Voltmeter/Ammeter Put the smoke back

[Hound Dog]

Well did some stripping runs yesterday and a spirit run today. Near the end of the spirit run I noticed one of my meters was off. I opened the box to take a peek and saw the smoke had escaped from one of them and the other one was looking the same so it is not far behind.

It is the DROK® AC 80-300V/50A 110V 220V Digital LED Amp Volt Meter Ammeter Voltmeter Gauge+Current Sense transformer sold on Amazon. Don't really know what's wrong here. I ordered two more and will see if they hold up.

Where they burned:

When I get the new ones I will make sure the wire to that transistor is pushed away from the connector in case it gets that hot again.

[bearriver]

Interesting that your transformer looks different than mine, from the same manufacturer.

That's unfortunate. Mine has been working as intended so far...

[cranky]

Just wondering Hound Dog, how many runs did you have on it and how long was it under a load and how much power were you using? Just curious about the failure. I've been running my controller what I think is pretty hard lately and just had a look at it. At a glance it looks just like yours but the wire that burnt on yours is much further away from the connector on mine. I don't know the brand of mine but this is the one I bought
http://www.amazon.com/gp/product/B00G9Y ... CZ8CRWX2GH" onclick="window.open(this.href);return false;" rel="nofollow

[bellybuster]

Seems to be hit and miss whether these meters will work with a clipped sin wave. I got lucky with mine, almost 2 years on it

[Drunk-N-Smurf]

Looks like something with that plug is arcing out since the damage is centred around that corner of the connector.

.....strange

[john2674]

I had both of my drok meters fry on my new controller within a few minutes of firing them up. I had tried to wire mine so the meter read the change in voltage on the ...out... side of my ssvrs.
I ordered 2 more and wired them so the volt meter is just reading input voltage and so far no problems yet.. only have about 7 stripping runs on it so far though.
don't know if this has anything to do with your problem ,but I figured I would add it since they are the same meters.

[Hound Dog]

Just wondering Hound Dog, how many runs did you have on it and how long was it under a load and how much power were you using? Just curious about the failure. I've been running my controller what I think is pretty hard lately and just had a look at it. At a glance it looks just like yours but the wire that burnt on yours is much further away from the connector on mine. I don't know the brand of mine but this is the one I bought
http://www.amazon.com/gp/product/B00G9Y ... CZ8CRWX2GH" onclick="window.open(this.href);return false;" rel="nofollow

Same meter but the 50 amp version. I have only done a few cleaning runs, two boilers of stripping runs then this one spirit run. Now this spirit run was a bit longer as it involved playing with settings to see what Temps I pulled at different power settings. Nowhere near as long as a 2" column run though. It is a Drok meter.

[NZChris]

Mine looks like it is out of the same factory.

230V here in NZ.

It hasn't done many runs, but I had a look today and it looks fine.

[heyhaychapman]

HD looks to me like you have put a multi core flex through the Current Transformer? If so that should just be the live cable only.
http://www.electronics-tutorials.ws/tra ... ormer.html

[Edwin Croissant]

The internal power supply of these meters is based on a serial capacitor (the big red thing on the left) a diode bridge (the tiny black ic with 4 connections), a couple of resistors, a zenerdiode and a low voltage capacitor. This works as long as the supply voltage is a nice sine wave. Connect this supply to the output of a SCR and the sharp rise time that occurs when the triac is fired result in a high current spike through the capacitor. It looks that the resistor next to the connector is dissipating this power and overheats. After some time the capacitor will fail to.

You might consider the DL69-2048 as this meter is capable to measure true power and can be connected before the SCR. The Hiking dds238-2 sw is another alternative, I ordered one 10 days ago, will test and report.

Unrelated to this topic this type of power supply is frequently used in coffee machines, refrigerators etc. The capacitor used in this type of equipment is often underrated for the working voltage. After a couple of years in service these capacitors lose their capacitance resulting in erratic behavior of the coffee machine, fridge light blinking etc. Replace the capacitor by a higher voltage one will fix the problem for good. Surprisingly there is often enough room on the circuit board to accommodate the bigger capacitor, it is as if the engineer designed for the proper one but the purchase department tried to save a few cents and bought the cheaper, smaller, lower voltage alternative.

[cranky]

Connect this supply to the output of a SCR and the sharp rise time that occurs when the triac is fired result in a high current spike through the capacitor. It looks that the resistor next to the connector is dissipating this power and overheats. After some time the capacitor will fail to.

