Deciphering the Function of Old Power Station Equipment

[sophiecentaur]

I saw these two displays in Poole Town Museum. They came from the old local power station.
The Frequency Meter appealed to me. I assume it works on the resonance of vibrating reeds and the white end(s) of the reeds at or near resonance will vibrate but the others will not.
I'm sure Jim will like these, even if they don't appeal to anyone else.

 

[mishima]

Hmm, could it be possible to build an electrical frequency meter like that for a low cost?

 

[sophiecentaur]

A bit labour intensive, I would think. (Of course, you have one of those in your ear!)

 

[dlgoff]

I saw these two displays in Poole Town Museum. They came from the old local power station.
The Frequency Meter appealed to me. I assume it works on the resonance of vibrating reeds and the white end(s) of the reeds at or near resonance will vibrate but the others will not.
I'm sure Jim will like these, even if they don't appeal to anyone else.

I think you wrote what's in bold just to get my reaction.

 

[mishima]

Sure, and computer soundcard; but for frequencies above 20kHz that would be nice with even +-1000 Hz accuracy. Ill check the old journals at uni library for something like it...

 

[davenn]

Dang Sophi. I was going to say ... don't talk too loud else Don will hear you and will want them

but its too late, he's already heard haha

Dave

 

[davenn]

but that meter is reading flow rates and RPM, not frequency

 

[jim hardy]

That's an interesting meter : 1% resolution. i never saw one with so many reeds.

At first the 3000 rpm midscale threw me - but of course it is, you're 50 hz.

There's a lot fewer ways for that one to fail than in a fancy electronic one.

We kept one with a magnetic mount on our turbine front casing. It had no wires - needs no voltage since vibration from the machine is plenty to excite the reeds. Always check the electronic meter against that one before starting any test. Our overspeed trip was set at 111% which would be 3330 for 50hz... on your meter bottom row fourth reed . Ours was 60hz 4 pole, 111%=1998 RPM.

The reeds adjacent will indeed vibrate but at less amplitude. So you get an eye shaped display centered on correct frequency.



Thanks Sophie !

 

[sophiecentaur]

but that meter is reading flow rates and RPM, not frequency

Tut Tit. Read what it says on the tin, dear boy. The label is for three exhibits - and the gauge is marked in RPM.

 

[anorlunda]

Most engineers enthusiastically subscribe to the KISS principle; but they repeatedly forget to apply it in real life.

That RPM meter illustrates the KISS principle. Not only that, it is highly reliable and redundant. Even if one of the reeds breaks, that does not affect the others. It is easy to protect from over/under voltage or frequency or G forces, cyber attack, and so on. Watching the meter, the operator can not only see the current RPM, but the trend and (within a certain band) the noise levels of the signal.

I recently visited a brand new ultra-modern regional control room for the US power grid. It made use of countless computers, video screens, and a 150x50 foot video wall. Yet the backup of the backup is still a bunch of analog recorders and simple analog devices, wired to remote analog sensors scattered around the region, and wired back to the center with dedicated analog copper wires. One signal, one wire for hundreds of miles and supposedly following diverse routing paths.

When the consequences of complete failure are intolerable, the KISS principle prevails.

 

[sophiecentaur]

Hmm, could it be possible to build an electrical frequency meter like that for a low cost?

Did you look at what's available on the better class of DMMs? Crude RC based measurement, I think but much better than nothing.

 

[jim hardy]

Yet the backup of the backup is still a bunch of analog recorders and simple analog devices, wired to remote analog sensors scattered around the region, and wired back to the center with dedicated analog copper wires.

Ours was an old plant, completely analog.
Actually those three black controllers immediately below operator's hand are pneumatic. Old fashioned, but completely immune to RFI and Stuxnet.

photo courtesy of argental...

That's a good combination - a robust analog system with a sophisticated computer to monitor and troubleshoot it . Our analog equipment outlasted four generations of computers.

I repaired computers long enough to appreciate their failure modes. Hence my signature.

old jim

 

[davenn]

Tut Tit. Read what it says on the tin, dear boy. The label is for three exhibits - and the gauge is marked in RPM.

I don't follow ??

ohhh you were referring to a freq meter (that wasn't in the pic) but showing a rev counter
that's a great way to confuse this poor ol' fart haha
D

 

[davenn]

NOOO, Not the RED Button ... Don't push the red button !

Sorry Jim ... my nutty sense of humour ... I couldn't resist !


Dave

 

[sophiecentaur]

I don't follow ??

ohhh you were referring to a freq meter (that wasn't in the pic) but showing a rev counter
that's a great way to confuse this poor ol' fart haha



D

I see the confusion. Well, the meter measures frequency and my Electronics Engineer brain made me write that down and not RPM indicator. Still a damn clever 'little' engine.