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Want to test line frequency before using HMIs


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#1 Jim Feldspar

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Posted 17 January 2007 - 11:36 PM

I'm hoping to use some small HMIs with some borrowed generators. I stopped and watched a film
shooting on the street once and talked to the generator operator. They were powering HMIs and he
told me that the generator was crystal sync controlled because it was important to mantain a
consistent frequency. The generator had a digital red readout which stayed at 59.97 HZ.

I'm not sure if this means that what we call 60 HZ is actually 59.97 or if this were an acceptable
deviation from 60 HZ but my question is how can I test the frequency of A. a generator and B.
a line coming out of an old, old house which might be questionable?

I've seen a clip-on amp probe used on a line to measure amperage draw but searching online
for information about tseting frequency all I
could find were products from which I'm guessing that an oscilloscope is needed.

Does anybody know? I'd really like to know, both for this practical apllication and now because I'm
really curious. Thanks.
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#2 Frank Barrera

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Posted 18 January 2007 - 12:11 AM

For proper HMI operation hertz frequency may fluctuate from -.03 to +.03. So a reading of 59.97hz is normal.

I have this type of meter in my kit. It requires that you place the two test leads (one black and one red) into the hot (red) and neutral (black) holes of any socket that is energized from the power source in question. This is a simple and safe procedure but you should at least discuss the meter and it's various functions with a qualified technician. The meter has a record function so that it will retain any reading above or below a specified measurement. It will also give off a small beep alarm if these numbers are attained.
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#3 JD Hartman

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Posted 18 January 2007 - 10:24 AM

Many DVMs (Digital Volt Meters) with have the ability to measure frequency. You might be able to find that feature in a clamp-on style meter, so that you don't lose the ability to measure current draw easily. I would school myself on generator operation, power distribution, engine and generator troubleshooting, voltage regulation and generator frequency control. Too many people throw around the term "Crystal Sync" with out understanding what it means or how it is acomplished. When do you need a genny with tight frequency control? What types (and brands) of generators are acceptable for what types of lighting instruments? Knowing the answer the previous two questions will make you more of an asset.
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#4 Matt Workman

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Posted 18 January 2007 - 10:40 AM

Using HMIs with Electonic Ballasts you can use regular "non-sync" generators. The newer Arri ballasts have a flicker free mode which can cause an audible "humm." Even my old Lee HMI's work fine on Home Depot 5600w Honda's.

Magnetic ballasts I hear that you need a clean source. I've never used them though.

Cheers,

Matt

PS: I would really love to learn about generators/electricity in more depth. Bestboy time. :lol: JD where would you recommend researching. I've read the Set Lighting Technician manual several times.

Edited by Matt Workman, 18 January 2007 - 10:41 AM.

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#5 Jim Feldspar

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Posted 18 January 2007 - 10:44 AM

For proper HMI operation hertz frequency may fluctuate from -.03 to +.03. So a reading of 59.97hz is normal.

I have this type of meter in my kit. It requires that you place the two test leads (one black and one red) into the hot (red) and neutral (black) holes of any socket that is energized from the power source in question. This is a simple and safe procedure but you should at least discuss the meter and it's various functions with a qualified technician. The meter has a record function so that it will retain any reading above or below a specified measurement. It will also give off a small beep alarm if these numbers are attained.


That's great. I had gone from my immediate need to simple maddening curiosity.

I have talked to electricians before as I learned how to use a volt meter to plug into wall outlets
(and have somebody switch on a light or flip a breaker) to determine circuits but I will get some
advice bfore proceeding with this. However, unless I can find a less expensive meter. I may see
if I can narrow down the generators to the one that I'm likely to use and bring it to a friendly
electrician and see if he can test it while eating the pizza that I bring. I'd like to let it run and test
it over half an hour or so to see if stays consistent, also maybe having a load on it to test under
those conditions. Thanks!
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#6 Frank Barrera

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Posted 18 January 2007 - 10:54 AM

I would also note that when buying a multi-meter that can measure Hz it is important to make certain that the meter is capable of reading "True RMS". RMS stands for root mean square. Now this starts to get a bit too mathematical for little 'ol me but apparently True RMS meters garuntee accurate readings. When reading voltage and amperage it is not critical to have the most sophisticated equipment. But if you really need to know what is going with the Hz then you really need to know what's going on with the Hz.

