Tempco charting request - Page 1
Forum section: electronics / general

author: IanJ
author_rank: Unknown
timestamp: July 06, 2019, 04:42:58 pm
content: Hi all,I am trying to get some independant data from the following log I recorded via GPIB (3458A)........just wondered if any of you guys have any apps you might be able to throw the data at in order I can see the resultant tempco (ppm/degC) traced out. I have my own VB app but it's not behaving.......For info:-Nominal starting Vdc = 9.999998643Nominal starting temperature degC = 23.49Lowest Vdc recorded = 9.999964499Highest Vdc recorded = 10.00002781Lowest temp degC recorded = 14Highest temp degC recorded = 34Duration of test = 170mins approx.Columns are: Index, DMM, Date/Time, VDC, Temperature, HumidityCSV attached in ZIP.Much appreciate any help.....Ian.

author: TiN
author_rank: Super Contributor
timestamp: July 06, 2019, 05:08:21 pm
content: Here you go.But your temperature excursion is too fast, I'd slow it down 10-50 times to get better confidence in data.

author: dietert1
author_rank: Super Contributor
timestamp: July 06, 2019, 05:36:26 pm
content: Since you are asking for TC, a linear regression over the whole run gives 0,313 ppm/K. Your data show a strange anomaly when comparing temperatures below and above 25°C: Above 25°C there is a hidden variable disturbing the measurement, something like hysteresis.Regards, Dieter

author: IanJ
author_rank: Unknown
timestamp: July 06, 2019, 05:41:41 pm
content: Thanks Tin,So, what I was doing was testing my prototype PDVS2mini design and which uses a novel approach (for me) for the LM399AH mounting.There's no room inside this new enclosure for the 399, and I wanted to keep prying fingers away from it when users change batteries etc......and so, given there's a wee LCD on the outside I mounted the 399 under that. However, rather than open air, (uggghh!) where it might also pick up noise from the LCD etc....... I 3D printed a wee cover (thermal shield) for the 399 using "conductive PLA" it's connected to GND. The conductivity seems to be a couple K across it's length.Anyways, 3ppm over 10degC change works out better than I thought it would.......but I will work on re-testing per your suggestion.Thanks again.Ian.

author: IanJ
author_rank: Unknown
timestamp: July 06, 2019, 05:43:11 pm
content: Quote from: dietert1 on July 06, 2019, 05:36:26 pmYes, this is what was catching me out also (in my own VB)........I will re-test, but I suspect the temp sensor I am using......I'll try removing it's cover and see if that reduces the hysterysis.Could be the chamber going into 'heating' mode also above 24degC, the humidity goes all over the place then........maybe if I slow things right down it will improve.Thanks,Ian.

author: TiN
author_rank: Super Contributor
timestamp: July 06, 2019, 05:58:05 pm
content: Will be there "maxi" version? I'd be interested in one with LTZIf you want, I might have just enough equipment to test your box for TC/INL/stability (if not in rush, time is scarce).

author: IanJ
author_rank: Unknown
timestamp: July 06, 2019, 08:40:13 pm
content: Quote from: 3roomlab on July 06, 2019, 07:24:37 pmNot quite......it all happens in the box. Peltier cooled/heated home built enclosure. All the data is recorded whilst the PDVS2mini is in the sealed box. I have a USB hi-res temp/humidity sensor in there also.I don't have any proper control over the temperature as yet......just the switch on the top and manually playing with the 15V supply (10A).It's capable of cooling down 12degC below ambient. On the inside are a couple of fans on the peltier heatsinks to move the air.Photo with door open.Ian.

author: TiN
author_rank: Super Contributor
timestamp: July 07, 2019, 05:53:16 am
content: Ian, perhaps you can hunt down controller like ILX LDT-5910Bor Arroyo box likethis oneto have control over temperature.

author: IanJ
author_rank: Unknown
timestamp: July 07, 2019, 10:07:44 am
content: Thanks TiN I will take a look.......interesting I could get one thats GPIB controlled which means I could integrate the control functionality right into my GPIB logging app......hmmm!Meanwhile, here's my own graph based on the log data.......still have to fix the tempco ppm/degC display functionality which is broke.Yellow = 3458A loggingRed = Temperature degCGreen = %RHWhite = Calculated ppm variation