Ss Brewing Technologies Giveaway!

Home Brew Forums > Home Brewing Beer > Electric Brewing > PID Pv value off 13.5 degrees F
Reply
 
LinkBack Thread Tools
Old 03-04-2011, 03:56 PM   #1
Malintent
Feedback Score: 0 reviews
Recipes 
 
Join Date: May 2010
Location: Ceilin
Posts: 377
Liked 8 Times on 7 Posts
Likes Given: 5

Default PID Pv value off 13.5 degrees F

I know how to calibrate.. not a problem. My concern is the amount of offset. 13+ degrees seems excessive. It reads higher than actual (it needs a -13 offset). It is a pt100 RTD on a cheap Auber PID (both bought from Auberins). I cut the very ends of the probe wire off to remove the terminal connectors, then soldered it to a 3 prong socket (also from Auber).

My question is, should I be concerned that this is indicative of a poor solder joint (higher resistance = higher indicated temp), a bad probe, or is an initial 13 degree error on par for what you guys have seen with these?

__________________
Malintent is offline
 
Reply With Quote Quick reply to this message
Old 03-04-2011, 05:20 PM   #2
Walker
I use secondaries. :p
HBT_LIFETIMESUPPORTER.png
Feedback Score: 0 reviews
 
Walker's Avatar
Recipes 
 
Join Date: Sep 2005
Location: Cary, NC
Posts: 11,236
Liked 86 Times on 77 Posts
Likes Given: 11

Default

Quote:
Originally Posted by Malintent View Post
I know how to calibrate.. not a problem. My concern is the amount of offset. 13+ degrees seems excessive. It reads higher than actual (it needs a -13 offset). It is a pt100 RTD on a cheap Auber PID (both bought from Auberins). I cut the very ends of the probe wire off to remove the terminal connectors, then soldered it to a 3 prong socket (also from Auber).

My question is, should I be concerned that this is indicative of a poor solder joint (higher resistance = higher indicated temp), a bad probe, or is an initial 13 degree error on par for what you guys have seen with these?
No.. that seems bad. My cheap chinese RTD has an error of 1.5*F. My even cheaper chinesier probe that ended breaking on me had an error of 3.1*F.

I would think that one from Auber should be pretty damn close to correct.

Did you test the probe with the PID before you cut and soldered through the connector?

The soldering shouldn't be causing you a problem unless your work was really crappy one wire and not the others. The whole point of the RTD's having three wires is to compensate for the resistance in any leads and connectors on the path between the probe and the device using the probe.

If you didn't check it at first with probe directly connected to PID, it might be worth the effort to unsolder the thing and test it directly connected.

13*F seems too much of an error to me, but I AM NOT AN EXPERT.
__________________
Ground Fault Brewing Co.
Walker is offline
 
Reply With Quote Quick reply to this message
Old 03-04-2011, 07:05 PM   #3
Malintent
Feedback Score: 0 reviews
Recipes 
 
Join Date: May 2010
Location: Ceilin
Posts: 377
Liked 8 Times on 7 Posts
Likes Given: 5

Default

I just got off the phone with their tech support. they agree that 13 degrees F is excessive. they also confirmed the 3 lead wire redundancy makes a bad solder joint unlikely (both red leads would have to be nearly equally bad).

there are four possibilities

1) air trapped in the tube by the probe
If the probe is not completely submersed, a HIGH reading is possible (this I didn't quite understand - I would have thought it would be low)

2) My reference thermometer is bad (not likely)

3) I have two bad solder joints. I was told to measure the resistance in Ohms between matching pins on either side of the wire assembly (each 1 Ohm of resistance in both red wires would lead to 1 degree C of error, high.

4) I was sent a faulty probe.

If I eliminate 1 - 3 as the culprit, they offered to exchange the probe out, even though I modified it (with the connector bought from them).

Any other opinions or comments are still very welcome!

__________________
Malintent is offline
 
Reply With Quote Quick reply to this message
Old 03-04-2011, 07:25 PM   #4
Walker
I use secondaries. :p
HBT_LIFETIMESUPPORTER.png
Feedback Score: 0 reviews
 
Walker's Avatar
Recipes 
 
Join Date: Sep 2005
Location: Cary, NC
Posts: 11,236
Liked 86 Times on 77 Posts
Likes Given: 11

Default

1) air trapped in WHAT tube? is this in a RIMS pipe? If so, you can eliminate #1 and just unscrewing the thing and see if it's still off by 13*F.

2) boil water and check it with your reference thermometer and the rtd from auber. should be 212*F.

3) this could also be checked by unsoldering and checking with the probe directly connected to the PID.

__________________
Ground Fault Brewing Co.
Walker is offline
 
Reply With Quote Quick reply to this message
Old 03-04-2011, 10:55 PM   #5
Malintent
Feedback Score: 0 reviews
Recipes 
 
Join Date: May 2010
Location: Ceilin
Posts: 377
Liked 8 Times on 7 Posts
Likes Given: 5

Default

32.0 F on the dot.

I did an ice water check and my refrence thermometer seems to have been damaged recently (my gear has been in storage for the winter). It read around 22 or so in the ice bath.

Yes, Walker, this is a rims pipe... a new project to kick off the season

__________________
Malintent is offline
 
Reply With Quote Quick reply to this message
Reply



Quick Reply
Message:
Options
Thread Tools