Calibration    AC50V    - Page 1
Forum section: electronics / testgear

author: hongthiet1994
author_rank: Contributor
timestamp: May 09, 2019, 03:24:37 pm
content: I calibrated my DMM 121GW with AC50VVideo calibrationhttps://youtu.be/xKkBathf3tIBut value show on DMM is not zero when probe is open: value is 5v to 6Vcan you watch videohttps://youtu.be/S4BvfYfo0Bki think it can have noise but 5v to 6v are too bigCan you show your DMM?I don't know what the problem is my DMM.Please help me

author: Specmaster
author_rank: Super Contributor
timestamp: May 09, 2019, 04:42:38 pm
content: Where are your videos? how can we offer any advise when we don't actually know what the issue is?

author: hongthiet1994
author_rank: Contributor
timestamp: May 10, 2019, 02:15:41 am
content: sorry, i public my video

author: Specmaster
author_rank: Super Contributor
timestamp: May 10, 2019, 06:31:32 am
content: Quote from: hongthiet1994 on May 10, 2019, 02:15:41 amSorry but I do not understand, if your videos are public then we can all see them but I'm getting is a message telling me that the video is not available?

author: Specmaster
author_rank: Super Contributor
timestamp: May 10, 2019, 06:42:32 am
content: Sorry I don't know how to calibrate that meter but I think that you may have got something wrong because it reads, with the probes connected to the transformer, 5.00000 volts and the left meter reads 50.02 volts??

author: Candid
author_rank: Regular Contributor
timestamp: May 10, 2019, 06:08:40 pm
content: Quote from: hongthiet1994 on May 09, 2019, 03:24:37 pmSorry but this is not true. You got a well calibrated DMM (well I hope you got) but what you made is you killed your calibration. For calibrating this DMM you need:1. a high accuracy source2. to know how to calibrate this DMMWith your videos you showed us that both of these points are not given and so your DMM now is well off calibration. You may contact the seller for a calibration service or for exchanging the device or you try to find a local calibration service that can help you.

author: NoisyBoy
author_rank: Frequent Contributor
timestamp: May 11, 2019, 04:12:36 am
content: I agree with Candid.You have asked the same question repeatedly on this forum in various threads after you erased your calibration file. You cannot do any sort of "calibration" on a 121GW with a cheap AC supply and a $10 DMM as a standard, I doubt anyone can help you to fix your meter no matter how well intended the community is. Many have shared with you on what equipment you need to do the work on the other threads you had opened. If you do not have access to them, you need to send it to someone who knows what they are doing, and with the proper equipment to restore the meter. Or sell it to someone who can fix it to recoup some of your expense. You are just wasting your time and getting yourself frustrated with the approach you are taking.

author: Specmaster
author_rank: Super Contributor
timestamp: May 13, 2019, 09:49:47 am
content: Why on earth did you mess about with it in the first place?, Was it because it displayed different readings to the cheap meter? If so then thats precisely what I would expect it to do, it is after all is said and done in a different league and I'd sooner trust the reading on the 121GW over the cheaper meter.

author: Kean
author_rank: Unknown
timestamp: May 13, 2019, 01:50:26 pm
content: I think the reason for 5VAC is that the offset calibration according to the 121GW manual is meant to be done at 10% of full scale.But based on the video he seems to do the offset calibration with "shorted" probes, and then the full scale calibration at 5VAC?

author: Kean
author_rank: Unknown
timestamp: May 13, 2019, 02:04:42 pm
content: Oh, and the "OFF-E" display shown in the video most likely means Offset Error.I've not played with the calibration on my 121GW, so I think you are actually calibrating the 5VAC range (R0) not the 50VAC range (R1).I think this is the 5V range (R0), so you actually need 0.5VAC for offset and 5VAC for FS.If you then want to measure above 50AC, you will need to calibrate the higher ranges. e.g. 50VAC range (R1) with 5VAC for offset, and 50VAC for FS.You need to clearly label this meter asuncalibrated, as it will never be accurate unless calibrated properly with suitable references of higher specifications that the 121GW itself.