DL69-2048 Multi-functional Digital-Display Meter

[Edwin Croissant]

I ordered a DL69-2048 through Aliexpress for about 14 euros including shipping. Arrived after 12 days.

This meter can measure voltage, current, real power, VA, and cosφ. (80-300V and 0-100A) and it will show real power, voltage and amps together in one display.

I checked the meter with an ELV Energy Master Profi 2. According to a review by the German magazine C'T (number 21-2013) this meter had no deviation with their reference device LMG95 with a basic accuracy of 0, 03%.

The voltage reading is 0.5% low.
The current was at first 3% low and after 5 minutes the meter stopped measuring current. There was a bad solder joint in the current transformer. I fixed that and with 4 additional windings on the secondary side of the current transformer the reading was now within 0.5%. The panel meter is well made so I presume I had some bad luck with the current transformer.

I tested the meter with a 2000W wallpaper stripper, a 150W soldering iron with a dimmer and a vacuum cleaner. The deviation was usually more as seen in the picture (this was a lucky shot) but not shockingly different. The problem with these measurements is that my voltage varies continuously a tiny bit and the meters have different update rates.

The readout of the meter switches automatically from 9999.9 W to 10000 W. (I checked , not with a 10kW load but with 10 primary windings so the meter see a 10 x higher current)

The instructions state that the meter is only suitable for 50Hz but the vendor confirmed that this is an error in the instructions and that the meter can also be used for 60Hz. I have seen instructions on the internet that this meter is suitable for both 50 and 60 Hz. I can't test it at 60 Hz so your mileage may vary.

The meter must be wired between the power supply and controller, placement between the controller and heater will probably destroy the meter.

I hope this is useful for somebody

[skow69]

Why would putting it between the controller and heater harm the meter?

[Edwin Croissant]

The 300V type needs at least 80V to operate properly according to the manual. I opened it up and it looks really well made inside. The internal power supply is is very basic, the internal voltage regulator is hooked to the mains through a capacitor. It's own power consumption is only 0.6 W with a power factor near zero. I expect that feeding this basic power supply with a chopped up output from a triac dimmer circuit will damage the capacitor.

The drawback of measuring the mains voltage instead of the load voltage with a triac dimmer is that the displayed power factor is wrong. But I am not interested in the power factor, I want to know the true power to the heating element. And that is what this meter displays.

[skow69]

I see. Thanks, Edwin.

[carbohydratesn]

Very neat, that looks like a great little display! I might get one myself

I'm only a little familiar with how these kinds of meters work, and it's been a few years since my last electrical physics class - do you think it would be possible to wrap *two* lines into the inductor, to measure the combined wattage of two elements? One with a controller between the display and the element, and the other wired directly to the line.

I think it should still measure that correctly, and if so, that would seal the deal for me. It would be able to show the true wattage of my boiler, with either one or both elements plugged in, without having to change the wiring at all for different circumstances.

Thanks for sharing!

[googe]

Thanks for posting this Edwin!, was looking at this very thing on Ali lastnight and thought why aren't people using this, looks good!, just presumed like other things that do multi tasked are often crap, sounds ok by what you said!, not that I really understand what you said lol. Any chance of dumbing it down for simple folk.like me... Does it measure power from the direct supply? And not at the element?. Don't really understand how that works!.

[skow69]

$15.12 delivered and the donut is included. Mine is on order. Thanks for the tip, Edwin.

Actually, without modification, All it will give you accurately is amperage. Because of the 80 volt minimum requirement, that Edwin mentioned, you can't connect it between the controller and element. It has to connect to 120 ahead of the controller, so it will measure the input voltage instead of output. That means the power meter (watts) will be off too. I'm thinking, for 15 bucks, I'll run 1 more wire into it for the power supply, and isolate that from the sensing ckt, which will connect to the output. I'll let you know if it works.

Not recommended for anyone without previous experience and appropriate tools.

[skow69]

Or maybe not. Ali won't submit order. I'll try later.

[Jacksonbrown]

Does it have an output signal?
I want to measure real power to my element for my new arduino controller, will this be of use?

[Edwin Croissant]

The drawback of measuring the mains voltage instead of the load voltage with a triac dimmer is that the displayed power factor is wrong.