So, I learned a long time ago to just stick with anything made by Fluke.
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#7 Jim Feldspar

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Posted 18 January 2007 - 11:02 AM

[quote name='JD Hartman' post='149215' date='Jan 18 2007, 07:24 AM']Many DVMs (Digital Volt Meters) with have the ability to measure frequency. You might be able to find that feature in a clamp-on style meter, so that you don't lose the ability to measure current draw easily. I would school myself on generator operation, power distribution, engine and generator troubleshooting, voltage regulation and generator frequency control. Too many people throw around the term "Crystal Sync" with out understanding what it means or how it is acomplished. When do you need a genny with tight frequency control? What types (and brands) of generators are acceptable for what types of lighting instruments? Knowing the answer the previous two questions will make you more of an asset.[/quote]


"Too many people throw around the term "Crystal Sync" with out understanding what it means or
how it is acomplished."

It's so insightful that you say this because as I was making the post it occured to me that crystal
sync is also used in camera motors and I'm able to answer very authoritatevely "Oh, That Bolex
is great but if you want to shoot sync..." etc. and it occured to me yeah, how does
crystal sync work? I don't know. So, that's part of of my new research list, along with all of your
great suggestions about reading up and talking to people on all those other related subjects.

I'll be doing some reading and buying some pizza for my local knowedgeable friends. (I like to
do as much reading as possible first. It's like posting here. People are usually glad to answer
questions but if you use up your questions with things that you could have looked up, then you
may lose your chance to ask the questions that couldn't be looked up because you've used up
the fifteen minutes the person made room for in his schedule or the patience of the forum
members.)

By the way, what's a good light to use for making a film? (KIDDING!!!)


[quote name='Matt Workman' date='Jan 18 2007, 07:40 AM' post='149219']
Using HMIs with Electonic Ballasts you can use regular "non-sync" generators. The newer Arri ballasts have a flicker free mode which can cause an audible "humm." Even my old Lee HMI's work fine on Home Depot 5600w Honda's.

Magnetic ballasts I hear that you need a clean source. I've never used them though.

Cheers,

Matt

Thanks, Matt. I'm planning on using Hondas. Mostly shooting outdoors at night so if there is a
"humm" I ought to be able to get the ballast(s) far enough away from any dialogue.

Never seen a Lee light. Do they still make them? Can you get lamps okay?

From what I hear magnetic ballasts weigh a ton so people (the crew anyway) probably aren't
as eager to lug them around but maybe they're a cheaper rental.
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#8 Frank Barrera

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Posted 18 January 2007 - 11:05 AM

I'd like to let it run and test it over half an hour or so to see if stays consistent, also maybe having a load on it to test under those conditions.


Allthough your friend may enjoy the pizza, this would be a total waste of time. The vagaries of a generator are too great. In the field any number of things may occur which would impact the units ability to output a steady Hz cycle. That's why the fellow you saw on the street one day was monitoring the Hz as you were talking with him. That is why there is a record function on meters. In short, checking the Hz today will tell you nothing about the Hz tomorrow or next year.
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#9 Jim Feldspar

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Posted 18 January 2007 - 11:14 AM

I would also note that when buying a multi-meter that can measure Hz it is important to make certain that the meter is capable of reading "True RMS". RMS stands for root mean square. Now this starts to get a bit too mathematical for little 'ol me but apparently True RMS meters garuntee accurate readings. When reading voltage and amperage it is not critical to have the most sophisticated equipment. But if you really need to know what is going with the Hz then you really need to know what's going on with the Hz.

So, I learned a long time ago to just stick with anything made by Fluke.



Good point! For my other needs a less expensive meter might be okay (the difference
between
a reading of 115 volts on one and an accurate 112 on a more accurate more expensive meter
is a bigger percentage but probably not as critical as being off within the narrower marigins
of " -.03 to +.03." frequency deviation for proper HMI operation and if a less expensive, less
reliable meter tells you that you're off -0.5, well what do you do? You can't neccesarily see
the flicker with your eye.

Do you keep shooting the rest of the night or shut down or waste hours
getting a new meter or generator, even though you know that -0.5 on your meter might
really be a slighty off reading of an acceptable -0.3? You're right, saving that two hundred
bucks is going to feel really worth it when an entire production has stopped in its tracks and
you can't even be sure if your information is accurate!

