In-line thermometer

[holmburgers]

Hey y'all,

So I'm redoing my darkroom, and so far everything is much improved. I'm setting it up in my laundry room and I'm using the W/D hookups to do so. This is a great way to setup a darkroom w/o needing dedicated water hookups. I'd be glad to discuss how, and it's quite easy with the right plumbing.

Anyways, I'm hoping to get a little fancier this time around and I'd love to include an in-line thermometer.

I'm not opposed to spending $30 or so and getting a new one, but I'd rather explore the DIY possibilities first.

Here is one idea from the brewing circles, and although it wouldn't be dreadfully accurate, it'd probably be good enough for non-critical black & white work.

http://www.forrestwhitesides.com/node/44

And here is a more taylor-made solution, but it uses the same mechanism (those stick-on thermometers from the pet store)

http://www.breworganic.com/thrumometerin-linethermometer.aspx

Anyways, I think that with our powers combined, we could develop a more sophisticated and affordable solution.

Cheers!

 

[Bob-D659]

Drill hole in faucet spout, insert one of these $6 specials, secure with some sort of glue. They work like a charm.

http://www.harborfreight.com/instant-read-digital-thermometer-95382.html

 

[holmburgers]

That's certainly a thought that I had. And luckily I have a rubber tube for my last stretch, so it'd be as easy as an ice-pick and some super glue probably.

However, I just came across these.... which would be a fairly elegant solution.

http://www.allproducts.com/manufacture100/cotronic/product5.html

These are going for fire-sale prices on eBay. The only concern is +/-1°C from 22-50° and +/-2° outside of that range. However, once the "slop" was established, it'd be pretty reliable.

Hmm, maybe not such a brain buster afterall...

 

[domaz]

Or you could put in a T-Joint, get an End-cap drill a hole in it large enough to accomodate a dial thermometer and glue it in. It would be hard to make one that didn't leak though.

 

[Mike Wilde]

As long as there is not a lot of downline back pressure, I have just taken a dial thermometer and inserted it in the almost horizontal section of the facuet head that to downstrem of the two valves.

I wrapped the junction where the stem of the thermometer goes into the faucet line with tape to cut down on the leaks.

I use self amalagamating electrical insulating tape.

The nice side effect of this connection is that you are able to twist the whole thing.

I usually twist it so that the water flow I am looking to acheive points the indicator needle straight up.

Thne a glance, without reading the dial calibrations tells you what adjustment is needed.

 

[bobwysiwyg]

These alt. methods re: drilling holes and gluing give me the willies. I hope none ever fail while you're on vacation.

 

[holmburgers]

These alt. methods re: drilling holes and gluing give me the willies. I hope none ever fail while you're on vacation.

I agree, and that's why any modification I make will be after the main on/off valve

 

[Paul VanAudenhove]

Seems to me I saw a neat DIY version using a T and a dial thermometer someplace. The length of the pipe was sized to the length of the dial thermometer probe. If I recall it correctly, the end used a washer fitting with a rubber cork that the thermometer went through. Then, it was screwed in place by another washer fitting, holding the stopper in. It didn't look like it would leak.

 

[holmburgers]

Paul, I'm having trouble visualizing exactly how the cork was screwed in place, but I can kinda imagine it and it sounds very good.

Are you a good artist, can you draw a picture?

Something like this sounds very robust indeed..

 

[Mark Fisher]

I'm doing a similar thing. I had a used mixing valve that went bad so now I'm getting a new one from a plumbing supply store. After the mixer and shut off, I'm thinking of running an tee joint somewhere after the shutoff and getting a thermometer with NPT thread on it (just bought one on ebay for $20), This way I can plug in the thermometer into one of the legs of the tee and just run the water out the other leg.

 

[Bob-D659]

When I said drill a hole in the spout, there is no pressure in a faucet spout when the taps are tuned off.

 

[jeroldharter]

Temperature is an important variable. The example shown measures in 4 degree F increments which is pretty coarse. I would not cut corners on measuring temperature.

 

[holmburgers]

Temperature is an important variable. The example shown measures in 4 degree F increments which is pretty coarse. I would not cut corners on measuring temperature.

I agree that the first link with the pet tank thermometer is not a good idea.

And check this out; it's pretty cheap... (search "threaded thermometer")
http://www.houseneeds.com/shop/HeatingProducts/HydronicHeating/gauges/temperaturegaugebuypage.asp

 

[clayne]

Automotive water temp gauge with NPT threads. 1/4 copper tee, some assorted adaptors, and you're done.

 

[Paul VanAudenhove]

There is a Delta One version avaiable at Calumet:
http://www.calumetphoto.com/item/DT2021/

I'm certain you could make something simpler than that using a T to allow access for the thermometer.

 

[holmburgers]

clayne, that sounds like a good bet except that most automotive gauges I have seen don't go low enough.

The Delta one on Calumet is of course a beauty, but as with most darkroom gear, it's function doesn't justify its price.

 

[bsdunek]

McMaster has dial thermometers with standard plumbing threads on the back side. They list one for kitchen use for $35 with threads and a range of 0-200°F and an accuracy of ±1°. That may work.

Another was is with a tubing compression fitting. Solder that on the tee, put the thermometer stem through and tighten the nut. That's how mine works.
What bothers me is a darkroom in the laundry room. In my experience, laundry rooms are full of lint. I would never have a darkroom anywhere near one. Just IMHO.