I'm using an SSR which is controlled by a 500k OHM potentiometer, no triac involved. I believe Hound Dog is using the same setup. My wire to the meter comes off the output side of the SSR, are you saying I need to move that to the input side or since it is an SSR instead of a SCR (I don't know the difference to be honest) or is it ok since it is solid state and no triac is involved?

I did find a picture of the back of my meter

If you look close you can see the wire that burnt on Hound Dog's is much further away from the connector.

[NZChris]

Power to mine is from the input, and it is measuring the input. Working well so far.

[Edwin Croissant]

I'm using an SSR which is controlled by a 500k OHM potentiometer, no triac involved.

The triac is the part of the SSR that does the hard work. So if you do not want to blow up your meter you better move the connections to the input side of your SSR.

[Hound Dog]

I'm using an SSR which is controlled by a 500k OHM potentiometer, no triac involved.

The triac is the part of the SSR that does the hard work. So if you do not want to blow up your meter you better move the connections to the input side of your SSR.

I am running the exact same setup as Cranky. If the connection is moved to the input side of the SSR, will it not just always read my maximum voltage being fed and not the cut voltage actually going to the heating element? I already know I have 237 volts feeding in. If I don't know the voltage and amperage output going to the element how do I determine the wattage?

HD looks to me like you have put a multi core flex through the Current Transformer? If so that should just be the live cable only.
http://www.electronics-tutorials.ws/tra ... ormer.html

This is a 10 gauge hot leg running through the doughnut. Actually the output leg from the SSR.

[Hound Dog]

OK, went out for a ride and thought about this a bit.

Edwin, I read your post on the DL69-2048 meter you suggest and while I know you tried to dummy it down, you didn't dummy quite enough for me Sorry. I am trying hard to understand how you are getting the wattage by measuring the input side and the amperage. Does that other meter just hook up to the input side and sense the circuit being used? I have basic construction electrical knowledge. You know, I can wire some plugs and switches, perhaps wire up a water heater and install a new breaker without frying myself. All those are pre set up systems though.

Cranky, yep, the wire on the capacitor on yours is turned and not touching the connector like it is on mine. Looking at Edwin's post for the DL69-2048 he and Skow were talking about it being rated for 80V. This had me thinking. This meter is rated for a minimum of 80v also. I have two burners. The one that burned up is the one for the top. Why? Well perhaps because I don't have a cut off switch. I was just turning the potentiometer down all the way. That left it reading like 38v while I used the lower burner. The lower burner meter is burned in the same spot but still working. Perhaps because I turn it down when messing with things but usually have it turned up. Cranky, on yours you have only one burner. You probably always have more than 100v coming out of your SSR therefore being in the operating range of the meter and not burning it up. Perhaps I should really put a switch on mine to turn it off proper before trying to run it again and watch to make sure I don't run a burner below 80v.

That and perhaps listen better to what Edwin is saying and rewire appropriately

[NZChris]

W = V x I

If I could buy a gadget that I could dial to get more watts out than was going in, I'd buy a dozen of them

In theory, you can calculate the watts from either side. The only difference, for us, would be the small amount lost to heat by the SSR, but bugger the theory, I chose the input side, because it hasn't been mucked around with by whatever magic the SSR does.

BTW, the voltage where I am is not stable and can vary 10v during a run.

[cranky]

Cranky, yep, the wire on the capacitor on yours is turned and not touching the connector like it is on mine. Looking at Edwin's post for the DL69-2048 he and Skow were talking about it being rated for 80V. This had me thinking. This meter is rated for a minimum of 80v also. I have two burners. The one that burned up is the one for the top. Why? Well perhaps because I don't have a cut off switch. I was just turning the potentiometer down all the way. That left it reading like 38v while I used the lower burner. The lower burner meter is burned in the same spot but still working. Perhaps because I turn it down when messing with things but usually have it turned up. Cranky, on yours you have only one burner. You probably always have more than 100v coming out of your SSR therefore being in the operating range of the meter and not burning it up. Perhaps I should really put a switch on mine to turn it off proper before trying to run it again and watch to make sure I don't run a burner below 80v.

That and perhaps listen better to what Edwin is saying and rewire appropriately

You might be right about that. I noticed the controller still having some power when I added the meter. but the main reason I added a switch was the unregulated hot wire. The switch is just a little safety. I took a close look at mine and there is no sign of it getting hot. I'm debating switching the wires around because my interest is peeked. I've always considered buying another meeter and SSR and mounting them in the box as hot spares so I have backups in case of failures. I already have that with the potentiometer. I'm not really sure how much voltage I run it was pretty low on the little pot when I ran the rice the other week, I want to say I was running at an indicated 80V but didn't keep any notes so it may have been higher. Like you Hound Dog my electrical understanding is pretty basic and appreciate the input from the electrical guys.