Oops, this is so wrong Power factor is defined as real power divided by apearent power or P/VA. So those readings are correct. How did I make this mistake, simple, 45 years ago this subject was explained in school with the phase shift caused by inductive and capacitive loads as triacs were invented just couple years earlier and not in wide use at that moment. The phase shift was the part that got stuck in my mind. So I thought that with a triac control and a resistive load there is no phase shift so the power factor should always be 1. Stupid me I'm sorry for the confusion I caused.

googe, this meter measure the power directly from the supply, connect the green terminals to the mains, slide the donut over one of the wires to your controller and connect the donut to the blue terminals. Please note that your heating element will receive a little bit less power then displayed due to the voltage drop of 1 to 2 volts over the triac.

scow69, my understanding is that this meter works by sampling the current and voltage many thousand times a second and compute the real power from these values. So the Watt reading must be the real thing. When my 10000W SCR with digital control arrives (any day now) I will check by heating some water and check the temperature increase.

carbohydratesn, if your heating elements are connected to the same phase the meter will add the currents together so this should work.

Jacksonbrown, this meter has no interface, but according to the DIY wattmeter with an Arduino and the Openenergymonitor project simply hook up a current and voltage transformer to the Arduino and let the Arduino do the work for you

Next is to figure out how to interface the 10000W SCR with a Arduino (two opto couplers should do it I think), measure the heat transfer coefficient of the shiny 12 mm csst I purchased and see if i can use a heater control valve for a Ford Ka as dephlegmator control valve. I'am busy

[skow69]

Consider this. I have a 120 volt 1500 watt element. When I dial it down to half power the controller sees Vin=120, Vout=85, I=8.9 amps. If I calculate power as Vout*I, the result is 757 watts. But the DL69 can only see Vin so it would calculate the power as 120*8.9=1068 watts.

I'm not questioning the sampling rate, I'm saying that having the sensing ckt married to the power supply, which requires 80 VAC minimum, limits its utility for monitoring an application where we want to modulate the voltage applied to the load, sometimes to very low levels. The simplest patch would seem to be to isolate the power supply, feed it from Vin, and let the sensing ckt read Vout.

The power factor really doesn't matter to me, but I do think it is important to measure the controller output voltage.

[Edwin Croissant]

I connected a soldering iron with a dimmer and adjusted the voltage across the element to 120 V TRMS (Brymen BM869S). Mains was 218V, Amps 0,39A power reading was 52 Watt and apparent power reading was 85 VA. 120V and 0,39 A is ~47W. 218 V and 0,39A is ~85 VA. Another measurement: 153V across the element with a current of 0.5 A give a reading of 81W and 110 VA. So this meter give you the real thing. It deviate 5W but the power it measure is including the power dissipated by the regulator.

To give a more precise explanation, this meter chops 0,5 second (in my case 25 full cycles) into thousands of time slices, measure for each slice the voltage and current and calculates the transferred energy within that time slice. These energy readings are aggregated and the value is multiplied by 2 to give the Watt reading.

I think is is possible to get access to the voltage sense connection. R3, R4 and R5 are 1M and connected in series and with R6 of 1k the combination is a voltage divider. R3 is connected to one of the mains connections. Cut the trace that runs under C1 and that is your sense connection.

The only bennefit is that you can measure the power of the heating element without the power dissipated by the controller. I dont think that this is worth the trouble.

[Kegg_jam]

Ok, so I am following this with interest.

Even if you were able to un-marry the power supply from the measurement point would it be able to measure true RMS? The whole problem with that cheap blue meter from Jimbo's thread was just that. Not true RMS.

I think the power factor is important. As Skows equation above doesn't take that into account and from his math it would indicate his controller would be dissipating 300 watts which just isn't the case.

I'm inclined to believe that if you changed the Voltage measurement to the controller side then the power equation would be out of whack.

[Edwin Croissant]

Kegg_jam, I can confirm that this meter is true RMS, I checked this with my Brymen BM869S. I think the cheaper meters, that just measure voltage or current, measure the average and are calibrated to show the RMS value for an undistorted sinus. I can also confirm that it also measure true power. Even with the chopped up current from a phase angle dimmer control. So there is no need for an extra sense connection. As it's load is both heating element and controller it will also measure the power loss in the controller which is between the 1 to 2 V. But at 220 V that is about 1% extra.

