jelynch@hubcap.clemson.edu (james e lynch) (04/26/91)
Please Help !
I'm constrained to use a type K thermocouple to measure temperature. The thermocouples output has to be digitized but not displayed (it feeds into a data acquisition system). I am willing to add an ADC to the data acquisition system, but I need some help going from the thermocouple to copper leads feeding the ADC. Is there a single package solid state device that converts thermocouple signals to mVolts (that is, a device that has the compensation for the terminal dissimilar metals potential). Or better
yet, a simple and cheap pre-packaged thermocouple in / digital out board module. I realize that equipment to perform the task is available from Omega, but I don't need the extra features and most importantly I can not afford the cost.
Please forward all comments to:
jelynch@hubcap.clemson.edugoldberg@oasys.dt.navy.mil (Mark Goldberg) (04/29/91)
In article <1991Apr25.182617.15874@hubcap.clemson.edu> jelynch@hubcap.clemson. edu (james e lynch) writes: >I'm constrained to use a type K thermocouple to measure temperature. >The thermocouples output has to be digitized but not displayed (it >feeds into a data acquisition system). I am willing to add an ADC >to the data acquisition system, but I need some help going from the >thermocouple to copper leads feeding the ADC. Is there a single package >solid state device that converts thermocouple signals to mVolts (that >is, a device that has the compensation for the terminal dissimilar >metals potential). Or better yet, a simple and cheap pre-packaged >thermocouple in / digital out board module. I realize that equipment >to perform the task is available from Omega, but I don't need the >extra features and most importantly I can not afford the cost. Please >forward all comments to: jelynch@hubcap.clemson.edu Some of the equipment makers like Omega and Leeds & Northrup probably have boards to do this. But the boards are ususally designed to be part of data acquisition systems made by these companies. Let's think about what you need to do. First, all thermocouples must have a reference junction at some fixed temperature. The most basic setup puts the reference in an ice bath. I haven't seen too many ice baths around for thermocouple work these days (calibration excepted) since most thermocouples are referenced electronically. The thermocouple electronics must also convert the current vs. temperature releationship to the corresponding temperature. Bottom line for you is that the easiest thing is probably one of those handheld readout devices. There's a company called Precision Digital of Massachusetts (I hope the firm is still in business) that makes a handlheld digital readout with digital outputs. Omega may offer a similar device. Anyway, it displays the temperature on LCDs as well. These units are fairly inexpensive. So it may be cheaper and easier to but a simple readout than to fuss with interfacing a circuit board. =========David Taylor Research Center (a US Navy lab) - Annapolis, MD========== /|/| /||)|/ /~_/\| |\|)[~|)/~_ | "Everyone's entitled to MY opinion." / | |/~||\|\ \_/\/|_|/|)[_|\\_/ | goldberg@oasys.dt.navy.mil "Poor is the man whose pleasure depends on the permission of another."-Madonna
cichlid@leland.Stanford.EDU (David Neiman) (04/30/91)
Try Analog Devices -- I don't know the name of the converter, but they make an all-in-one package for TC-->digital. I'm not sure about the cold-junction compensator, but omega makes one for not too much money. -- This space for rent.
chaplin@keinstr.uucp (chaplin) (04/30/91)
In article <1991Apr25.182617.15874@hubcap.clemson.edu> jelynch@hubcap.clemson. edu (james e lynch) writes: >I'm constrained to use a type K thermocouple to measure temperature. >The thermocouples output has to be digitized but not displayed (it >feeds into a data acquisition system). I am willing to add an ADC >to the data acquisition system, but I need some help going from the >thermocouple to copper leads feeding the ADC. Is there a single package >solid state device that converts thermocouple signals to mVolts (that >is, a device that has the compensation for the terminal dissimilar >metals potential). Or better yet, a simple and cheap pre-packaged >thermocouple in / digital out board module. I realize that equipment >to perform the task is available from Omega, but I don't need the >extra features and most importantly I can not afford the cost. Please >forward all comments to: jelynch@hubcap.clemson.edu About 8 years ago I designed a data acquisition system using just such an IC. It contained a temperature sensor and converted a type T thermocouple signal to 10mV/degC. It was made by Analog Devices, but their latest data book does not list it, and I can't remember the part number. Analog Devices has dropped a lot of products from their line lately. An analog guru friend of mine says that Linear Technology is starting to introduce similar products. You might check with them. -- Roger Chaplin / Instruments Division Engineering / uunet!keinstr!chaplin CI$: 76307,3506 / voice: (216) 498-2815 / FAX: (216) 248-6168 "In the last analysis the customer is the independent auditor. In the merciless light of real use, every flaw will show." - Frederick P. Brooks, Jr.