[Hound Dog]

W = V x I

If I could buy a gadget that I could dial to get more watts out than was going in, I'd buy a dozen of them

In theory, you can calculate the watts from either side. The only difference, for us, would be the small amount lost to heat by the SSR, but bugger the theory, I chose the input side, because it hasn't been mucked around with by whatever magic the SSR does.

BTW, the voltage where I am is not stable and can vary 10v during a run.

Yes NZC, my voltage fluctuates a bit too. But, when using the volts x amps = watts equasion, measuring the volts on the input side is always close to 237v. The SSR changes that and with a twist of the know it can go from 237v down to about 30v-40v. So when I hooked up to the output side I was calculating the watts. Like in the first pic where both elements are running at 233v x 21.4 amp for 4926 watts each. (Don't know how they advertise 5500 watts, I only have a couple more volts to put too them.) If I am hooked up to the input side of the SSR, I will read 237v wile the output to the element when turned down may be only 150v. If there were let's say 15 amps (just for reference) the output reading tells me there is 2250 watts of power at an element. Hooked up to the input side reading 237v x 15 amps tells me there is 3555 watts. Wouldn't the 2250 number be correct? Am I missing the boat here? Guys, by far I am not arguing by the way, just shooting for an education. I greatly appreciate everyone's input.

How do you calculate the watts from either side?

[likker liker]

Well did some stripping runs yesterday and a spirit run today. Near the end of the spirit run I noticed one of my meters was off. I opened the box to take a peek and saw the smoke had escaped from one of them and the other one was looking the same so it is not far behind.

It is the DROK® AC 80-300V/50A 110V 220V Digital LED Amp Volt Meter Ammeter Voltmeter Gauge+Current Sense transformer sold on Amazon. Don't really know what's wrong here. I ordered two more and will see if they hold up.

Wide Open.jpg

Where they burned:

Smoke Out 1.jpg

Smoke Out 2.jpg

When I get the new ones I will make sure the wire to that transistor is pushed away from the connector in case it gets that hot again.

Thanks for all the information and the update. Just a few days ago I got my controller working. The transistor in my controller was very close, I pushed away from the other stuff. And I'll make sure to have some air flow thru there.

[Edwin Croissant]

If I don't know the voltage and amperage output going to the element how do I determine the wattage?

You know the current so you can use that as an indicator. If you know the resistance of your element multiply that number with the current and again with the current (P=I2R) and if you meter is a true RMS meter (which I doubt) you have an indication of the power. Please note that your element's resistance will increase as it gets hot.

Edwin, I read your post on the DL69-2048 meter you suggest and while I know you tried to dummy it down, you didn't dummy quite enough for me [..] Does that other meter just hook up to the input side and sense the circuit being used?

This meter measures a couple of thousand times a second the actual voltage and current value. It multiplies the numbers which each other and add the results together. After a second the result is the real power. So it only measure the power when there is current flowing through your element. I am working on a simple explanation but that is quite a challenge When I studied this subject it was not one of the easiest one's

[Yummyrum]

I agree with edward ....LOL ...there is no easy way to explain it but here is a pic I drew for a similar question on another Forum .

The voltage and current is always changing through out the cycle so for the formular P=I x V to be correct , we measure the Voltage and Current in RMS Volts ( Root Mean square ) its a sort of average of the full cycle .The result is that the RMS voltage has the same heating ability as the equivalent DC voltage .....clear as mud .
You can see that there are areas with lots of energy and areas where there is little ......the RMS is the average

You will see from the top pic below that the RMS voltage is lower than the peak . In a true sinewave , the Peak voltage =RMS voltage x 1.414

The same applies to "chopped" up AC LIke the output from a phase controller ( EG a SSR with a Pot ). except that the RMS voltage will be lower than the Peak and there is no direct relationship .
The ONLY way to measure the RMS voltage of a NON SINEWAVE is to ....as Edward said....take many samples and carry out a mathmatic average of the samples to arrive at a TRUE RMS Voltage or current .