Jimbo's thread is an interesting one, it also mentioned the SCR that I ordered. Got a little bit worried but at the end someone confirmed that it will work at 50Hz. Hope to find out soon

[skow69]

OK. I don't understand how it works, but I am convinced.

That is a very smart meter for 15 bucks.

[googe]

Thanks Edwin!.

[Kegg_jam]

Yes, good work Edwin.

[White_Lightning_Rod]

Quick question on this. Ill be hooking up to 240v two phase. Im guessing I will need to run a lead from 1 side of the green terminal to 1 of the hot wires on each phase. So green terminal left to hot1 and green terminal right to hot2? I have the 10000w scr from fleabay with a dual pole switch before the scr and of course the element after it. So this meter will be connected between the switch and the SCR. Does that sound correct?

[Edwin Croissant]

Quick question on this. Ill be hooking up to 240v two phase. Im guessing I will need to run a lead from 1 side of the green terminal to 1 of the hot wires on each phase. So green terminal left to hot1 and green terminal right to hot2? I have the 10000w scr from fleabay with a dual pole switch before the scr and of course the element after it. So this meter will be connected between the switch and the SCR. Does that sound correct?

Yes, that sound correct to me, The meter must be connected between the switch and the SCR.

Edwin

[White_Lightning_Rod]

Edwin thanks for posting this. I got mine hooked up and Im no electro physicist but I think I understand what the active power, and power factor are, do you care to explain what apparent power is. My understanding is active power translates to basically wattage for instance my element is 4500w and with my controller on full tilt (18amps) the active power is 4265w not the full 4500 because of the drop from 240v to 236v because of the voltage used by the contoller. The power factor at the same setting is 1.0 which means 100% of what the curcuit is capable of. As i turn the knob down when the power factor is at .50 or 50% my active power is a little below 2250w. With all that said in practical terms what is "apparent power" which on this meter is abreviated as Va?

[Edwin Croissant]

Edwin thanks for posting this. I got mine hooked up and Im no electro physicist but I think I understand what the active power, and power factor are, do you care to explain what apparent power is. My understanding is active power translates to basically wattage for instance my element is 4500w and with my controller on full tilt (18amps) the active power is 4265w not the full 4500 because of the drop from 240v to 236v because of the voltage used by the contoller. The power factor at the same setting is 1.0 which means 100% of what the curcuit is capable of. As i turn the knob down when the power factor is at .50 or 50% my active power is a little below 2250w. With all that said in practical terms what is "apparent power" which on this meter is abreviated as Va?

With alternating current the real dissipated power (turned into heat etc.) is depending on the phase shift between the current and the voltage and the shape of the waveform of the current and voltage. Measure the voltage across a SCR and the current flowing through and it appears that the SCR is dissipating a lot of power. In reality when the SCR is not conducting there is voltage but no current, and when the SCR is conducting there is current but no voltage. So no real power is dissipated in the SCR. That why it is called apparent power. You can only multiply current and voltage which each other tho get the real power if the load is a resistor. The power factor is defined as the ratio of the real power and the apparent power.

[skow69]

Excellent explanation. Thank you.

[White_Lightning_Rod]

I agree with Skow, great explanation, thanks.

One more question would it affect accuracy or be somewhat counterproductive if you were to connect the voltage circuit as we have established, before the controller, and then put the current transformer donut on one of the hot legs after the SCR controller. This way you would be measuring the supply voltage, but the current measured will be the actual current being sent to the element.

[Edwin Croissant]

I agree with Skow, great explanation, thanks.

One more question would it affect accuracy or be somewhat counterproductive if you were to connect the voltage circuit as we have established, before the controller, and then put the current transformer donut on one of the hot legs after the SCR controller. This way you would be measuring the supply voltage, but the current measured will be the actual current being sent to the element.

That depends on how the SCR works, many are simply connected in series with the load, in that case it doesn't matter. If you got a SCR like the 10000W one with a build in fan it does matter a little bit as the fan consumes a couple of Watts. Compared to the kiloWatts from the load those are peanuts.

[Anthoney]

This is the cheapest true RMS meter I have ever heard of. Great find.

