Electric meters with pulse output. Seals.

[RMIM]

Hi,

At the moment I have an old mechanical pound coin meter that I use for secondary billing. It's limited as it can only hold about 7 days worth of electric (80kwh).

I was going to buy a new secondary meter that had pulse output and rig it to an electronic coin meter that I would make.

Don't worry the secondary meter would be hooked up by a (qualified) electrician - I'm just going to mess about with the pulse output it produces. (safe and legal right?).

I noticed that the existing meter already had pulse output - sadly I think to get access to the terminals of the pulse output (1000 pulses per kwh) you have to break the seal.

Would the electric board (british gas) let you make use of this output if you contacted them? Can an electrician break the seal for you and attach the wires and re-seal the main meter?

Thanks.

edit:
Or does anyone know of any non-intrusive way of monitoring kwh. I already have those meters that clap around the live wire, im not sure of its accuracy. Plus it does not have pulse output - I would need that to link to a coin meter, my electronics knowledge would only stretch that far. It would be hard for me to open the unit up and try to get the kwh info from the unit.

 

[bernardgreen]

If the new meter has the LED that pulses at ( I think ) one pulse every 0.1 Kwh then you could use an opto detector to detect the LED pulsing and use that as your input to the coin "mechanism"

 

[westie101]

There is no pulsed output terminal on modern meters so it would require some fairly major work to find one which could affect the meter calibration seals.

I very much doubt British Gas would allow that level of modification

 

[JohnW2]

If the new meter has the LED that pulses at ( I think ) one pulse every 0.1 Kwh then you could use an opto detector to detect the LED pulsing and use that as your input to the coin "mechanism"

I think they usually flash every 0.001 kWh - but I agree that your idea would be a good one, provided one could get reliabilty of pulse detection across a wide range of ambient lighting conditions.

Kind Regards, John.

 

[RMIM]

If the new meter has the LED that pulses at ( I think ) one pulse every 0.1 Kwh then you could use an opto detector to detect the LED pulsing and use that as your input to the coin "mechanism"

thanks for the reply bernardgreen
Yes I think that is a good idea - I had this idea but did not want to go to the hassle of doing this if the meter already had a nice clean pulse out signal - also what stops people pulling the thing off the led window.

I think I might have to use this idea in the end though, would be cheaper - what would the electric man say seeing something stuck on his meter?

 

[RMIM]

There is no pulsed output terminal on modern meters so it would require some fairly major work to find one which could affect the meter calibration seals.

I very much doubt British Gas would allow that level of modification

http://www.stephenpwales.co.uk/Product/single_phase/home_single phase.htm

look at the second one. it has pulse output for pc. Im sure the one I have at home does too as I see 2 grommets near the live wire. Look at the data sheet for that model, is that not where the pulse output is?

 

[flameport]

In reality, you can't use the suppliers meter, since even if it does have a pulse output and for some unlikely reason they allowed you to connect to it, the meter could be changed for a different model at any time.

Just buy a suitable meter with pulse output, and have it installed immediately after the suppliers meter.

 

[westie101]

As for the seals any lead or steel sealing pliers in use by DNOs or suppliers are registered to an individual, so it would be unlikely that an electrician would have a set.

 

[RMIM]

In reality, you can't use the suppliers meter, since even if it does have a pulse output and for some unlikely reason they allowed you to connect to it, the meter could be changed for a different model at any time.

Just buy a suitable meter with pulse output, and have it installed immediately after the suppliers meter.

Thanks for the reply flameport.

Just seems a waste as the output is already there (i think). Lucky it's only about 50quid for a new meter - a lot cheaper than some of the coin meters I have bought in the past.

 

[RMIM]

As for the seals any lead or steel sealing pliers in use by DNOs or suppliers are registered to an individual, so it would be unlikely that an electrician would have a set.

I see - thanks for the help westie.

 

[RMIM]

looks like the photo diode method would be cheaper.

what would an electric meter guy make of such a device stuck to his meter?

 

[bernardgreen]

You put the photo diode on the end of an shaped arm that is fixed to the board so nothing is attached to the meter itself.

You may have to debounce the signal from the photo diode.

It is not impossible that the LED visible pulses are each a series of rapid pulses.

 

[RMIM]

You put the photo diode on the end of an shaped arm that is fixed to the board so nothing is attached to the meter itself.

You may have to debounce the signal from the photo diode.

It is not impossible that the LED visible pulses are each a series of rapid pulses.

Thanks for the reply bernardgreen.

I would have preferred to actually stick in on the led window, so the photo diode only received signals from the meter. I could try your method but it would take some tuning I'm guessing to get it to react to the led pulse only and not the light when I open the electric cupboard door - I guess I have to read up on these detecting circuits. I'm guessing there are certain frequencies that only the led will emit and I have to find a matching photo diode?

It's a great solution for my personal needs at home if I wished to monitor my electric, but as a solution for a landlord with dodgy tenants, it's too easy to block the monitor and receive free electric!

 

[JohnW2]

I would have preferred to actually stick in on the led window, so the photo diode only received signals from the meter. I could try your method but it would take some tuning I'm guessing to get it to react to the led pulse only and not the light when I open the electric cupboard door - I guess I have to read up on these detecting circuits. I'm guessing there are certain frequencies that only the led will emit and I have to find a matching photo diode?

Coloured LEDs will emit light over a restricted range of frequencies but the problem, of course, is that white light contains all frequencies of visible light, so you could have a bit of a problem unless the photodiode is so close to the LED that the LED light swamps everything else (i.e. you can adjust your system to low sensitivity)

It's a great solution for my personal needs at home if I wished to monitor my electric, but as a solution for a landlord with dodgy tenants, it's too easy to block the monitor and receive free electric!

As you say, it's a great idea, but I would think far too easily interferred with by dodgy tenants, if that's what you're dealing with. I suppose you could also install a kWh meter in their supply (without pulse output), so that you could ascertain whether they had been tampering.Edit: wasn't thinking straight here - you already have the meter which will provide that confirmation!

What was wrong with the 'pulse for PC' meter you found? - that looked like an ideal solution for you, and very much harder to tamper with. Edit: ... and you could, of course put such a meter after the 'real' one.

Kind Regards, John.

 

[ban-all-sheds]

Err....

Landlord...

Reselling electricity to tenants...

DIY metering...

DIY coin mechanism...

I don't think so.