Many cheap Volt meters simply measure the peak voltage and scale it , while others do a crude integration , so while you do get a reading , its way off what the real value is when used on other than a pure sinewave .IE measuring the output from a controller

Edited in Red

[HDNB]

first lemme say that the meter prolly blew for the above reasons.

now if you you want to continue reading electricity for dummies (cause i r one) here is the best HDNB sparks for the layman.

electricity is like water.
A resevoir is like a battery, full of water instead of electricity.
Voltage is the measure of the potential work it can do. like water behind the dam, you can get more work out of 240 feet of water than you can 120 feet.
the flood gate on a dam is like a transistor (i.e. scr) it opens and closes to allow water (or the case of transistor, electricty) to flow.
the flood gate can open a little, or a lot. (amplitude) so can a transistor.
if it opens and closes, it will create a wave. (perhaps you only want 120volts of the 240 available)*edit...cornfusing.
the flood gate can open slowly or quickly, and then close again, equally as quick. (frequency)
Once the flood gate opens and water is released, it falls in a current. this is kinetic energy. energy in motion. just like electricity flowing through a wire, it is not going to do anything until it meets resistance, at which time the energy will change form.
When the water meets the resistance of a turbine, friction causes the turbine to spin. the energy of the water current is dissipated as heat (blade surface, bearings) and the rest is used to the electric generator to make electricity. (by moving the stator against the magnetic field, which takes a bit of force)
the electricity can be stored in a battery (resevoir) to be used later...say to power a pump that would force water back up the hill and fill the resevoir again so we could open the dam and force more water through the turbine and make more electricity to....wait a minute...

Eureka! i just invented a perpetual engine! power for everyone for free!!!! woo-hoo!

so in the case of the still heater, the resevoir of electricity in your service can be controlled by the flood gate that is your ssr, scr, and the power will flow until it meets the resistance of the element, at which time it will change form and become heat.


AND....that is why measuring the voltage after the water has gone through the flood gates is a moot point, and will burn out your meter. (you are basically using a depth meter to measure the frequency and amplitude of the water leaving the floodgate)

now the flaming can begin...but before it does...i didn't say you could design an electronic circuit with the info, this is just a no- math involved understanding of the broad strokes of whats going on under the hood.

hope it helps.

[Yummyrum]

HDNB .I like your water analogy but it needs a few clarifications as ofter too simple leads folk on the wrong way of thinking

the flood gate on a dam is like a transistor (i.e. scr) it opens and closes to allow water (or the case of transistor, electricty) to flow..

correct but transistors and SCR's ( Silicon Controlled Rectifiers ) and Triacs are very different types of devices
Transistors and SCR's only conduct current through them in one direction whereas Triacs ( the active devices in SSR,s ) conduct current in both directions and are suitable for Alternating current applications

SCR's and triacs are on or off devices or to use your Floodgate analogy , the gate is fully closed or fully open ....there is no half open with these devices

Transistors on the other hand can be and this makes them perfect for use as amplifiers in the Analog electronics . However , when a transistor is in a half conduting state ,it is dissipating energy as heat .
When its Driving say a set of speakers at around 100 watts , the heatsink on an Amplifier gets quite hot .
Now try and use a transistor to run a 5kW element and you will find that the heat sink will suddenly need to be about the size of a 50" TV and will fry an egg quite nicely .

This is why transistors are not used in "linear mode " to control high powers ...IE ....they are useless as being flood gates half open .

However Transistors can be used as switch devices . If they fully open and fully close really quickly the average current through them can be controlled . ...IE...open and close the flood gate very quickly and you control the average flow of water . When run like this all semiconductors dissipate very little power at all

That is why a heatsinks on semiconductor controllers like on a SSR or those things they call SCR controllers ( which are really Triac controllers ) have small heatsinks about 2" verses one about 50" square
They dissipate no power when off , Bugger all when on .....but when they switch that is when they get hot

if it opens and closes, it will create a wave. (perhaps you only want 120volts of the 240 available)
.

The wave thing is confusing . It gives to me the impression that a nice rolling wave is created when the current is opened and closed . This is far from the truth. All the switching controllers that use phase control give a waveform like the lower pic in the diagram I posted above ecept that I have flipped the dotted line negative half cycle up into the positive to show RMS

[HDNB]

yummy, i was on the fence on that line too. your right it's confusing. lets block that one from the analogy.

[skow69]

The internal power supply of these meters is based on a serial capacitor (the big red thing on the left) a diode bridge (the tiny black ic with 4 connections), a couple of resistors, a zenerdiode and a low voltage capacitor. This works as long as the supply voltage is a nice sine wave. Connect this supply to the output of a SCR and the sharp rise time that occurs when the triac is fired result in a high current spike through the capacitor. It looks that the resistor next to the connector is dissipating this power and overheats. After some time the capacitor will fail to.

