distance with type J thermocouple wire
distance with type J thermocouple wire
(OP)
Good morning,
What is the maximum distance I can run type J thermocouple wire in a enviroment with an average ceiling temp of 140 degrees? Our plan is to reroute a temp controller to a dry off oven to remote locatation to better control oven temp during times the oven is not required to be on maximum temp settings. With out having to travel to the back of a department to adjust. We have Honeywell digital controllers DC3001.
thank you
2571
What is the maximum distance I can run type J thermocouple wire in a enviroment with an average ceiling temp of 140 degrees? Our plan is to reroute a temp controller to a dry off oven to remote locatation to better control oven temp during times the oven is not required to be on maximum temp settings. With out having to travel to the back of a department to adjust. We have Honeywell digital controllers DC3001.
thank you
2571





RE: distance with type J thermocouple wire
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Sometimes I only open my mouth to swap feet...
RE: distance with type J thermocouple wire
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: distance with type J thermocouple wire
Better? I'm unconvinced! A properly installed thermocouple feeding into a decent quality instrument is fairly immune to external pickup. Power plants are among the electromagnetically noisest places out there except arc furnaces and smelters and we don't often get problems unless we use crappy components, cheap instruments, or don't pay attention to the installation.
Some temperature indicators have a repeater output scaled as 0-10V or 4-20mA to drive an external indicator. If you have a mA output you might consider using that. If it is a voltage output, you're better off either moving the instrument, installing a converter to either digitise the signal into a data stream for RS-485 or ethernet, or else convert it to a mA signal.
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Sometimes I only open my mouth to swap feet...
RE: distance with type J thermocouple wire
Seems, to me, that unless you have a fully DCS facility or a big sterile power-plant that normally appears deserted, it is better to have a controller near the machine so workers can at least occasionally note the temperature/etc.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: distance with type J thermocouple wire
RE: distance with type J thermocouple wire
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: distance with type J thermocouple wire
The spec sheet for that old (pre-1994) UDC 3001 states,
"Common Mode Rejection: Ac (50 or 60Hz): 120 db (with maximum source impedance of 100 ohms ) or ±1LSB whichever is greater.
That would infer that extension wire resistances in excess of 100 ohms would reduce the CMRR. Ungrounding the junction would do a lot to avoid common mode in the first place.
20g J is about 1/3 ohm per double foot, so it does add up.
Dan
RE: distance with type J thermocouple wire
Where'd you find that info Dan?
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: distance with type J thermocouple wire
The 3 ring binder on my book shelf in the single loop controller section.
It's dated Dec 1986, the first issue of the UDC, I believe.
I used a number of them.
It was a great controller, first with universal programmable inputs, could handle electric actuator motors with a slidewire card, even had 7 different functions for a dry contact digital input. Didn't have to send a UDC to the local distributor to have the range re-programmed when switching input types or ranges, like I had to when I used Barber Colman 560's.
But the UDC auto/manual button couldn't be disabled and about 80% of calls from customers were because someone had walked by, popped the controller into manual and no one noticed until the PV drifted to wherever a fixed stable output would put it. Honeywell fixed that in the mid '90s.
Most of those blue bezel units have passed on by now, and I wonder what one gets when buying one on eBay . . .
You need a copy? I can fax or scan and email it.
Dan
RE: distance with type J thermocouple wire
But thank you for your very kind offer. (Much appreciated)
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com