 

[holmburgers]

What bothers me is a darkroom in the laundry room. In my experience, laundry rooms are full of lint. I would never have a darkroom anywhere near one. Just IMHO.

You are absolutely right. But it's either this darkroom or NO DARKROOM....

 

[Mike Wilde]

Mine is next to the laundry. I ask all that empty the dryer lint screen to gently pull it from the dryer, lay it gently on the dryer, and then mist it with a little water pump spray bottle we keep on a shelf above the machine. That turns the lint into a damp mat. the screen goes back into the dryer, and the top of the dryer gets wiped with this soggy bit of lint, before it goes in the trash bin.

The concrete floor is also painted, and I periodicaly vaccuum the laundry room floor, and around the appliances themselves whan vaccuuming the adjacent family room. This keeps the dust to acceptable levels.

I have a pair of small room air filters in the laundry and darkroom. I turn them on in the morning when I am going to print that night, particularly in the winter when the relative humidity is low.

 

[removed account4]

hi

i searched for 2 days to find the manufacturer of
the in line thermometer fixture that i have had since the 70s
it was made by a company called pfefer in van nuys california
and it also has the name "flo temp" on the side.
it is white plastic and you just put your lab thermometer in the side
there is a threaded hollow shaft that secures the thermometer
and a threaded 1/4" outflow on the base and it clamps on to the end of your gooseneck faucet ...
but ... i couldn't find the fixture, or anyone who sold anything similar
to it ....

i did find a 60$ in line thermometer just like another one i have
http://www.google.com/products/cata...ct=result&resnum=1&ved=0CFYQ8wIwAA#ps-sellers
you just put hose in 1 side and out the other.
the one i have worked ( works ) well and i never had trouble with it.

( i just googled in line thermometer on google to find it )

good luck !
john

 

[ic-racer]

hi

i searched for 2 days to find the manufacturer of
the in line thermometer fixture that i have had since the 70s
it was made by a company called pfefer in van nuys california
and it also has the name "flo temp" on the side.

I used a flo temp. B&H show it here but I don't think they sell it any more:
http://www.bhphotovideo.com/find/Product_Resources/darkroom/waterControls.jsp

 

[greybeard]

It's important to understand the difference between accuracy and precision; the first is the error with respect to some absolute standard, and the second is the measure of the smallest change that can be reliably detected. For darkroom work, and accuracy of 1 C (about 1.8 F) is overkill (other things will affect your process more than that) but a precision of 1C means that successive runs could differ by about 4 F without your being able to tell, and if this much variation is acceptable you probably don't really need a thermometer

That having been said, the tradeoff is usually between accuracy and precision at any given price point. Thermistor thermometers are wonderfully precise, but unstable and therefore not famously accurate; thermocouples are easily accurate enough, but a readout with 0.5 F precision is pricey. The best solution seems to be to use a precise (probably electronic) thermometer to gauge consistency, and check it frequently against an accurate, stable reference (for this, nothing beats an etched-stem glass thermometer, and the Kodak Process Thermometers were designed for exactly this purpose).

You should be able to find a dial-type thermometer built for pipe-tee installation in or near your price range, and a thermistor-probe type would be even better. But plan to back it up with a good reference thermometer.

Incidentally, dial-type thermometers are sensitive to distortion of the stems, since the measuring elements are inside them. Putting one into a compression fitting is an obvious, but not very good, idea.

 

[greybeard]

For what it is worth, this: http://www.thermoworks.com/products/low_cost/rt301wa.html would be ideal if it had a 1/8 inch stem instead of 2.5mm, so that you could just put it through a compression fitting. But there are even ways around that.

If you read the data sheet on the product above, you will see the instructions for recalibrating (which more or less confirms that it is a thermistor design) with a two-point calibration (boiling water and ice points). For darkroom work, a single-point calibration near your preferred process temperature (68 F, 75 F, or whatever) is much better, because the accuracy error is effectively reduced by the ratio of the thermometer span to the working range (180 F between ice and steam temperatures, divided by the 2 F or so that you really care about).

Having to tweak the zero point once in a while to make the device agree with your reference thermometer at working temperature is what happens when you pay $24 for a thermometer with 0.1 degree resolution

 

[holmburgers]

Good points greybeard. I have an excellent mercury-glass JOBO thermometer that would be reference quality, and if I had to check the in-line gauge only once a session, that would still be a boon. Assuming you could reliably know the inaccuracy of your thermometer, a gauge is a gauge.

A lot of good ideas and designs out there... I love plumbing.

 

[greybeard]

A bit more checking showed that there are quite a few thermometers of the style I mentioned that are listed as having 1/8" stems. They probably all use the same thermistor bridge/display driver IC, so the specifications (and prices) are all about the same. A pipe tee, a compression fitting, and you are in business.

The usual standard for recalibrating devices like this is every six months or so. For darkroom use, I would just run some water at the nominal temperature, check the glass thermometer, and note the display reading for the current session. When it gets off by a degree or two, get out the jeweler's screwdrivers and reset it.

The market for the cheap thermometers, by the way, is the restaurant/food service business; a "laboratory" thermometer with the same specifications is usually about 5-10 times more expensive, and a "medical" one is even more