DMM EEVblog 121GW (FW 2.0.5): Wrong period time ("ms") measurement? - Page 1
Forum section: electronics / testgear

author: RK_aus_S
author_rank: Contributor
timestamp: January 26, 2022, 09:43:09 am
content: HiRather accidently, I noticed that myEEVblgo 121GW, FW 2.0.5shows a wrong period time ("ms" milliseconds), for example when mains voltage is applied (here in Switzerland 230 V / 50 Hz). The 121GW shows 10 ms - butshoulddisplay 20 ms (if I understand the function perdiod time right).So I gradually downgraded the firmware and can confirm, that with FW 2.0.2 the period time is correct 20 ms. From FW 2.0.4 on the perdiod time is wrong with 10 ms.Can anybody confirm - or disprove - my observations?Kind regardsRoman

author: armandine2
author_rank: Frequent Contributor
timestamp: January 26, 2022, 10:06:53 pm
content: Reply removed - after getting the OPs point

author: bicycleguy
author_rank: Frequent Contributor
timestamp: January 26, 2022, 11:51:37 pm
content: The ms is the on time of a signal as shown with this 25% duty cycle 50Hz.The manual says:1. Frequency2. Pulse width3. Duty cycle

author: bdunham7
author_rank: Super Contributor
timestamp: January 27, 2022, 12:15:02 am
content: Whether 20ms or 10ms is the 'correct' reading for a 50Hz sine wave depends on whether the measurement is intended to be 'period' or 'pulsewidth'. Typically a DMM will display pulsewidth not period, as the period can be easily inferred from the frequency reading. On p. 48 of the manual it states that it is intended to be pulsewidth, so 10ms would be correct. It appears that they got that wrong with earlier versions and corrected it, not the other way around.https://www.eevblog.com/wp-content/uploads/2017/11/121GW-Manual-5.pdf

author: joeqsmith
author_rank: Super Contributor
timestamp: January 27, 2022, 01:58:34 am
content: The first manual I have shows Period rather than Pulsewidth.***Make that the first several manuals show Period but they start to mix in Pulsewidth. Maybe they couldn't decide what they wanted.

author: RK_aus_S
author_rank: Contributor
timestamp: January 27, 2022, 07:16:02 am
content: HiThanks a lot to you all for clarification.Some firmware release notes would be helpful, so that people like me don't ask potential the wrong questions.But I can't find any official firmware release notes in the web, but maybe I'm just unlucky looking.Has anyone informations how the get/find some firmware release notes to the 121GW? It's obviously a quite open system, so this release notes shouldn't be hidden anyway, right?Kind regardsRoman

author: joeqsmith
author_rank: Super Contributor
timestamp: January 27, 2022, 02:02:40 pm
content: Dave would sometimes post about updates as they became available but I'm not aware of any maintained release notes.I'm playing around with another product that also offers firmware of the week where it would be very helpful to track their changes in a central document. Sadly, we have all noticed a steady reduction in documentation, not just firmware updates but in general.

author: bdunham7
author_rank: Super Contributor
timestamp: January 27, 2022, 02:25:55 pm
content: Quote from: RK_aus_S on January 27, 2022, 07:16:02 amp. 9 and 10 of the current online manual shows the firmware versions and brief notes. No mention of period or pulsewidth.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 28, 2022, 01:10:02 am
content: Quote from: bdunham7 on January 27, 2022, 02:25:55 pmCurrent manual, page 50 shows period. Seems they never sorted out the basics.

author: RK_aus_S
author_rank: Contributor
timestamp: January 28, 2022, 05:59:53 am
content: Does anyone see a way to forward this to Dave? And you could also use this opportunity to ask him to provide firmware release notes for the future.I wrote Dave a personal email before this thread. Sometimes he answers - in this case not...