Help With Pid - Set620 & 2 Wire Pt100

[edoeven]

hey guys Finally getting around to getting my RIMS system going - been aqquiring bits and pieces for what seems like ever, but never actually building the thing.... Anyway - I have a "SET620" pid & 2-wire PT-100 probe (ebay special), along with <random brand> SSR. Wired it up to control a 2.4kw element.

Problem is, the pid just has "EEEE" instead of the current temp. I believe this is a prob with the thermocouple - the PID has 3 connectors, the sensor only two. I have tried (with my limitied electronics knowedge) bridging what I thought was the right connections, but with zero success... the two leads of the probe have approx 10 ohm resistance at ~ 23deg C (iirc), which seems way too low - I don't recall exactly what range the meter was on so gotta check again...

Anyway, attached is a pic of the PID conections... PT-100 has a blue and red (assume - and +), PID has +/- and a third, which the diagram seems to indicate that R is measured over... does anyone else have the same PID/probe combo and can help me out with the correct hookup? or perhaps just knows anyway....? cheers

 

[Mitternacht Brauer]

Hi Likesbeer,

Check the settings on the controller, I believe you have a thermocouple and not a PT100. PT100 should be three or four wire. Thermocouples will be two.If you are not sure of type them set up and try K type or J type as they are the most likely.

I have to be at a meeting but will check back soon with more info.

MB

 

[leiothrix]

PT100's are a resistive device and as such only have 2 wires. If they have 3 or 4 it is to try and compensate for the effects of the first two wires.

So (from memory of wiring up mine, but read your instructions) -- connect the PT100 to 8 & 9, and just connect 9 & 10 together.

Rob.

 

[Harry Volting]

Sounds like your unit requires a 3 wire RTD (two measuring circuits - one as a reference circuit) as opposed to a 2 wire thermocouple.
Thermocouple polarity (IMO) usually features the red lead as negative.
Match the input device and you should be a step closer.
Hope this helps.
Harry

 

[schooey]

Just at a quick look, without googling the models blah blah... your PID seems to have a pic of a resistor across terminals 8 & 9, your PT 100 is a resistance type probe....

I'd try connecting the probe across terminals 8 & 9 and resistors aren't polarity conscious, so swing it which ever way you like....

 

[jjeffrey]

A Pt-100 sensors is a resistive device, which has a resistance of 100 ohms at 0degC. At 23degC, it should have a resistance of about 108.6ohms (see Pt100 resistance table) View attachment Pt100_Resistance_chart.pdf

I also reckon you have a thermocouple, and I reckon it will be type K. Pt100 sensors have 3 or 4 wires, 2 of which are to compensate for lead resistance as mentioned by leiothrix.

If it's a thermocouple, there will be a voltage across the leads of about 1.5mV at 23deg (see type K voltage table) View attachment Type_K_voltage_table.pdf Use your multimeter to figure out which is positive or negative, and wire accordingly to terminals 9 and 10. You will ALSO have to configure the controller for the correct input, as the default is a Pt100. Refer to these instructions on how to set the controller: SET620 Operating Instructions

Cheers,

jj.

 

[schooey]

PT100's are a resistive device and as such only have 2 wires. If they have 3 or 4 it is to try and compensate for the effects of the first two wires.

So (from memory of wiring up mine, but read your instructions) -- connect the PT100 to 8 & 9, and just connect 9 & 10 together.

Rob.

woops... If I had of noticed this, leio, I would have just posted a +1

 

[edoeven]

thanks for the quick replies! jjeffrey was on the money - the probe was labeled "Ca(K),Pt100", confusing eh? - I checked the resistance again, and confirmed nowhere near what a PT100 should be, as well as hooking it up as leiothrix etc suggested, no dice... reset the PID to K type and hooked it up across +/- and appears to be working OK now, thanks a heap

I will chase down an actual PT100 - as the K-type probably isnt the best for lower temp measurements like a mash!

cheers again

 

[jjeffrey]

I will chase down an actual PT100 - as the K-type probably isnt the best for lower temp measurements like a mash!

It won't be attrocious for mashs and mash temps. I'd expect +/- 0.5 of a degree. The temperature in your mash will actually vary by the same amount depending on where you sample, so you might not gain anything by going to an RTD. If you can get a half decent glass thermometer, check the probe against the thermometer in a jug of warm/hot water. You might find that the error isn't too bad.

Thermocouples are susceptable to EM interferrence, so if your temp is swinging around you can solve it by going to an RTD. In most garages, EM radiation isn't an issue (unless you have a CB set-up or a speed controller on your lathe).

Cheers,

jj.

 

[edoeven]

yeah, sensor under my tongue read 37deg - so it seems ok, I just want that decimal point there hah I will see how it goes when in the thermowell / in RIMS tube and how that correlates with the mash temp... looking forward to giving it a test run (water only first time out!)