Tektronix vs RCD

[Roderick]

I have recently added a few Tektronix waveform / vectorscopes to my edit suite, but they keep tripping my RCD's which is rather annoying!

Each unit tests fine, with my basic tests, but when I plug more than 3 in at the same time, the RCD trips. And it can be any combination of units.

What I have are a 1721 & 1731, a couple of 1741A's, a 1765 and a 1781R.

 

Has anyone else had this problem? Is there a solution?

At the moment I am considering running in a separate feed just for the monitoring gear to fix the problem, but I am still curious what causes this.

Are Tektronix units known for high leakage problems? I can't find any data on this, let alone any fixes.

 

Cheers, Roderick

[boatman]

It will be the mains filters. Tektronix scopes and vectorscopes have always been a problem, even when I first worked on installations in Television Centre 40+ years ago. In an edit suite, which is a non-d0me$tic environment, couldn't you use a 100mA RCD on a radial circuit?

[KevinE]

I'm 'currently' changing the workshop 30mA RCD to individual RCBOs for this very reason. When the PC, photocopier, laser printer, CCTV system, fax and Eprom programmer are all on at the same time, the RCD will go out and refuse to reset until I unplug one or more of the aforementioned appliances.

 

There is so much filtering that I'm sure I'm dumping hundreds of pounds worth of power down the earth lead...where's the green lobby when you need them?

[djandydee]

I have just tested a 1781R just to see if these things leak like crazy but the PAT has come back with <0.01mA.

 

Could some of those units be Ex BBC and have had a life in an OB truck? Our trucks pop breakers until the kit is warmed up due to damp conditions. Just a thought

[Roderick]

Thank you all for your quick responses!

It does confirm what I thought and running a separate feed will hopefully fix the issues. At present it is all running of the same supply as the office with the usual equipment.

As I am running this all in the back of my house, not sure if I can put in a 100mA RCD but I will ask the sparky that will be installing the GPO's.

Some of the gear came from an Australian OB company so probably had a life in a truck... But it has been sitting here for a few days whilst I cleaned and calibrated it.

 

On the subject of earth leakage, does anyone know of a affordable monitoring read-out?

I would be interested to see how much the various bits of equipment drain/leak, but preferably for less than A$1000!

 

Cheers

Roderick

[J Pearce]

A clamp meter round an earth wire should do nicely.

 

Build a power loop box (power in one end, power out the other) with singles internally then mount your clamp for the clamp meter round the earth wire.

[Martin]

Many PAT machines will do earth leakage.

 

If you go down the clamp meter route, you will need a meter capable of measuring in the mA range such as the Fluke 360. Most standard clamp meters will only go down to 0.1A (100mA).