UT61E still CAT III after backlight modification - Page 1
Forum section: electronics / testgear

author: Pluscrafter
author_rank: Regular Contributor
timestamp: November 09, 2018, 09:26:51 pm
content: I have a EU UT61E, because it hasn't backlight, I want to put one in with a toggle switch. Will it remains the CAT III 300V rating or shouldn't I probe mains after that modification?

author: HKJ
author_rank: Super Contributor
timestamp: November 09, 2018, 09:34:08 pm
content: That depends on how you do it. CAT ratings means the equipment is safe with a transient of a few kV (How many depends on the CAT rating), adding a switch that is safe at the CAT level would most likely maintain it.

author: Pluscrafter
author_rank: Regular Contributor
timestamp: November 09, 2018, 09:39:36 pm
content: Will thathttps://www.conrad.ch/de/eledis-1a11-nf1stse-kippschalter-250-vac-2-a-1-x-einein-rastend-1-st-705009.htmldo the job?

author: tautech
author_rank: Super Contributor
timestamp: November 09, 2018, 09:43:28 pm
content: Quote from: Pluscrafter on November 09, 2018, 09:26:51 pmDON'T put yourself at risk !Get a torch, headlamp or another DMM !

author: Nusa
author_rank: Super Contributor
timestamp: November 09, 2018, 11:19:57 pm
content: Quote from: Pluscrafter on November 09, 2018, 09:39:36 pmFor backlight functionality, sure. For any kind of CAT rating, nope. Violating case integrity with a hole is bad enough, but actually inserting a metal object connecting inside and outside...A CAT-III 300V rating is expected to tolerate 4000V transients!I suggest a reed switch inside, and a sliding magnet on the outside to activate it. You might be able to adapt the removable cover for the RS-232 IR port to do this.

author: Pluscrafter
author_rank: Regular Contributor
timestamp: November 09, 2018, 11:38:01 pm
content: Will that keep the integrity off the meter for CAT III and could you use normal LED's instead of SMD-LED's like in examples in the internet ?

author: Mr. Scram
author_rank: Super Contributor
timestamp: November 09, 2018, 11:40:36 pm
content: A CAT rating means the meter passed a physical test. Changing the design inherently invalidates that test, which means the meter loses the CAT rating. This doesn't mean the meter can't be safe, it just means it lost its CAT rating. It obviously also can mean the meter is deadly, that all depends on the design.

author: Pluscrafter
author_rank: Regular Contributor
timestamp: November 09, 2018, 11:51:45 pm
content: Should I modificate it with the reedswitch and will it be safe to use with mains(230VAC).

author: joeqsmith
author_rank: Super Contributor
timestamp: November 10, 2018, 04:03:16 am
content: Quote from: Mr. Scram on November 09, 2018, 11:40:36 pm+1

author: 001
author_rank: Super Contributor
timestamp: November 10, 2018, 09:47:22 am
content: Quote from: Pluscrafter on November 09, 2018, 11:51:45 pmGo simple and safe wayBuy Fluke

author: Fungus
author_rank: Super Contributor
timestamp: November 10, 2018, 11:24:05 am
content: Quote from: Pluscrafter on November 09, 2018, 11:51:45 pma) The UT61E is borderline safe for mains work to start with, I wouldn't use one for regular mains work.b) A Fluke 101 is $45, delivered.

author: Pluscrafter
author_rank: Regular Contributor
timestamp: November 10, 2018, 03:09:28 pm
content: But it would be safe to probe a TV(not the AC/DCadapter) and use a proper meter for mains?

author: Fungus
author_rank: Super Contributor
timestamp: November 10, 2018, 03:45:22 pm
content: Quote from: Pluscrafter on November 10, 2018, 03:09:28 pmAt those voltages on an isolated power supply? Anything can be safe if used correctly.But... it's hard to say without seeing details of the mod.Is there any electrical connection between the switch and an input jack (eg. COM)?

author: Pluscrafter
author_rank: Regular Contributor
timestamp: November 10, 2018, 03:47:30 pm
content: It's a insolated AC/DCadapter.Gesendet von meinem G8341 mit Tapatalk

author: Fungus
author_rank: Super Contributor
timestamp: November 10, 2018, 04:04:34 pm
content: Quote from: Pluscrafter on November 10, 2018, 03:47:30 pmOK then.Is there any electrical connection between the switch and an input jack (eg. COM)?

author: Pluscrafter
author_rank: Regular Contributor
timestamp: November 10, 2018, 04:05:32 pm
content: Quote from: Fungus on November 10, 2018, 04:04:34 pmNoGesendet von meinem G8341 mit Tapatalk

author: joeqsmith
author_rank: Super Contributor
timestamp: November 10, 2018, 05:32:09 pm
content: It seems you have your answer but are searching for people to make you feel better about what you are suggesting. With the number of people who use the internet, surly there are forums loaded with people who would make you feel better about yourself if that is all you are after.There are no guarantees how you or someone else would use the meter in the future. I would have no idea what your skill level is when it comes to making any modifications or in your safety awareness when working with electricity.The fact that you are considering drilling a hole into the case and adding metal to the outside that you would normally come in contact with and asking for a justification doesn't leave me with a lot of comfort. On the bright side, we have Darwin to help sort matters out when humans get too far off track.

author: Pluscrafter
author_rank: Regular Contributor
timestamp: November 10, 2018, 05:38:11 pm
content: Quote from: joeqsmith on November 10, 2018, 05:32:09 pmIt was a stupid idea from me, I was very tired and my mind was off the track.Gesendet von meinem G8341 mit Tapatalk

author: Fungus
author_rank: Super Contributor
timestamp: November 10, 2018, 05:43:58 pm
content: Quote from: Pluscrafter on November 10, 2018, 04:05:32 pmNormally the COM socket is connected to the battery negative terminal inside a meter. I don't know how the switch is wired but there may be nothing between the metal of the switch and COM, or there may be a only a small resistor and LED.Either way I wouldn't like to think somebody was handling the meter when the COM wire was plugged into a mains socket.Basically the modification will convert your meter into a CAT I device - batteries and isolated low voltage DC only.

author: joeqsmith
author_rank: Super Contributor
timestamp: November 10, 2018, 06:02:28 pm
content: Fungus, as I understood it, the metal parts that the user would come in contact with are isolated from the switch contacts. I don't believe I have ever seen a similar toggle switch that was not isolated like this. I doubt these switches are safety rated. What happens when one breaks down? Normally you may have a metal case which is grounded to close the loop but in this case, the person touching the switch may become the return path.You may be able to find a sealed plastic switch that could be a step up. Of course, to make the modifications, someone is running wires inside the meter which could also cause a problem. Outside of education purposes, I can't see any reason to modify a safety rated device.

author: joeqsmith
author_rank: Super Contributor
timestamp: November 10, 2018, 06:11:18 pm
content: Quote from: Pluscrafter on November 10, 2018, 05:38:11 pmWhen people ask, listen, learn and live another day, that's not stupid.

author: Pluscrafter
author_rank: Regular Contributor
timestamp: November 10, 2018, 06:15:16 pm
content: Thats true . With stupid Ideas you learn.Gesendet von meinem G8341 mit Tapatalk