Awesome, thanks!
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#10 Jim Feldspar

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Posted 18 January 2007 - 11:24 AM

Allthough your friend may enjoy the pizza, this would be a total waste of time. The vagaries of a generator are too great. In the field any number of things may occur which would impact the units ability to output a steady Hz cycle. That's why the fellow you saw on the street one day was monitoring the Hz as you were talking with him. That is why there is a record function on meters. In short, checking the Hz today will tell you nothing about the Hz tomorrow or next year.



Indeed. That guy's job was to stand guard at the generator and monitor it (and that was
an expensive blimped generator from a film rental house and probably as
reliable as any one out there.)

However, if I can find a generator that looks reliable, I may go with it and see if I can
minimize my use of HMIs and see how that goes, while increasing what I can do by other
means. This should be less risky than relying on the HMIs for the entire shoot, For example
if I use 1200w PARS to light large night ext. distant backrounds in master shots and use
tungsten on the foreground talent, that might work okay and even be able to be used if there
is some flicker on that abandonded warehouse in the background.

Thanks for all your responses! Am I going to get a bill?
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#11 Matt Workman

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Posted 18 January 2007 - 11:44 AM

This is an interesting thread to me, I'm learning too.

Lee is a UK company. I think they still make lights? But the rest of my lights are Arri, Kino, etc. The Lee's use standard double ended HMI globes. Osram or G/E.

Your best bet when using generators is to have an operator. That is usually required by any rental company, escpecially with generators large enough to be towed.

I know a rental house who has several professional movie generators and one of them caught on fire on a large shoot. No one was hurt BUT even a "Professional" generator under the close eye of an operator can be very dangerous. They need constant maintenance, like a car.

Anything larger than a 5600w Honda you shouldn't even be touching unless you have been trained.

Cheers,

Matt

PS: We can split the costs of this thread :ph34r:
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#12 Jim Feldspar

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Posted 18 January 2007 - 11:52 AM

This is an interesting thread to me, I'm learning too.

Lee is a UK company. I think they still make lights? But the rest of my lights are Arri, Kino, etc. The Lee's use standard double ended HMI globes. Osram or G/E.

Your best bet when using generators is to have an operator. That is usually required by any rental company, escpecially with generators large enough to be towed.

I know a rental house who has several professional movie generators and one of them caught on fire on a large shoot. No one was hurt BUT even a "Professional" generator under the close eye of an operator can be very dangerous. They need constant maintenance, like a car.

Anything larger than a 5600w Honda you shouldn't even be touching unless you have been trained.

Cheers,

Matt

PS: We can split the costs of this thread :ph34r:


I'm definitely not going bigger than the 5600w.

Thanks for offering to $ chip in but now Frank is really going to charge us!
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#13 JD Hartman

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Posted 18 January 2007 - 02:52 PM

Allthough your friend may enjoy the pizza, this would be a total waste of time. The vagaries of a generator are too great. In the field any number of things may occur which would impact the units ability to output a steady Hz cycle. That's why the fellow you saw on the street one day was monitoring the Hz as you were talking with him. That is why there is a record function on meters. In short, checking the Hz today will tell you nothing about the Hz tomorrow or next year.


That is an interesting comment, Frank would you be kind of to expound on your post? What factors would affect the frequency output of a "crystal sync" generator over time?

As far as another person's comment on "trained" generator operators. Correct me if I'm completly wrong, but I thought the gen. op. card was basically a union Teamster thing. Kind of the same way they control transportation. It doesn't necessarily mean they are a diesel mechanic, licensed electrician or have received any special training. Rental houses send a driver/operator with the unit for many reasons, a few: big truck, very top heavy load; generator is worth more than $100k; no need to explain operating procedures to customer.

Edited by JD Hartman, 18 January 2007 - 02:53 PM.

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#14 Luke Prendergast

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Posted 18 January 2007 - 06:42 PM

I would also note that when buying a multi-meter that can measure Hz it is important to make certain that the meter is capable of reading "True RMS". RMS stands for root mean square. Now this starts to get a bit too mathematical for little 'ol me but apparently True RMS meters garuntee accurate readings. When reading voltage and amperage it is not critical to have the most sophisticated equipment. But if you really need to know what is going with the Hz then you really need to know what's going on with the Hz.