[Edwin Croissant]

This is the cheapest true RMS meter I have ever heard of. Great find.

The Hiking dds238-2 sw is a little bit more expensive. I ordered one for a completely different reason. It's a energy meter so it's measure kWh and it is DIN rail mountable. It can also measure Volts, Amps, frequency and real power. It's made for billing purposes and I found that it is very accurate. It also got an open collector output which give 1600 short pulses for each kWh. Connect it to an Arduino, measure the time between pulses and the power is 2250 / (time between pulses). I tested this meter some more and found that it is very accurate. The only drawback I find is that the meter displays kWh when switched on and that the button must be pressed 7 times to get the power reading.

[Anthoney]

You had to modify the current transducer a bit to calibrate it though. I don't have a reference source to calibrate from.

[Edwin Croissant]

I have tested the DL69-2048 and the Peacefair PZEM-006 with a 10000W Digital controlled SCR on a 2kW wall paper stripper. The ELV Energy master was used as reference.

I also measured the voltage across the heating element and the current through the heating element with a Brymen true RMS meter and a vintage end seventies Data Precision Model 175. To measure the current with the Data Precision I used a 20A to 200 mV shunt. The Model 175 does not measure True RMS, it measures probably an average and is calibrated to give the effective voltage or current. Two passes were needed to measure the power with the DMM's, One pass for the voltage and another pass for the current.
My line voltage varies all the time so the results are not very accurate. The readings of the Brymen are lower as the Brymen measures the power of the load only while the power meters measure both the load and the losses in the SCR. Interesting is the Model 175's considerable error. At ~50% real power the Model 175 shows only ~25%.

The DL69 is nicely build. The LCD of the Peacefair is protected by a easily punctured soft plastic screen. The Peacefair is sometimes slow and can be 2 seconds behind a change in power setting. Sometimes the Peacefair dos not register a load under 10% of the full load.

Do not connect these power meters to the output of the SCR, this will destroy these kind of meters. These meters need a clean undistorted sine-wave for their power supply.

About the SCR:

First of all, this one will only work on 50Hz. I checked by feeding the control unit with 60 Hz. Won't work. I can't find a hidden menu or connections to reprogram this thing.

The Triac is 1200V 100A (BTA100-1200B) complete with a snubber circuit. Going from zero to max takes 10 seconds. The other way around takes also 10 seconds. It goes up and down with one continuous speed. The unit work well and the setting is repeatable.

Voltage drop across the SCR when it is fully conducting is about 1 Volt. The unit becomes hardly warm with a 1800W load.

It is advised to take the PCB and the Triac from the heatsink to remove the cutting oil used during the milling and drilling and to apply fresh thermo paste.

It is also advised to make sure that the neutral is connected on the outside terminal on the PCB (the bue wire on the photo) , one of the traces has a 1 mm clearance with the mounting stud on the heatsink, maybe it is better to replace this trace with an isolated wire routed well away from the mounting stud. Or replace the metal studs with plastic one's. Please note that I have seen two versions, the difference is the way the PCB is mounted on the heatsink. There are left and right handed heatsinks.

When the input and output is swapped the unit still seems to work. With no load the display goes dim and with a load the display goes dark when set to zero (do not ask me how I know this). Prolonged use in this condition will probably destroy the 5V power supply on the unit.

There is a zero crossing circuit and the unit works by delaying the start signal to the Triac. Some effort has been made to linearize the unit as can be seen on the power curve and the duty cycle curve of the control signal to the Triac. The signal to the Triac is a 100Hz square wave with a varying duty cycle synchronized on the falling edge of the zero crossing signal.

The unit remembers the last setting after disconnection.

[bearriver]

Nice post Edwin. I own two of those digital scr controllers, the same ones exactly. If somebody wants them I would be happy to send them off to a new home. Won't work for my purposes...

I appreciate the review. I need to replace a meter and the DL69 looks perfect.

[Anthoney]

Great work Edwin. I do like graphs.

In the power meter test most of the meters seemed to fall pretty close to each other for most of the curve. Apart from the obvious one you pointed out. Other than that the red line seemed to deviate the most. Is that one a bit off? Or is that best reference and the others are a bit off? I realise it's not by much. Just curious.

If buying from scratch I think I would take the DL69 over the peacefair but it will do for now.