Optical Utility Meter LED Pulse Sensor to use in Malta

Hi I live in Malta and I intend purchasing an emonPi Solar PV unit to monitor power taken from grid as well as that generated by my panel array. I wish to include the Optical Utility Meter LED Pulse Sensor but am not sure if the sensor can be attached to our meters since the Pulse window is in an awkward location.
Any help would be welcome.

Welcome, Henri, to OEM.

Am I right to think that you have single phase 230 V mains electricity?

Firstly, the optical pulse sensor will not be useful on your main grid meter, because even if the meter pulses when exporting, it cannot differentiate between importing and exporting.
Second, the pulse sensor is very good for counting up energy, but not very good at measuring power - because that’s the rate at which pulses arrive, and you only know that after each pulse.
And finally - you can have only one pulse sensor attached to an emonPi.

Can you provide a photograph of the generation meter? If it helps, the pulse sensor is approx. 22 mm in diameter and 20 mm deep, but you need 30 mm from the centre for the cable to bend, and enough depth to be able to see to position it accurately over the LED, so about 50 mm even when using a very small mirror to align it.

Why don’t you want to use a current transformer for both meters? That’s why the emonPi has two inputs for c.t’s.

Hi Robert

I confirm that the nominal voltage is 230V but I have over the past few months seen voltages in excess of 250. This is one of the reasons that I have been looking for some form of monitoring of my energy use.

I also have an array of 16 PV panels on my roof and the financial return has been abysmal. This past summer I attended the Fully Charged Live Show at Silverstone where I found your stand and eventually your products and services and after reading the specs I have settled for the emonPi with Solar PV bundle because I need to verify whether my consumption is being metered accurately. I also found out during this visit that the utility provider has been applying the feed-in tariff in a manner that benefits them and we have lost thousands of Euros over the past six years.

Our provider actually adds what we take from the grid to the full amount we generate (we have a second meter) then subtracts what we export and bills us in full for the total amount used from the grid AND from our own panels (we pay an exorbitant tariff). I know that at least one UK provider does not calculate the bill in this method as I then went on the FullyCharged forum and one patreon responded with confirmation as to how they are billed by their provider and it is definitely not in any shape. form or manner like ours. I have calculated how much the different methods work out and the result was eye watering, I should have received the princely sum of €1600 over the year and NOT be out of pocket by €1200 for the same period. This means that I effectively made a loss of €2800.

In order that I may take some form of legal action on the various issues I have I need to have in hand proof of the over-voltage condition I am experiencing, a check into whether the meter is accurate or not as one of the bills showed a huge spike from an average consumption of around 24 units/day to over 70 units/day which the provider brushed off since the readings were accurate but consumption immediately went back to normal. The third and last issue, that of the method of billing, it would be highly appreciated if you have any contacts in the industry that might be in a position to indicate how the EU expects the Feed-in Tariff Scheme to be implemented as I am sure our provider is not following the spirit of the scheme.

To go back to the Pulse sensor I have attached a file with two images of my meter, Image ‘A’ indicates two windows, window marked A has two LEDs that flash, one much slower than the other. Window marked B does not flash but I have seen inspectors use this point to connect to their handheld reader to take off information. Image ‘B’ is a close-up of the two LEDs, the top is marked Ra the bottom one Rr, I assume that one is for Wh whilst the other is for KWh, although the frequency between the two seems to be random. I am certain that you will confirm that the sensor cannot be attached to the meter since it uses two LEDs and that the surface around the LEDs is not flat anyway.

As you point out only one sensor can be attached to the emonPi and in effect that is what I was planning, to use the two CTs for the two meters, one consumption the other generated.

If you confirm that the LED Pulse Sensor cannot be attached to the meter then I shall go ahead and order the emonPi - Solar PV Bundle and since I have another two properties, plus another of my son, if this one works as I expect then there will definitely be more orders to come.

I look forward to your response and any help you might be able to offer with respect to the Feed-in Tariff issue.



Is yours a 3-phase supply? It looks as if there’s a linked 3-pole switch is part of the meter and three fuses below.

If that’s the case, your needs are a lot more complicated than an emonPi can meet.

The purpose of that is fairly clear - it’s probably a bi-directional IR link (i.e. both transmitter and receiver) and the two devices are most likely exchanging encrypted data. So it’s unlikely to be usable.

I don’t go along with that, my bet is “Ra” is Active and “Rr” is Reactive energy - Wh & VARh.
Is the calibration of those not shown on the front of the meter? I can read one of them “Ra = 1000 imp/kWh”

That raises the question - do you pay for active energy (kWh) only, or is there a penalty/excess for consuming reactive energy (VARs)? That might explain the sudden jump you saw.