Edwin, are you saying they put capacitors in series on the input to make a voltage divider so they don't have to use a transformer?



That would explain some things.

[Jacksonbrown]

I use the mechanical and fluid analogy's too.

Volt = pressure = potential = meters head

current = flow rate

Too many volts means too much current, in a small wire it makes the smoke come out.

Too higher pressure in a pipe is trying to squeeze too much flow through and the pipe may blow

How about a river bursting it's banks.

springs/caps?
grears/coils?

resistance to flow is...

[Edwin Croissant]

Edwin, are you saying they put capacitors in series on the input to make a voltage divider so they don't have to use a transformer? That would explain some things.

This is the schematic of the power supply of the DL69-2048:

At 50 Hz the 680 nF capacitor has an impendance of 1/(2*Pi*f*C)= 4681 ohm. Voltage drop rectifier bridge and zener's is ~6.5 V so current is (220 - 6.5)/4681 = ~45.6 mA. Apearant power is 0.0456 * 220 = 10VA (I measured 10 VA) . Dissipated power (heat!) is 0.04562* (22 + 51) + 0.0456*6.5 = 0,45 W (I measured 0,4 W). The 680 nF capacitor act like a battery, the charge it receives is returned to sender on the next zero crossing. The electricity company can charge for 0.45 W but has to swallow the transportation losses for 10 W

Worst case scenario is when the power supply is switched on on the moment the line voltage is at it's maximum, the 680 nF capacitor act like a short and the current is limited by the 51 and 22 ohm resistors. The top value of 220 V is ~ 310 V so the current spike is ~4 A!
When you connect the meter on the output of the SCR and you set the SCR at half power you have this worst case scenario 100 (or 120) times a second for as long as the meter lives

[skow69]

Thanks Edwin. I appreciate your time. I have a couple of follow up questions.

Hound Dog, if you want us to take this somewhere else, I'll be happy to, but it seems related to me.

1 Why a cap at all? Couldn't you replace the cap and the 51 with a power resistor, say 4.7k, 20 watt, wirewound? Prolly $10 ea?

2 Or I think you're saying you could fix it by using a cap rated for ~350 VAC. Might be the size of a lunchbox, I suppose.

3 Either way, trying to run it on reduced input voltage, at some point this regulator would starve the meter for current, I think. Which then makes an analog meter pretty attractive.

Or that magic meter you found would be just the ticket, wouldn't it? The one that somehow sniffs out the real power from the other side of the street cuz it samples really fast. [Har!]

Am I getting warm, here, or still missing something?

EDIT: My head hurts. I'm gonna go drink beer and watch pretty girls take their clothes off for a while.

[Hound Dog]

Hound Dog, if you want us to take this somewhere else, I'll be happy to

Keep it rolling here guys, I'm tying to learn something too!

[Edwin Croissant]

Thanks Edwin. I appreciate your time.

I'm enjoying this I realize now that when I studied this subject more then 40 years ago I was a monkey they taught a trick. Enough to pass my exams. Luckily I never had to use this in my work

2 Or I think you're saying you could fix it by using a cap rated for ~350 VAC. Might be the size of a lunchbox, I suppose.

Capacitor is already 630V rated.

3 Either way, trying to run it on reduced input voltage, at some point this regulator would starve the meter for current, I think. Which then makes an analog meter pretty attractive.

Yes.

1 Why a cap at all? Couldn't you replace the cap and the 51 with a power resistor, say 4.7k, 20 watt, wirewound? Prolly $10 ea?

I wouldn't replace the capacitor with a resistor, 20W is a lot of heat. Better to replace the existing power supply with a isolated 5V power supply. Those have the same size as the capacitor and can make the meter completely voltage independent. You need six terminals, two for the power supply, two for the Voltmeter and two for the Ammeter.
I don't understand why they are making this meters not like this. Now they can only measure line voltage and line current. For 50 cents more they would be much more versatile.

Or that magic meter you found would be just the ticket, wouldn't it? The one that somehow sniffs out the real power from the other side of the street cuz it samples really fast. [Har!]

Yes, this type of meters give you what you want to know, how much heat is going into your boiler. I received yesterday a Hiking dds238-2 sw. I ordered it 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).

Am I getting warm, here, or still missing something?

You are getting there

EDIT: My head hurts. I'm gonna go drink beer and watch pretty girls take their clothes off for a while.

I trust you enjoyed the show