New PID displays a negative temperature -- help

[htuong95]

I ran into issues with my first PID. When I powered up the PID, it will display a negative temperature. Once awhile it will display a temperature of 33 for a couple of seconds and then back to a negative temperature. I've replaced the TC sensor, but it still shows a negative temperature. I've tried disconnecting the ssr from the PID so that only the power and tc wires are connected, but still shows a negative temperature. I've tried swapping the two wires of the TC sensors around, that did not help. Any ideas on what is wrong? Did I get a bad PID off ebay?

Here is the diagram I am using.
117012

[htuong95]

The TC sensor does seem to respond to temperature changes. I dropped the TC sensor in warm water and the temperature does move in the positive direction. Maybe some kind of internal calibration issues?

[htuong95]

I just notice that I might have bought the wrong PID. This one is a 220v only model. I should have bought the 110v-220v model. I guess I am going back on ebay to get another PID. This time it will be the MYPIN PID.

[dikman]

Nothing wrong with the Rex PIDs - as long as you get the right one! You should have got one that uses 85v - 220v, that way it doesn't matter what your input voltage is. The only real problem (for some, not everyone) is that it only reads in Centigrade, not Fahrenheit.

[6bg6ga]

Is the polarity correct on the TC? Is the TC the correct one for the PID? Did you screw around with the settings?

[htuong95]

Is the polarity correct on the TC? Is the TC the correct one for the PID? Did you screw around with the settings?

The polarity of the TC is Correct. Both of the TC's are k type and matches the setting "0000" k sensors on the PID.

[Echd]

Maybe your pot is broken and the PID is fine?

Like... really, really broken? :mrgreen:

[6bg6ga]

Maybe your pot is broken and the PID is fine?

Like... really, really broken? :mrgreen:

If the pot were broken it would have no effect on the reading of the PID. The PID would still show ambient temperature which it would seem its not doing now.

[wyrmzr]

Since you already ruled out the polarity of the TC, and even replaced it, it's got to be the PID. The relay would be very unlikely to cause a symptom like that; typically, they just won't work if they have issues.
Probably a little too much work to run 220 just for your PID? :mrgreen:

[bangerjim]

The casting pot and SSR have absolutely nothing to do with the t/c reading wrong.

I do not know the quality of the controller you bought, but the good industrial ones run on 80-260VAC. If you have a 220V only unit, it will not even light up or run on only 120vac!

You may have accidentally ventured into the setup region of the software and screwed up the scaling. Again I do not know if your controller is that sophisticated.

I would contact the supplier and ask for an exchange or help. The only thing I have ever seen with negative readings (outside of screwing up the configuration areas of the software) is a reverse polarity T/C. I sell/apply these high-end controllers to industry.

bangerjim

[el34]

The casting pot and SSR have absolutely nothing to do with the t/c reading wrong.
bangerjim

Dittos.

And dittos to the rest of Jim's post. It'd be surprising to learn the controller is 220V ONLY, its manual says 100-240.

[Handloader109]

Swap the Tc connections. Mine did this the first time I powered it up..

[Handloader109]

Oops, you tried that. If it is only 220v,you have to get different controller

[TreeKiller]

I just notice that I might have bought the wrong PID. This one is a 220v only model. I should have bought the 110v-220v model. I guess I am going back on ebay to get another PID. This time it will be the MYPIN PID.

Try one if these.
http://www.ebay.com/itm/PID-DIGITAL-TEMPERATURE-CONTROLLER-KILN-FURNACE-OVEN-ESPRESSO-COFFEE-MACHINE-/191333104007?hash=item2c8c577987
They are a lot easier to change the temp than the MYPIN Bid about $11.00 and pay the $16.00 shipping or you can get it for $40.00 and free shipping. might have to bid on more than 1 to get it for $11.00

[htuong95]

Thanks for the recommendation. I already bought a MYPIN TA4 for $22 shipped from a California Ebay seller. It will be here in the next couple of days.

[dikman]

TreeKiller, that's a nice looking PID, but the shipping is pretty high, coming from Hong Kong! Everything I've bought from HK has always been free shipping.

[el34]

Thanks for the recommendation. I already bought a MYPIN TA4 for $22 shipped from a California Ebay seller. It will be here in the next couple of days.
Which model? TA4 _ _ _

[bangerjim]

TreeKiller, that's a nice looking PID, but the shipping is pretty high, coming from Hong Kong! Everything I've bought from HK has always been free shipping.

You either pay the shipping in the cost of the unit or as shipping. NOTHING in this olde world is free. The cost is in there somewhere.

$10 for a controller is a very good price. But it is like all the other ones...1/16DIN size....pretty much a postage stamp. These old peepers like much larger digits! 1/8 or 1/4DIN is what I will use if...........I ever get the urge to put one of these together. I'm still crankin' out perfect boolits with just the seat of my pants as always.

Glad the OP is getting things under "control"!!!! HA.......ha!

banger

[dikman]

You're quite right, of course, about nothing being free (referring to postage), but when things are put out to bidding a hefty shipping cost is added in case the winning bid is very low. If bidding pushes the price up then the seller has made a bigger profit. I'm referring here to goods out of Hong Kong/China. It's usually better value to just "buy now" once you find the best deal.

The Rex display is slightly smaller than others, but it's no big deal. My aging eyes can still see it clearly enough to see what's happening temperature-wise, and once it's running it just sits there quietly in the corner, so to speak. A bigger display might be nice, but I'm doing this on-the-cheap so it does the job.

"...under "control"......" ah, you're a funny man.:lol: