Using a digital thermometer

[EDG]

The local Harbor Freight has a $39.99 digital Volt-ohm meter marked down to
$19.99. This meter comes with a type K thermocouple and can read up to 1000° C besides all of the other VOM functions. Have any of you bullet masters ever used one of these? They are so cheap that you could buy several for use in the pot, attached to you mold blocks and attached to a second pot or mold heater. I am going to pick one up tomorrow and test it this week end. My goal is document the temperatures that I get best results with and record the data for future use.
Any comments?

[crazy mark]

EDG,
I use a meter that is a little more expensive. You can buy spare thermocouples fairly cheap so you have several. You can drill a small hole in a mould to stick the end of the thermocouple in. The HF's are fairly accurate but don't hold up to being dropped too well. I have several of the HF meters with-out temperature and they work fine for home use. Mark

[Newboy]

I used a thermocouple on my Fluke meter. It is accurate to about a half a degree. I only used it to calibrate the settings on my pot, and then I don't use it any more.

[Willbird]

So the meter has a special range setting to use a type K thermocouple ??


Bill

[crazy mark]

so to speak yes. It also has a female plug for the thermocouple.

[Willbird]

So what signal does the thermocouple send ?? voltage, ??

IE can I just buy the thermocouple and use my own volt/ohm meter and a conversion chart ??

or is it just simpler to buy the whole HF setup ??


Bill

[crazy mark]

The HF one has the scale built in and a position for temp. The one I have uses the 2MV DC and 2VDC settings for the temp range as I have a plug in adapter. Easier to just buy the HF model.

[Willbird]

I did some surfing Mark, meaning I tried first hehe.

Do you have a source for the thermocouples so if I buy the HF model I can get more thermocouples ??


Bill

[castalott]

Digital thermometers are the way to go...

I have an industrial unit on my homemade casting machine. You will be surprised how much the lead temp. changes. I would like to add another for the mold blocks. I would like more information on this part.

Thanks, Dale

[Newboy]

The thermocouples read out in millivolts. Fluke has a fancy adapter you plug into your meter to convert the reading into temp. You could do your own conversion, but you would have to take some readings with a thermometer to get it calibrated.

A thermocouple is just a junction of two dissimilar metals. K-type uses certain alloys. Different type for different temperature ranges.

You could buy the thermocouple wire, and melt the ends of the two wires together, or you can buy a pre-made unit for more money (they are cheap, though).

[Gussy]

I have read the flier over and over. It says "includes temperature probe function" but does not say the probe is included. Is it??
Gus

[crazy mark]

mcmaster-carr.com. thermocouple probes. They have various ones for different temp ranges and applications.

[EDG]

I have read the flier over and over. It says "includes temperature probe function" but does not say the probe is included. Is it??
Gus

The store display meter and one of the boxes I looked into have a single thermocouple included with the test leads. I had a busy week so I didn't make it by there but I will get one tomorrow. The Harbor freight site has a link to the user's manual. It appears it is accurate to 1% up to 700°C.

http://www.harborfreight.com/cpi/taf...m&ItemID=37772

I can't this to open tonight. but it has a list of included accessories on page 23.

[EDG]

I got the meter today. The 37772 came with a type K thermocouple in the package. It reads out in C° (centigrade degrees). Response time seems to be about 30 seconds. That is it jumped from room temp 27° to 33° (between finger and thumb. in about 30 seconds. I will try it out tomorrow. As I was driving to the store it occurred to me that I could buy addition thermocouples and use this meter to calibrate my other meters. I have an old Rat Shack analog meter and a chumpy digital I got from Sears. For those out there conspiring to get an additional meter, Harbor Freight has a small meter on sale now for $3.99.

[Willbird]

http://www.omega.com/ppt/pptsc.asp?r...NTS&Nav=tema02

there are some, I looked, and looked, and looked, and finally asked on subguns.com and bingo, there they are

[Willbird]

EDG, are you sure it is a 37773 ??? the link you posted was for the 37772 and the 37773 I looked at did not come with a tcouple, it looked like it had a place to plug one in tho. and it's retail was 10.00 less than the 37772 that they were out of

Bill

[Willbird]

I got a 37772 today at Harbor Freight, it does indeed have the Thermocouple, the 37773 did not.

Bill

[Willbird]

I set the meter up and checked some boiling water, it told me 96c, according to this webpage water should boil at my house at 98.5c (dunno if the salt from my softener changes boil point or not)

http://www.csgnetwork.com/h2oboilcalc.html

then I put the tcouple in the molten metal in my rcbs promelt set at 850 after it ran a couple cycles and I presume settled down. The meter told me 446c which converts to 834.8 degrees.

The tcouple bead did not seem to tin badly with the boolit alloy, I wuped it clean while hot readily.

Bill

[grumble]

Bill, according to my precision turboencabulator, the error on your temp probe isn't too far off. Looks like about 2.4% for the boiling water and 1.8% for the melted lead. Assuming of course, that the temperatures you were using for a "standard" were correct.

For our purposes, I'd think that repeatability would be more important than exactness. That is, if you get the best casting results at 420*C, it really wouldn't matter if the actual temperature was 426*C or 415*C, all that would matter is that a reading of 420* would still be the same temp the next time you sit down to cast.

It may well be that the thermocouple was calibrated at the top end of its range, say 900*, and that the error tolerance increases the farther down the scale it goes.

Sounds like a neat item to have, anyway!

[EDG]

[QUOTE=Willbird]I set the meter up and checked some boiling water, it told me 96c, according to this webpage water should boil at my house at 98.5c (dunno if the salt from my softener changes boil point or not)

At 910 ft elevation and 29.92 IN/HG the boiling point should be 98.7C°.
My meter showed 96C°.
I found another meter with a thermocouple at another site for $8.99. Trouble is they are out of stock.

EDG