I can't seem to get the pdf to open from where I am.  probably adobe reader is too old.  I'll try to check it out later and get back to you.

Hey, I'm back.   Sorry, funeral day today....


Anyway,   here's the boring bit.

   Thermocouples and PTDs work entirely differently.   A PTD is basically just a resistor, and just like all resistors, if it is warmed up it's resistance will decrease. On its own this is no use, but apply  some power across it and you get a varying voltage proportional to temperature.
A thermocouple requires no power, it actually generates a small voltage when the tip is heated.

The input of the PID measures the voltage and gives a reading of temperature, but due to the difference between a thermocouple and a RTD you can't just switch between one or the other.  The input circuit on the PID has to match the sensor.   Again, the K02 part of the model number says your PID is designed for a type K thermocouple....

Here's the important bit.

A thermocouple, because it generates it's own voltage like a battery, has to be connected the correct way around.  At room temp, when the TC and it's connecting wires are all at the same temp it gives 0V.  If the "cold compensation" is set correctly in the PID then it should read room temp.
As you heat the TC junction tip you get an increasing voltage on the connecting wires.  If the temp readout falls, the you have the TC connected in reverse.


PLEASE check the operating temp of that SSR.  It is designed to be mounted on a heat sink and you have it screwed to apiece of wood....

Is no one concerned that this is mounted in a wood box?  I'd be afraid of components heating up past the ignition point of wood.

mike_mccue


Karyn mentioned the fact that there is a need for a metal heat sink.

In general, if electronics could get hot enough to ignite wood our tube amps would have all caught fire a long time ago.

Switching power supplies however have a dramatic failure mode that doesn't go well with wood.

So, I agree, a metal box seems worthwhile.

Maybe one of these:

 

I see karyn's post now where she did mention it.  My tube amp has lots of ventillation and all components are mounted to metal.  This looks like a kitchen drawer.

Once again, I'm quite taken aback with all the expert help being given here - really appreciate it.

Yes, before I use the system properly I was planning to mount the SSR on a heatsink - it's current state is temporary, until I can get the thing to work!

Regarding polarity - that's what I thought, however I tried both combinations on both varieties of probe, and neither worked. On the K type, the 'correct' polarity yielded the 0000 error message, then when I reversed the polarity, it worked, only backwards as described earlier.

Karyn, it was my understanding that this particular PID can utilize several varieties of thermocouple, with options for configuration. Here is some additional documentation I found: http://seattlefoodgeek.com/wp-content/uploads/2010/02/CD-101-Instruction-Manul-including-PV-adjustment.pdf

http://mightyohm.com/wiki/resources:cd101

I have to do a very long mixing session today, so won't be able to have another tinker until tonight my time - I'll keep you posted, and I'll double check the wiring is as you say, Beagle, although there is no A or B labelling...

if they're not labelled then you have to figure out which ones are which.  with a combination of 3 then you could easily have gotten them mixed up.

do you have an Ohm-meter?  there will be very low resistance between the two "B" wires and some higher resistance between either of those B wires and the A wire.  I don't know what the resistance will be without studying the RTD better, but it will be less than 1 Ohm between B wires and something higher between B and A.

Mike - mmmm.  I LOVE sun tea!  I haven't had any in a LONG time!  gonna have to make some this spring/summer!

that sounds like a plan!!!!

it's possible the RTD is defective.  it's kind of hard to screw up an RTD, but it's possible - I guess the connections to the resistor network might be open or too high.

I don't think I'm being quite clear, so I'll try a different approach.

Plug your Les Paul in the 'inst' input of a Marshal and you get Rock.
Try and plug a LDC mic into the same input and you can sit on the floor re-wiring the plug all day long but you'll not get it to work.
Why?  I shouldn't have to say, but the input of a Marshall is just not built to accept a LDC mic.  Wrong input impedence, not balanced, no phantom power.


The K02 in the model number of that CD101,  as printed on the label, means the input is built to accept a type K thermocouple.  This is repeated on the label where is specifies input as "K" and range 0 - 400.
The electronics on the input will not work with a RTD.  For that to work you buy the model CD101 that has RTD inputs.

The processor inside is exactly the same for all the different models with different I/O options. It should be factory preset to match the input (K type TC).  Changing the input type setting does not magically make it accept a different temp sensor.

jamescollins


Understood! Thanks Karyn - maybe we should have been talking in Les Paul and mic terms from the start? 


I think the problem with the K type before arose from my cheap and horrible crimping tool. The wire on the thermocouple was too thin to get properly 'gripped' using the tool I had, so I doubled up the wire and it appeared to be OK. But when it still didn't work, I tripled the wire up, re-crimped, and all is well now.


I need to sort out that heatsink now - I'm thinking I can just buy one from an electronics store? Otherwise, will it suffice just screwing it to a piece of aluminium?  Probably not, I'm pretty sure they'll sell them at the store.


Thank you so much everyone, I'll post some pics of the fruits of my (our) labour. Rib eye steak this afternoon, then some pork which has been soaking in its brine for way too long!

First with the wire & crimping - most wires from thermocouples were not made or designed for crimping to a connector. Usually a direct screw connection.

Second as to a heat sink - sure a piece of aluminum will work but a regular heatsink will work better. And don't forget heatsink grease which acts as a coupler between the device to be cooled and the heatsink. You don't want a dry interface between the two, but at the same time this is one instance where more is not necessarily better. Apply some grease to the heatsink and then wipe most of it off just leaving a thin film. Some devices come with a piece of solid material that's supposed to act as a coupler between the device and heatsink - I still would use grease there between each surface.

chuckebaby


what did miss?..i open this page and see a canned ham and some iced tea.

You missed the picnic break.

mike_mccue


How about some well chilled cole slaw?

You'd need the CD101 with the refrigeration option.

mike_mccue

Hey, it's Monday... how did the Pork turn out?

Shirley it needs another 3 days cooking time yet?

Karyn

mike_mccue

Hey, it's Monday... how did the Pork turn out?

Shirley it needs another 3 days cooking time yet?