Made my 1st meter datum point this evening! - Page 1
Forum section: electronics / general

author: Terry01
author_rank: Frequent Contributor
timestamp: March 09, 2018, 09:42:34 pm
content: So I made my 1st check and recording of data from all my meters this evening.It's nothing that I need dead on scientific results for. It's just a point of reference I can check in on every now and then and make sure none of my meters are drifting too much.I only have 1 of those £10 Chinese voltage reference modules but I think it'll do for what I need. Again, I know it won't be exact every single time I check but ....how much is an acceptable amount of drift to expect and how often should I check them? I took a note of the date, time and temp just so I have a point of reference.I will do the rest of the measurement ranges tomorrow ,i'll just keep the resisters and caps etc I use in a tub so I use the same ones each time. I know it's not going to be anything exact but it'll give me something to go from.I have a Fluke 289, Brymen 867s, Fluke 177, Extech EX505 and Hyelec MS89 so quite a mix from cheap crap to decent. The only 1 that differs from the rest is the Extech which is near enough 1% lower than the rest on all the measurements.Is there anything else I should add to my check list or whatever?

author: Brumby
author_rank: Unknown
timestamp: March 09, 2018, 11:02:31 pm
content: Did you make a note of the temperature at which these measurements were taken?While it may not make alotof difference, it is good practice to do so.

author: Terry01
author_rank: Frequent Contributor
timestamp: March 10, 2018, 02:54:40 am
content: Quote from: Brumby on March 09, 2018, 11:02:31 pmYes I took the temperature and left the module on for 15 mins first. I left the meters on for 10 mins too. I have noticed the 289 makes a more stable measurement if I leave it on for 5 mins 1st. The other meters don't seem to bother so I don't know why the 289 does. It's only a tiny difference but it all counts when i'm checking for drift. I wouldn't do that normally but will when I test them again. It may have all been in the module warming up but I thought for sure the 289 needed a little warm up too.How often do you suggest is good to test them?

author: VK5RC
author_rank: Unknown
timestamp: March 10, 2018, 06:29:30 am
content: Ah, the beginning of volt-nuttery! HiHi.I have found some of the cheap modules quite good to 5 digits or so. The DMMcheck is also pretty good, comes with calibration and includes several resistors and AC volts as well, not cheap though.Some other things to consider apart from temperature, include lead quality and connection cleaning.Good measuring!

author: Terry01
author_rank: Frequent Contributor
timestamp: March 10, 2018, 12:18:30 pm
content: Quote from: VK5RC on March 10, 2018, 06:29:30 amI only have the cheap AD584 voltage reference. I've had it for about 18 months or there about and don't think it has drifted that much if any at all. I've used it for all my meters as I've got better more accurate instruments.It's good to have something as a datum point to work from. I just made an Excel file so it's easy to update and compare. I will add to it as I get more stuff to check against.How often would you suggest is good to check them?

author: VK5RC
author_rank: Unknown
timestamp: March 12, 2018, 09:54:37 am
content: I am no Volt-nut expert - I would tend to look at the calibration cycles the manufacturers recommend - often annually - and then consider measuring your references at least twice as often. Graphing it with Excel (including temperature) will help you see if your reference is drifting - ie all the meters' reading drift in one direction or, one or more meters drift - in which case the 'average' of the meters should be flat - or perhaps combinations of both!!I would strongly recommend reading some of the Metrology posts - there are some VERY serious guys eg TiN, Andreas, Edwin Pettis (makes lovely hand made low temp co resistors), CalMachine, Dr Frank just to name a few. They give away a lot of real experience and knowledge in this complex area in their posts.Robert

author: Terry01
author_rank: Frequent Contributor
timestamp: March 12, 2018, 06:51:56 pm
content: Quote from: VK5RC on March 12, 2018, 09:54:37 amCool, thanks Robert!I'll look in on the Metrology section for sure. I have as many handheld meters as I think i'll ever have. My next stop will be a decent bench meter with a better reference standard somewhere in between. I may even try and build something myself but we'll see.I like the look of either of the Fluke or Keysight 6 1/2 digit meters. I think I prefer the look of the Fluke but would be happy with either....for now!After that you start getting into funny £££'s for the next step and so on.