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Old 03-11-2011, 02:42 AM   #1
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Default Temp sensor fluctuation

I need to calibrate mt temp sensors on my new rig.
I am using Brewershardware sensors with a BCS.
The first problem I ran across, was the temps fuctuating approx 7 degrees.
With the sensor in an insulated mug,with ice water, My old digital thermometer stays steady 37.5 degrees, BUT, the temps read by th BCS change a few tenths at a time, and over the course of maybe 30 to 45 seconds (didn't time it)it went from 33 degrees to 40 degrees and back.
Any advise?

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Old 03-11-2011, 12:25 PM   #2
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It sounds like you're picking up noise, but I hesitate to say that because the brewershardware stuff tends to be really well made.

Are all of your connections good and clean? Is your probe and wire away from anything that would generate noise?

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Old 03-11-2011, 02:02 PM   #3
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I don't know where it could pick up anything.
Last nights test, nothing was running except the BCS. No elements,no pumps, nuttin.
The rig is not near any other applainces, ect.

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Old 03-11-2011, 02:36 PM   #4
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Did you update the temperature probe settings for the Brewers Hardware probes? The BCS ships w/ coefficients that match our probes, the BH probes have their own set. If you try to use settings that don't match the probes you'll get erroneous readings.
http://www.brewershardware.com/tempe...tructions.html

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Old 03-11-2011, 02:46 PM   #5
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Hmmm.... the sensor wires run through a DB25 cable along with the trigger lines for the SSR's. That DB25 is shielded though so it shouldn't be picking up any noise, and all the lines are low voltage DC.

maybe try using the coefficients from Derrin again and see what happens.

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Old 03-11-2011, 06:31 PM   #6
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Thanks for the compliment Malfet!

Layne, I sent you the actual spec sheet from Vishay on the thermistors used to build the probes and the coefficients I came up with and have been using are here: BCS Temperature Probe Instructions

If there does turn out to be a problem with my sensors I'll get them replaced asap.

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Old 03-11-2011, 06:48 PM   #7
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Is it typical for the temp to 'move'?
My handheld digital thermometer stays steady for minutes ant a time, but all 4 of the temps on my BCS creep up and down. This can't be right.

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Old 03-11-2011, 06:53 PM   #8
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Quote:
Originally Posted by Layne View Post
Is it typical for the temp to 'move'?
My handheld digital thermometer stays steady for minutes ant a time, but all 4 of the temps on my BCS creep up and down. This can't be right.
It depends what you mean by move. In fully analog systems, there will always be a little bit of noise, and even in digital terms you can expect to see a sensor flip-flop a high and low bit when between readings. That should be small, though. How much depends on your system, but generally it should be less than a degree (possibly much less). Your digital thermometer has this too, though it might have some kind of display hysteresis to prevent you from seeing it. If you are getting a 7 degree swing, something is wrong.
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Old 03-11-2011, 06:55 PM   #9
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Just looking at every possibility.
I have wireless surround sound in the brewroom. Could that possibly cause interference?

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Old 03-11-2011, 07:00 PM   #10
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Quote:
Originally Posted by Layne View Post
Just looking at every possibility.
I have wireless surround sound in the brewroom. Could that possibly cause interference?
I guess in theory, but (like Boerderij mentioned) it seems unlikely if everything is shielded. My money is on some kind of configuration error or some kind of power stability problem. I'm not very familiar with the BCS, though, so I'll leave that for others to speculate.
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