NTC Probes STC 1000

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Rhodesy
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NTC Probes STC 1000

Post by Rhodesy » Sat Feb 28, 2015 10:29 am

Apologies in advance but as per my previous posts I am not very swavvy when it comes to d.i.y. electrics. I purchased an NTC from MrLard which I would like to wire into my already assembled STC unit. I notice that there are 3 clips connections on the wire. The STC unit has 2 ports for the a probe to be connected. What I wanted to check was if this can be wired and secondly how to do so. As I said above I am not really experienced at all with this sort of thing so apologies for what may be a stupid question.

I plan to connect the probe to my conical fermenter to control my brew fridge.

http://brewbuilder.co.uk/index.php?_a=p ... duct_id=98

Belter

Re: NTC Probes STC 1000

Post by Belter » Sat Feb 28, 2015 3:35 pm

Are you sure you don't have a Pt100 there? I see there are options for either in the drop down list

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Re: NTC Probes STC 1000

Post by LeeH » Sat Feb 28, 2015 4:17 pm

Yep, you have bought a PT100.
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BenB

Re: NTC Probes STC 1000

Post by BenB » Sat Feb 28, 2015 7:41 pm

Yup regardless of what you ordered that's not what you need. It (PT100) will work very nicely with a PID like the Sesko / Auber but you need a two wire NTC... Sorry! The NTC probe just measures the resistance across the bulb so you shouldn't shorten or extend the cable or add additional junctions / connectors as you will impact on the reading. The PT100 has the two wires across the sensor but an additional return line which bypasses the sensor- this gives a "reference" so the sensor resistance can be worked out despite any changes to the resistance due to cable length and / or connectors.

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NTC Probes STC 1000

Post by LeeH » Sun Mar 01, 2015 10:04 am

BenB wrote:Yup regardless of what you ordered that's not what you need. It (PT100) will work very nicely with a PID like the Sesko / Auber but you need a two wire NTC... Sorry! The NTC probe just measures the resistance across the bulb so you shouldn't shorten or extend the cable or add additional junctions / connectors as you will impact on the reading. The PT100 has the two wires across the sensor but an additional return line which bypasses the sensor- this gives a "reference" so the sensor resistance can be worked out despite any changes to the resistance due to cable length and / or connectors.
Mmmmm, not quite.

They both work the same way, just have different materials and range. A PT being the widest.

Both can be extended and jointed, that's why instruments have differentials/calibration functions on them.

The 3rd wire on a PT is not a by pass, it's used to lower the resistance of the conductor on long runs. It's joined directly on the other side of the bulb with the other. So, on a long run say 200m across a factory floor you would use a 3 core cable.

BOTH have to be calibrated with an accurate known source such as a thermopen as they have calibration certs. I have had STC's that have been close to 2 degrees out.
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Rhodesy
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Re: NTC Probes STC 1000

Post by Rhodesy » Sun Mar 01, 2015 12:11 pm

Thanks, I can assure you that I ordered an NTC as at least checked that much in terms of the STC 1000. I'll contact Brew Builder.

Appreciate the clarification.

Rhodesy
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Re: NTC Probes STC 1000

Post by Rhodesy » Sun Mar 01, 2015 1:02 pm

Spoke with MrLard who advised that all probes come with 3 wires regardless. All that is required is one of the red wires is used when connecting to the STC1000

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Re: NTC Probes STC 1000

Post by Fil » Sun Mar 01, 2015 2:06 pm

Rhodesy wrote:Spoke with MrLard who advised that all probes come with 3 wires regardless. All that is required is one of the red wires is used when connecting to the STC1000
well well now we know.. i too thought perhaps it was a pt100 shipped/ordered in err
ist update for months n months..
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AnthonyUK

Re: NTC Probes STC 1000

Post by AnthonyUK » Sun Mar 01, 2015 2:30 pm

LeeH wrote:They both work the same way, just have different materials and range.
I thought they worked exactly opposite in that the NTC = negative temperature coefficient and a PT100 is positive.

Belter

Re: NTC Probes STC 1000

Post by Belter » Sun Mar 01, 2015 4:24 pm

My latest Stc has three terminals for the sensor.

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LeeH
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Re: NTC Probes STC 1000

Post by LeeH » Sun Mar 01, 2015 5:15 pm

AnthonyUK wrote:
LeeH wrote:They both work the same way, just have different materials and range.
I thought they worked exactly opposite in that the NTC = negative temperature coefficient and a PT100 is positive.
They both work on resistance as you know. That was my point.
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AnthonyUK

Re: NTC Probes STC 1000

Post by AnthonyUK » Sun Mar 01, 2015 6:12 pm

LeeH wrote:They both work on resistance as you know. That was my point.
I didn't want people to assume they are interchangeable :wink:

BenB

Re: NTC Probes STC 1000

Post by BenB » Sun Mar 01, 2015 11:34 pm

LeeH wrote:
BenB wrote:Yup regardless of what you ordered that's not what you need. It (PT100) will work very nicely with a PID like the Sesko / Auber but you need a two wire NTC... Sorry! The NTC probe just measures the resistance across the bulb so you shouldn't shorten or extend the cable or add additional junctions / connectors as you will impact on the reading. The PT100 has the two wires across the sensor but an additional return line which bypasses the sensor- this gives a "reference" so the sensor resistance can be worked out despite any changes to the resistance due to cable length and / or connectors.
Mmmmm, not quite.

They both work the same way, just have different materials and range. A PT being the widest.

Both can be extended and jointed, that's why instruments have differentials/calibration functions on them.

The 3rd wire on a PT is not a by pass, it's used to lower the resistance of the conductor on long runs. It's joined directly on the other side of the bulb with the other. So, on a long run say 200m across a factory floor you would use a 3 core cable.

BOTH have to be calibrated with an accurate known source such as a thermopen as they have calibration certs. I have had STC's that have been close to 2 degrees out.
true. I was confusing my ntc with my k-type thermocouples. Feel free to ignore :)

sparky Paul

Re: NTC Probes STC 1000

Post by sparky Paul » Mon Mar 02, 2015 12:11 am

LeeH wrote:The 3rd wire on a PT is not a by pass, it's used to lower the resistance of the conductor on long runs.
Not quite. BenB is actually correct regarding the use of the third wire, but 'by pass' is perhaps not the best way to describe it... the third wire is a compensation leg, it is used on long runs so the the controller/indicator can account for any intermediate wiring or connections.

It works by effectively subtracting the resistance between two red wires (to one end of the PRT and back) from the resistance between white & red wires (to the PRT, going through the PRT and back), to calculate the actual resistance of the PRT element. That way, any intermediate wiring has negligible effect on the measurement.

All resistance thermometers like NTC, PT100, etc. can be 2 or 3 wire configuration.

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Re: NTC Probes STC 1000

Post by LeeH » Mon Mar 02, 2015 5:44 pm

Every day is a school day!
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