball]

thanks capt

[ped579]

Hi Guys,

I remember reading some where about thermocouples and their resistance value.  I bet with a good dvom you get a range some where from 300ohms to 20,000ohms  for the range of temps listed under Garmins specs. I also believe they either use 32 deg F (0 deg C) or 212 deg F (100 deg C).  Being their specs do not go up that high it is probably 32 deg F.

Again just my head working over time.

Paul

[hareball]

 

[Capt. Ed]

Hi Paul,

Sounds like a good explanantion to me.

Don't let that head explode ... I need more pictures (LOL)!

Ed

[ped579]

SMILE

[Capt. Ed]

Hi Paul,

It looks like in 1990 that a new ITS temperature scale was introduced and they used the triple point of water instead of the freezing point of water. It also caused a unit, degree Kelvin, to be changed to just Kelvin due to a discrepancy introduced from between the 1968 and 1990 standard.

Yes, there is an "official" temperature scale. It's based on the true, thermodynamic temperature scale, but the real, working temperature scale is something practical which can be repeatably produced anywhere in the world given the correct practices and equipment. This is a lot like the freezing and boiling points of water but developed and refined to a higher degree (pardon the pun).

It is revised periodically as our technical abilities improve and as those who specialize in the field of metrology (measurement science) are able to come to some consensus.

This is the scale which the national labs, or those affiliated to those labs, refer to in the calibration certificates of reference devices that may be used in corporate or university or other measurement laboratories which provide a more local service such as to working instruments in a process plant or experimental apparatus.

A good link is http://www.temperature.com.

Ed

[ped579]

I think I've had it for to night.

I found something in the educational section of that web site where they talk about Bernulli's theory dealing with fluids.  Maybe use the venturi effect to make a non electrical bailing device ie; a bilge syphon.

Oh here I go again...

Good night.

Paul

[IrishAyes]

With all this scientific talk I just want to put across my theory. 

SHUT UP AND FISH!!!   HEHEHE.

[ped579]

YES SIR!!!

[hareball]

hahaha!!  *removes lab coat and grabs slickers*