Quest M3 Mods - Page 25

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Beanz

#241: Post by Beanz »

Using a Kill A Watt solution is really easy for most roasters to read the power being used by the Quest. It is as simple as plug and play. I must point out I love Murata products so I like the application above.
Isolating the power consumed by the fans for our coffee roasting applications is not really going to provide additional useful information, for me it is interesting but not useful, it will not change my roast. Using a Kill A Watt style meter including the power consumed by the fans does keep all roasters on the same page with our measurement technique and readings.
Being able to see for example 900W consumption during the roast and then 775W at 1C and then being able to repeat that on the next roast is what I believe we are chasing.
If you guys tell me you apply 1000W at 1m 30 sec and then 800 W when you hit 1C then I can sit on the other side of the world and try to replicate what you have achieved.
The Quest's ability to let us share this Roast Power information makes it so good
Try replicating a power reading on a Kill A Watt just using the Quest analogue current meter to adjust the settings, it is very difficult to consistently hit the same power just reading the analogue meter.
My roasts tend to indicate that +/-50W at 1C can make or break a roast so I am sold on Digital Power meters

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FotonDrv

#242: Post by FotonDrv »

Beanz, good information! I was unaware that a Kill a Watt would handle the load.

Is that a 120V Kill a Watt?
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nate74

#243: Post by nate74 »

+1 for the Kill-A-Watt power monitor on the Quest. I used a Kill-A-Watt P4460 EZ model, like $25 on Amazon, on my quest for 3 years with no issues. I believe they are rated @ 125V 15A so the load should be no problem at full power. You can even program in your electrical cost per KW and it will calculate the cost of running the Quest. :)
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Beanz

#244: Post by Beanz »

nate74 wrote: it will calculate the cost of running the Quest. :)
That just might spoil the fun

Beanz

#245: Post by Beanz »

FotonDrv wrote:Beanz, good information! I was unaware that a Kill a Watt would handle the load.

Is that a 120V Kill a Watt?
You would need to check the load capacity for the ones in your market but Nate covered that

In Australia we are 240V
As Watts= Volts times Amps we can compare our roasting in the same unit of measure, Watts, in different locations with different line voltages. When you guys post your current settings from the analogue meter I have to do a quick conversion to understand the power you are using. Kill A Watt or similar devices overcome that and are more accurate but more importantly allow you to replicate a profile.

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AssafL

#246: Post by AssafL »

Kill-a-watt type device would work.

One thing I'd try to ascertain from the maker is whether it calculates RMS. Since the quest uses a lamp dimmer style control (chopping a portion AC signal using a Triac) - the crest factor changes between settings (full sine wave at 100% or chopped sine waves at less than 100%). If it doesn't do RMS then usually the results will vary greatly as it will be adjusted for a sine wave (1.41 root of 2) crest factor.

It is less important if everyone uses the same Kill-A-Watt and the same supply voltage (110 or 100 or 220 or 240V) since at that point the reading on one Kill-a-watt would be the same as another - but any relationship to actual heating power would not be true. You can't compare the readings from different types as they may have different ways of calculating the voltage of the chopped AC as well as between different supplies (as the chopped AC would - again - have a different crest factor).

Look for a True RMS Kill-a-watt. AFAIK - the P3 International model (the brand Kill A Watt) P3 does do RMS. I don't know about the ALI Express versions though.
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max

#247: Post by max »

AssafL wrote:One thing I'd try to ascertain from the maker is whether it calculates RMS. Since the quest uses a lamp dimmer style control (chopping a portion AC signal using a Triac) - the crest factor changes between settings (full sine wave at 100% or chopped sine waves at less than 100%). If it doesn't do RMS then usually the results will vary greatly as it will be adjusted for a sine wave (1.41 root of 2) crest factor.
Please correct me if I'm wrong; this is outside of my field of expertise.

Shouldn't a device which supplies the power factor also display the real power? Or are there "tricks" for faking the power factor? None of the meters I looked at before my purchase mentioned RMS, but power factor was listed. This would be easier to look for in consumer devices.

On the other hand, isn't this necessary if the device is marketed as measuring power consumption? Otherwise it would also not correctly measure non-resistive loads, nor portable radiators using (I'm guessing) a phase fired controller. This seems like a serious omission in a home environment.
It would thus have to calculate the time-averaged consumption, reducing to the RMS in the resistive case of the Quest.

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AssafL

#248: Post by AssafL »

RMS is about waveform shape - not active vs reactive power.

When you have an inductive or capacitive load there is a phase difference between the current and the voltage. The angle between them is phi and there is the active power (you called it "real"), inductive power (so it isn't "real") and apparent power (the total, expressed in VA).

An RMS value of a waveform is the equivalent D.C. Value that would heat exactly the same.

You could measure power using a regular non True RMS assuming the load is resistive. So a heater with thermostat is resistive and the measurement will be accurate.

But, in other cases the apparent power is always Vrms*Irms.

I believe most of these devices probably use an energy meter chipset which should always do RMS. But I am not certain of this.

(BTW - reactive power - if it isn't real why is it so important? well, the power isn't real. But the current component is very real. While it isn't working for you - it does flow and incur losses I^2*R on the power lines and transmission systems - hence utilities track cos(phi) closely; also, utilities have to size the cables for the excess current which is yet another expense).
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max

#249: Post by max »

I am not trying to dispute what you are saying, only clarify my thoughts:

What we desire is a device that calculates the active/real power.
  1. As you say, apparent power is the product of RMS voltage and current. However, unless there is a "trick"/"cheat" (is there??), to display the power factor (=active/apparent) it would have to calculate the active power, thus having the property you desired. My idea was therefore that it could help non-technical Quest users to look for one which displays the power factor, even if RMS is not mentioned.
  2. The other half was a thesis why devices that don't calculate the active power (correctly) should be uncommon. In order for a device to calculate the active power of a non-resistive load it would need to calculate the (averaged) integral of the (scalar) product of voltage and current, so even with sinusoidal waves time-averaging would be necessary.
    Calculating RMS would just be the resistive special case of such a calculation (regardless of waveform shape).
    However, I have no good feeling for the relative importance of non-resitive measurements in an home environment, so maybe the thesis fails.
Hopefully my meter (with PF) shows what I think it does :)

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AssafL

#250: Post by AssafL »

Dispute. I love dispute.

Now I get your point. Being able to calculate VA and W and Power Factor (and perhaps cos (phi)) - means that they probably average the calculations using RMS.

That is a very reasonable assumption. Much simpler than expanding it into a series...

I have to mull over the question if there is a shortcut. Thanks for disputing.
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