Equipment ground floating at 133v AC - Page 1
Forum section: electronics / beginners

author: gb243
author_rank: Contributor
timestamp: January 25, 2015, 08:46:26 am
content: I last played with electronics almost 40 years ago so am rusty to say the least. I have been buying some kit to start learning again. One item is a siglent SDG1025 signal generator. This morning whist plugged in but switched off the ground of the test probes bit me. I measured 135VAC between the equipment ground and earth.Putting a 100k resister between equipment ground and mains earth I was unable to measure any voltage drop accross it. I have yet to tie the earth lugs of the test gear to earth. Even then I was not expecting to be bitten by touching the probe ground or the ground lug. Is that normal? I will wire everything up into a spider earth to mains ground. Should I leave it at that or rip the covers off and see if there is anything nasty inside?BTW this is central european electrics which are dreadful. A country where fusing the neutral line is considered sensible. The mains earth is probably clipped to a plastic water pipe for all I know.

author: Monkeh
author_rank: Super Contributor
timestamp: January 25, 2015, 09:34:01 am
content: There's no point wiring anything to earth, because you don'thaveearth.Get your installation fixed.

author: Tepe
author_rank: Frequent Contributor
timestamp: January 25, 2015, 09:48:34 am
content: Quote from: gb243 on January 25, 2015, 08:46:26 amWhich country is that?

author: RJFreeman
author_rank: Regular Contributor
timestamp: January 25, 2015, 09:49:04 am
content: hmmmm, I noticed something similar on an HDG 2002 - the output is floating and is not actually grounded.Continuity test from the ground pin on the IEC connector and BNC output confirm this.I have not really had time to investigate further yet.

author: mij59
author_rank: Frequent Contributor
timestamp: January 25, 2015, 10:08:40 am
content: Hi,Don't think there's something wrong with the function generator, as said the output is floating.The voltage you measure is due to the high impedance of the measuring device and the capacitive coupling of the function generator to means.

author: Monkeh
author_rank: Super Contributor
timestamp: January 25, 2015, 10:16:25 am
content: If the voltage does not go away when given a path to earth, something is wrong. Like no earth.Also, the front panel seems to clearly state the outputs arenotfloating.

author: tautech
author_rank: Super Contributor
timestamp: January 25, 2015, 10:27:45 am
content: Just checked my SDG1010 demo unit:BNC's to Mains GND: 0 OhmsGND terminal on rear AWG to IEC mains socket: 0 OhmsYou have a serious problem with your house wiring, GET IT FIXED

author: gb243
author_rank: Contributor
timestamp: January 25, 2015, 11:22:51 am
content: I have created a mains earth connection to the function generator and scope. Seems to have sorted everything. A few twitches with the generator have gone away (eratic operation). So all seems fine. The country is Switzerland. I had a mains fuse blow so nothing in the flat worked but there was mains live still going to various sockets and kitchen appliances. I had a new distribution panel and the entire flat tested out recently and it passed. So no where near as strict as in the UK but I have to live with it.

author: gb243
author_rank: Contributor
timestamp: January 25, 2015, 11:47:39 am
content: Sorted. The mains cable provided by Siglent has a strange flat pinned plug. The adapter they provide has no earth. I did not use that but another adapter. The flat earth pin is so thin it only sometimes makes an earth connection. Throw away the cable and adapter and use a proper cable and everything is fine. I will keep the earth hookup now that I have fitted it. Odd that Siglant provide an uneartherd adapter.

author: tautech
author_rank: Super Contributor
timestamp: January 25, 2015, 06:02:46 pm
content: Quote from: gb243 on January 25, 2015, 11:47:39 amGood you fixed it.Siglent will supply the correct IEC cable for anywhere in the world.Your supplier hasn't provided you with the correct one.

author: Richard Crowley
author_rank: Super Contributor
timestamp: January 25, 2015, 06:38:14 pm
content: Please add your country to your user profile. It is a critical piece of information for many discussions.

author: dan.soethe
author_rank: Contributor
timestamp: January 26, 2015, 08:04:46 pm
content: I had an old oscilloscope that had a hot chassis but had a two prong plug so I flipped the plug the other way. then the buzzing on the back of my fingers as I touched the case wasn't there anymore.