Will this LCD temp display work w/phase change?

[xenolith]

I'm not looking for a controller, just something very simple to display the evap temp of my newly acquired Mach I. I really don't want to shell out more big bucks for a high quality digital thermometer. Plus, those things won't add anything to pimp out my rig either. :p:

Will this CompuNurse LCD (http://www.bestbyteinc.com/prodinfo.asp?number=SEN-CNU-001) work? I'm not crazy about accuracy, as long as it's within +/- 5C I'll be happy.

Or this nice backlit CompuNurse LCD (http://www.jab-tech.com/customer/product.php?productid=2642&partner=froog) version would be great.

If not, any input as to what can work would be awesome. Heck, I'm willing to spend more for a high quality LCD temp display (not a controller) like on a VapoChill w/ k-type probes, but I can't find any.

::::I just know I'm probably going to rile some of you aficionados here::::

[saratoga]

It says -40C, but I'd be skeptical. I've built meters using similar thermistor probes. They're actually quite accurate if you calibrate them, but the accurate range is fairly narrow before accuracy really starts to drop off. Once you get towards the edges, sensitivity drops off exponetially and readings start to become worthless.

Then again, for 7 bucks you could try it and see. Worst case you can use it to watch your condensor temps.

[xenolith]

Sorry for the noobness, but what would be a good condensor temp?

[eshbach]

at $8.28 after shipping i just bought one to see for ya :)

[BB mods's]

Sorry for the noobness, but what would be a good condensor temp?


Ya meen evap temp? "good" to me is sub 40*c and better.

[xenolith]

at $8.28 after shipping i just bought one to see for ya :)

:rofl: Thanks. I just ordered the backlit one... it'll be fun to play with if anything.

I guess I'm just frustraded there's no high quality graphical LCD displays available for phase change users.

[illmatik]

It says -40C, but I'd be skeptical. I've built meters using similar thermistor probes. They're actually quite accurate if you calibrate them, but the accurate range is fairly narrow before accuracy really starts to drop off. Once you get towards the edges, sensitivity drops off exponetially and readings start to become worthless.

Then again, for 7 bucks you could try it and see. Worst case you can use it to watch your condensor temps.

What's the best way to calibrate these types of 'budget/hobbyist' probes we get on devices like these so that we have an idea of its bias? I was also looking at these compunurses also as I think compusa is relabeling now (at least it looks an awful lot like one) Could I use something like a cup of ice water where I know theres a limitation to how cold it could be?

When I get the chance to start working on my first homebuilt unit, I'll invest in a uei or fluke meter. What would be the best thing to get for $40-$50 in the meantime to use as a more accurate point of reference, or is it wiser to save the $50 and put it towards a real deal thermometer and thermocouples. Which are the best thermocouples to use, are they K type?

[xenolith]

Ya meen evap temp? "good" to me is sub 40*c and better.

I know, 40C or better would be "good" for the evap.

But saratoga said they could be used to watch condensor temps... I was just wondering what would be good condensor temps?

[xenolith]

What's the best way to calibrate these types of 'budget/hobbyist' probes we get on devices like these so that we have an idea of its bias? I was also looking at these compunurses also as I think compusa is relabeling now (at least it looks an awful lot like one) Could I use something like a cup of ice water where I know theres a limitation to how cold it could be?

When I get the chance to start working on my first homebuilt unit, I'll invest in a uei or fluke meter. What would be the best thing to get for $40-$50 in the meantime to use as a more accurate point of reference, or is it wiser to save the $50 and put it towards a real deal thermometer and thermocouples. Which are the best thermocouples to use, are they K type?

I've read here the t- type thermocouple is the most accurate, but more expensive. K-types are good too.

[s7e9h3n]

What's the best way to calibrate these types of 'budget/hobbyist' probes we get on devices like these so that we have an idea of its bias? I was also looking at these compunurses also as I think compusa is relabeling now (at least it looks an awful lot like one) Could I use something like a cup of ice water where I know theres a limitation to how cold it could be?

When I get the chance to start working on my first homebuilt unit, I'll invest in a uei or fluke meter. What would be the best thing to get for $40-$50 in the meantime to use as a more accurate point of reference, or is it wiser to save the $50 and put it towards a real deal thermometer and thermocouples. Which are the best thermocouples to use, are they K type?
Ummm- a cup of ice water will be @ 0 deg C coldest = the freezing temp of water :p:

[saratoga]

What's the best way to calibrate these types of 'budget/hobbyist' probes we get on devices like these so that we have an idea of its bias? I was also looking at these compunurses also as I think compusa is relabeling now (at least it looks an awful lot like one) Could I use something like a cup of ice water where I know theres a limitation to how cold it could be?

