Need help re new thermocouple

[Dimal]

Great info gazza...

Probably worthwhile adding to the Documentation Sticky at the top of the page...

Mal.

[gazza]

There is some info on the Victor protocol here: Victor protocol - sigrok

Gary

[Rumo]

Mal thank you

I was wondering if anyone may have logged a sample serial session with this DMM by any chance? It's easy to do with a program like putty for example

Some basic instructions here: Putty- Hyper terminal | Chipkin Automation Systems

I'm looking to see if I can emulate the output on an Arduino.

Thanks a lot

[Dimal]

G'day MrJack...

It's more to do with how t/couples should be mounted and installed. Ideally, they should not be exposed to any kind of floating voltage that may occur as you can no doubt appreciate with the very small voltage levels being measured. Even though most inputs will have common mode induced voltage rejection circuitry employed, it may still be possible for a stray signal to interfere with the signal that you actually want.

Have you ensure that opportunities for possible ground loops have been identified and rectified? Is the t/c you're using a properly screened device? Where is the power currently sourced to power up the Controller? It is unusual for the kind of activity you describe to occur with a Controller that uses properly isolated inputs but, maybe the inputs are not so isolated.

If you're talking about powering up the Controller with a battery, how is this currently managed?

Mal.

[MrJack]

I have similar problems with my osPID. Touching the thermocouple bead to any grounded metal results in an input error.

I've often wondered if running the pid from a battery would make any difference.?

[Dimal]

I am browsing the forum looking for some details on datalogging. Does anyone happen to know what brand / model the CS DMM is or what chip it uses?

G'day mate...

Andy has these custom built to specification, so they will function as expected with the CS Roast Monitor S/ware. Even so, they still retain all of the usual DMM functions so can also be used as a general purpose unit...

Mal.

[Rumo]

I am browsing the forum looking for some details on datalogging. Does anyone happen to know what brand / model the CS DMM is or what chip it uses?

[Thundergod]

Re: Need help re new thermocouple

unless youre just talking about where it penetrates the roast chamber

I thought thats what he meant.

I do just that with my bead type probe to prevent the lead-in wire taking too much of a direct hit from any heat.

[Dimal]

Re: Need help re new thermocouple

Anyway, Im just going to insulate the probe with that woven fiberglass tubing stuff.

Youd be better off trying conductive silicone for this gc as the f/glass will insulate the probe to some extent, unless youre just talking about where it penetrates the roast chamber.... :-?

Mal.

[greencardigan]

Re: Need help re new thermocouple

Just to clarify, this is only happening when the thermocouple is conected to my custom roast controller (uses a Maxim 6675 chip the read temp from the thermocouple). It works ok in my multimeter.

Anyway, Im just going to insulate the probe with that woven fiberglass tubing stuff.

Thanks for the help.

[Dimal]

Re: Need help re new thermocouple

Many T/Cs and RTD devices are NOT isolated, in fact, most arent. The output from them is usually isolated at the input of the instrument being used.

Are they the yellow ones that used to come with the Digitech QM1538 multimeters?

The old type is but the newer model is a more robust design with the output cables fully shielded from the t/c fixing to within a couple of cms from the connectors. A much better t/c in my opinion...

The only way youre going to know for sure whats going on mate is to try another known good t/c with your meter and see how that goes. Were all wasting our time until you can do this....

Mal.

[hazbean]

Re: Need help re new thermocouple

No problem. Cant think why youre having this problem. I do have an old t/c which is yellow (it may be the one that came with the QM1538, which is now serving as an oven thermometer with the yellow t/c) -- I measured that also and found it electrically isolated.

[greencardigan]

Re: Need help re new thermocouple

I did test the beanbay t/s, both of them, see reply #2 (half an hour after your post).

They arent yellow. Im fairly sure they are different from what came with the Digitech, but I have had several and cant remember where each of them came from.

Sorry, didnt realise you checked both. Thanks.

[hazbean]

Re: Need help re new thermocouple

I did test the beanbay t/s, both of them, see reply #2 (half an hour after your post).

They arent yellow. Im fairly sure they are different from what came with the Digitech, but I have had several and cant remember where each of them came from.

[greencardigan]

Re: Need help re new thermocouple

Nope, my problem still occurs even if I dont have the popper connected. And even when powered from a battery rather than the mains.

Could someone test the beanbay thermocouples?

Are they the yellow ones that used to come with the Digitech QM1538 multimeters? http://beanbay.coffeesnobs.com.au/ViewProduct.aspx/322-spare-thermocouple-probe