The method of fixing for the sensor is a sticky pad that affixes to the meter, in the centre is a small hole that must be positioned over the LED. The front surface of the pad is a forest of short plastic pins with rounded heads, a similar pad is fixed to the sensor. When pressed together, the pins interlock (but can be separated again relatively easily). So if there’s enough area to get the pad on and be reasonably flat - possibly convex but maybe not concave, and you can see the LED through the hole, it stands a chance of working.

If you’re likely to be challenging the accuracy of the meter, then I think it is clear that counting the pulses that the meter emits won’t help you, as all it will do is confirm the number the meter itself displays. I would advise using two c.t’s in any case.

In terms of the feed-in tariff, I obviously can’t comment about your supplier, or indeed standard practice in Malta, and there are others here who know the details and can tell you precisely how it works. FIT is no longer available for new installations in the UK.

You should see this:
Stakeholder Information - Association of Meter Operators and look at “Reverse Running Meters Guidance”
and in particular the first document “Reverse Running Meters Guidance”.

The over-voltage should not affect the accuracy of the meter. It means that some of your appliances will run at a higher power than expected, and some may be damaged, or have their life shortened, as a result. That is entirely separate from the method of billing. As Malta is in the EU, I think the voltage upper limit will be 230 V + 10%, i.e. 253 V. If it is consistently above that (and you must carefully check the calibration of your emonPi if you are going to rely on it) and you can show a loss as a result, then you can probably claim compensation. But your electricity supplier could easily claim that the readings are meaningless. If so, you might need to hire a mains analyser & recorder that comes with certified calibration. Evidence from that would be a lot harder to dismiss.

No I’m on single phase. As my home is part of a block we obviously have a three phase incomer and the supply is then divided between the home owners.

Hi Robert

A couple of last questions before I confirm my order. Can you give me the length of the cables of the CTs as I plan to install the emonPi away from the meter as this space is accessible by other property owners and I have a room just behind the meters that I can use to set up the unit, but this obviously needs the cables of the CTs to have some length.

Since I intend installing a second unit within the same complex for another property I need to know whether the Emoncms app on one mobile, tablet or PC can access information of more than one system, I am hoping to have three units for three different properties in total.

Please confirm whether it might be possible to install the LED pulse sensor on my meter with the information I sent or whether you need any further information so that I can finalise the order.



The c.t. cables themselves are approx. 1 m long and terminate in a moulded-on plug that is fractionally less than 10 mm in diameter. You can extend the cable - details are here: Learn→Electricity Monitoring→CT Sensors→Extending CT Sensor Cable→Extending the Current Transformer Cable

The second “unit” will probably be an emonTx. Your emonPi will receive the data from that - provided it can receive the 433 MHz signal through the building - and will be able to store and display the data in exactly the same way.

I cannot do that with the photographs that you sent - I cannot see the contours of the front of the meter and I have no idea of the scale. My best suggestion is for you to take a coin or similar that is as close as possible to the size of the sensor, and see for yourself if there is a flat or nearly flat surface where it fits directly in front of the Ra LED.

Good morning Robert

Firstly I thank you for your response. If I am understanding correctly with the emonTx it is possible to set up the dashboard to have different graphs for the two properties by setting the CT readings accordingly. My original question is still valid for the third property that is on a different island, which means that this would require a separate emonPi, so can I have the third property set up on the same dashboard through one account or is it possible to set up the third unit on a different account and access it from one iteration of emoncms by logging in to the different accounts?

Although the emonTx solves one problem it does create another issue as one of the two adjoining properties will eventually be used by my other son who would definitely want to be able to monitor his energy use and as the readings of the two meters would be uploaded to one account would it be possible for him to access the same account and set up his dashboard accordingly?

I have also checked whether the LED sensor can be physically mounted on the meter and because of the contours around the LED this would be rather difficult to mount flat and will leave a gap in nearly the bottom half of the sensor of nearly 3mm so am not sure whether it will work or not. I will purchase the sensor anyway and see how it goes.

Finally I was about to confirm my first order and noticed that restocking is underway and that you will not be able to mail them before the 24th. I am bringing this up as I intend sending the package to a relative in England who will be travelling to Malta on the 1st of November so the package would have to be with them by the 31st October at the latest, do you think the package has a good chance of arriving or not if I use ‘special delivery’?

Thanks again for all your support.



You will need to ask that question at the shop: [email protected]
If you explain what you intend, they will be able to advise you.

Regarding emonCMS, I am not an expert, so I cannot really answer whether it can do what you want.
@pb66 - Can you help here please?

Thanks Robert