High precision thermocouple scanners?  - Page 1
Forum section: electronics / general

author: mzzj
author_rank: Super Contributor
timestamp: October 16, 2021, 03:54:09 pm
content: Got any hints on "metrology grade" thermocouple scanners?Looking for something like 16+ channels, built-in CJC with 0.1...0.2 Cel accuracy.CJC accuracy is usually the weak link in "general purpose" scanners like Keysight 34970A.AFAIK 34970A CJC specification is something like 0.8Cel and it's not performing any better in real life

author: 3roomlab
author_rank: Frequent Contributor
timestamp: October 16, 2021, 04:28:03 pm
content: search for "scanner"https://www.eevblog.com/forum/metrology/scannermultiplexers-for-voltage-references/msg3468296/#msg3468296https://www.eevblog.com/forum/projects/scan-2000-lv-20-a-low-voltage-scanner-card-for-keithley-2000/msg3328264/#msg3328264https://www.eevblog.com/forum/projects/20-channel-diy-scanner-card-for-keithley-dmms-and-daqs/and this is my favhttps://www.eevblog.com/forum/projects/diy-low-thermal-emf-switchscanner-for-comparisons-of-voltage-and-resistor-stand/?all

author: voltsandjolts
author_rank: Unknown
timestamp: October 16, 2021, 05:46:45 pm
content: 34970A + PT100

author: bck
author_rank: Contributor
timestamp: October 16, 2021, 05:52:09 pm
content: Additel ADT 286datasheet is attachedCJC Accuracy is 0.1C

author: mzzj
author_rank: Super Contributor
timestamp: October 16, 2021, 05:57:43 pm
content: Quote from: 3roomlab on October 16, 2021, 04:28:03 pmDidn't see anything specific to my task. I'm looking for thermocouple scanner, not just low thermal EMF scanner.

author: mzzj
author_rank: Super Contributor
timestamp: October 16, 2021, 06:05:31 pm
content: Quote from: bck on October 16, 2021, 05:52:09 pm!Now we are getting somewhere.Actually really good looking unit for temperature cal laboratory with 1 ppm resistance ratio measurement and 8½ digit DMM in one package.Additel didn't even cross my mind so this was exellent tip. (was familiar with their pressure equipment and dry blocks)

author: 2N3055
author_rank: Super Contributor
timestamp: October 16, 2021, 09:14:58 pm
content: https://www.aoip.com/product/benchtop-measurement-and-calibration-instruments/microk-3/not 16 ch though..EDIT:was remembering/looking wrong.. It can be expanded up to 92 channels..

author: miro123
author_rank: Frequent Contributor
timestamp: October 16, 2021, 09:24:54 pm
content: Quote from: voltsandjolts on October 16, 2021, 05:46:45 pm+1 - I think also that PRT or SPRT is the way to go.https://us.flukecal.com/products/temperature-calibration/its-90-temperature-standards/standard-platinum-resistance-thermometI have several questions to the topic starter1. What is your application?2. there are many methods for temperature sensing - /contact and non-contact/. Do you use the right one for your application3. What is the temperature accuracy of termocouple itself?4. How big is the system error of temperature measurement? e.g. contact effect etc.I asking this questions because I want to have clear picture of our measurement setup.PS I have similar experience with HP3497A and thermocouples ~1degree, but that is enought. Most termocouples have higher error than TCJ

author: mzzj
author_rank: Super Contributor
timestamp: October 17, 2021, 03:50:50 am
content: Quote from: miro123 on October 16, 2021, 09:24:54 pmToo many questions and few answers1. Temperature Cal lab UUT readout or data logging for temperature surveys.2. Yes.3. After initial calibration and calculating the correction factors T-type thermocouple is accurate to about 0,05 cel.(NPL calibrated Pt-Au thermocouple is 0,05 degrees! up to 1000 cel and gives good run for your money compared to HTSPRT. )4. Depends on case but I don’t want to get drifted too far. Lets imagine we have SPRT+ASL F900 in calibration bath.

author: LaserEng
author_rank: Regular Contributor
timestamp: October 17, 2021, 06:29:32 am
content: I doubt you could get much better than Isotech's temperature measuring equipment, a MicroK plus a 90 channel expander.Microkhttps://isotech.co.uk/products/microk-precision-thermometry-bridge/Expanderhttps://isotech.co.uk/products/microk-channel-expander/Maybe this whitepaper about cold junction compensation and using a double junction thermocouple will be of interesthttps://isotech.co.uk/wp-content/uploads/2020/09/Double-Junction-Thermocouple-Part-1-1.pdfhttps://isotech.co.uk/wp-content/uploads/2020/09/Double-Junction-Thermocouple-Part-2-1.pdf

author: 2N3055
author_rank: Super Contributor
timestamp: October 17, 2021, 09:13:56 am
content: Quote from: LaserEng on October 17, 2021, 06:29:32 amYep, that's AOIP I linked to..Those are primary lab instruments..