When I get the chance to start working on my first homebuilt unit, I'll invest in a uei or fluke meter. What would be the best thing to get for $40-$50 in the meantime to use as a more accurate point of reference, or is it wiser to save the $50 and put it towards a real deal thermometer and thermocouples. Which are the best thermocouples to use, are they K type?

You probably can't calibrate something like this. Best you could do would be to put extra series or parallel resistance on the probe which would shift the it's calibration curb up or down, but not change the shape of it. I guess it might help a little, but its not worth it IMO. In my case, I was using a homemade meter, so I just changed the equation that the computer used to look up the temps from the voltage readings.

About thermocouples, T type are best, with K being fairly good as well. RTDs are better then either. Your best bet for this sort of thing is to look on ebay. You can sometimes get used lab equipment for cheap. If you don't require portability and can deal with a desktop meter, then you can sometimes get flukes for 20 or 30 bucks. RTD meters seldom go for that cheap though since they're much less common.

[illmatik]

Thanks for the info! Yeah, I'll probably hold out for something like the uei dt-200 used or overstocked somewhere, they seem to be reasonably priced (theres one on ebay now going for $122 w/ a pair of fluke K thermocouples) or even the dto-150 which seems to run around $75-$80. I have little to zero shelf or tabletop space left and would prefer something battery powered that can fit in the toolbox.

[s7e9h3n]

Thanks for the info! Yeah, I'll probably hold out for something like the uei dt-200 used or overstocked somewhere, they seem to be reasonably priced (theres one on ebay now going for $122 w/ a pair of fluke K thermocouples) or even the dto-150 which seems to run around $75-$80. I have little to zero shelf or tabletop space left and would prefer something battery powered that can fit in the toolbox.
No, don't get that one, I've noticed it before and there's a reason why it's been available for so long -
http://www.virtual-scientific.com/Catalog/products/instruments/temperature_humidity.html
This place used to have it cheaper, but it still sounds reasonable. Don't know their repotation though.....

[illmatik]

Awesome!! That instek multimeter add-on would be a sweet addition to my Fluke DMM, but I'm hoping I'll need to be measuring lower than -50C ;)

Who's got the best price on T Type thermocouples?

Also back to the thread topic, are there any digital displays (like the silver drive bay compunurse) out there that report moderately accurate subzero temps? I suppose it's easy enough to fabricate one, but I'm being worked hard this summer and would like to use that time for hittin the beach while it's nice out.

[s7e9h3n]

Awesome!! That instek multimeter add-on would be a sweet addition to my Fluke DMM, but I'm hoping I'll need to be measuring lower than -50C ;)

Who's got the best price on T Type thermocouples?

Also back to the thread topic, are there any digital displays (like the silver drive bay compunurse) out there that report moderately accurate subzero temps? I suppose it's easy enough to fabricate one, but I'm being worked hard this summer and would like to use that time for hittin the beach while it's nice out.
Dunno about T-thermocouples, but K's are usually fine for most users. If you're looking for a display, check out the thread here about "G-Frosters" and also PCIce had said something about a V.I.S. display which reads off of the mobo like MotherBoardMonitor (I guess that'll only work if you have a mobo which can read below 0).

[illmatik]

Yeah, that froster looks nice. I actually saw a very compact temp reader that reads K thermocouples. Its in a rugged yellow plastic type case which could be gutted and probably could sit behind a 5.25 bay panel. I gotta dig up that link.. I need to be hitting ctrl-d more often ;)

[xenolith]

Dunno about T-thermocouples, but K's are usually fine for most users. If you're looking for a display, check out the thread here about "G-Frosters" and also PCIce had said something about a V.I.S. display which reads off of the mobo like MotherBoardMonitor (I guess that'll only work if you have a mobo which can read below 0).

I noticed the G-Frosters too, but aren't they more a controller than just a LCD display?

That's what's so frustrating, they're no LCD displays available that provide accurate subzero temps without the added cost of a controller. Golden Eagle does make a mean custom controller though. ;)

[wdrzal]

I didn't see anyone answer the condensor temp question,if so I missed it. The lower your condensor temp the more capacity you will have, the closer to ambiant the better.Actully the colder the better, below ambiant is better .

[xenolith]

Ah, good to know. Thanks, wdrzal.

EDIT: But now that begs the question, where's the best place to put the thermistor?

[s7e9h3n]

Ah, good to know. Thanks, wdrzal.

EDIT: But now that begs the question, where's the best place to put the thermistor?
It all depends on which temp you want to know? The first place I put my probe is on or around the evap face...

[xenolith]

It all depends on which temp you want to know? The first place I put my probe is on or around the evap face...

Sorry, I meant if I wanted to know the temp of the condensor, I guess anywhere will do?