An RMS value is the mathematical DC power equivalent of an AC source. It has nothing to do with frequency reading.

IMPORTANT! Any meter plugged into mains MUST be CATII or CATIII rated! There may be a 600VAC range on the meter, but if it's not rated for mains use you're tossing a coin for your life. I've seen cheap, unrated meters and leads explode and melt.
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#15 Frank Barrera

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Posted 18 January 2007 - 08:27 PM

An RMS value is the mathematical DC power equivalent of an AC source. It has nothing to do with frequency reading.

IMPORTANT! Any meter plugged into mains MUST be CATII or CATIII rated! There may be a 600VAC range on the meter, but if it's not rated for mains use you're tossing a coin for your life. I've seen cheap, unrated meters and leads explode and melt.

Thank you Luke for pointing out my mistake. It's been a while since I was a best boy and I had that "True RMS" mantra in my head in respect to purchasing a meter. Of course it ONLY refers to voltage. CATIII rated meters are good for 600V which is well within the range of safety for our purposes.

What factors would affect the frequency output of a "crystal sync" generator over time?

JD-
I was under the impression that Jim was looking to use a "non-crystal sync" gennie to save money. These units are prone to Hz cycle fluctuations beyond that which would allow proper HMI operation. My point was that checking the Hz today thinking that this would be helpful for tomorrow is like saying checking today would be useful for usage next year. I was making no comment on the life of the unit itself.

Although, as far as I know there are no "crystal sync" gennies per say. There is no crystal sync technology involved. This is a convention of terms but nonetheless inaccurate. They are all controlled electronically and they rarely fail. But I do remember the odd event where high oil pressure or even water in a fuel line caused a malfunction with the controller.

Edited by Frank Barrera, 18 January 2007 - 08:29 PM.

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#16 Michael Collier

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Posted 18 January 2007 - 10:29 PM

Luke is right, RMS only applys to AC voltage readings. As for frequency in an old house, you shouldn't worry too much. Power generation facilities are mandated to be very regulated in terms of frequency. All of their calculations on effeciency are built on 60hz. Also if they were not absolutley locked, there would be serious feedback between generators if two power stations are used to feed one grid (and all power stations can feed other grids) also something to note, most wall clocks don't generate their own clock cycle to measure time, they count cycles from the wall outlet, so if your wall clock is time stable, so is your wall power frequency. Any power source (even in an old house) should be stable enough to run an HMI no problem. (this applies only to US power. I am sure most developed countries have similar strict controls, but I cannot speak first hand, and would suspect power generation in 3d world countries)
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#17 Jim Feldspar

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Posted 18 January 2007 - 10:39 PM

Thank you Luke for pointing out my mistake. It's been a while since I was a best boy and I had that "True RMS" mantra in my head in respect to purchasing a meter. Of course it ONLY refers to voltage. CATIII rated meters are good for 600V which is well within the range of safety for our purposes.
JD-
I was under the impression that Jim was looking to use a "non-crystal sync" gennie to save money. These units are prone to Hz cycle fluctuations beyond that which would allow proper HMI operation. My point was that checking the Hz today thinking that this would be helpful for tomorrow is like saying checking today would be useful for usage next year. I was making no comment on the life of the unit itself.

Although, as far as I know there are no "crystal sync" gennies per say. There is no crystal sync technology involved. This is a convention of terms but nonetheless inaccurate. They are all controlled electronically and they rarely fail. But I do remember the odd event where high oil pressure or even water in a fuel line caused a malfunction with the controller.

Thanks Luke and Frank. Yes, I am interested in seeing how a non-crystal sync (or if there
is technically no such thing, then a non film-industry generator, one not designated for
frequency consistent enough to stay within fluctuations that won't cause flicker) would
perform. Some people have reported that they've used Honda generators successfully
with HMIs, although not the type designed for controlled frequency with limited deviation.
I wonder if they have been able to do that because they'll perform that way reliably or
if they're reliable most of the time and so far these folks have made out okay.


Before I do any testing or use any test equipment, I plan on running everything by a local
licensed electrician.
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#18 JD Hartman

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Posted 19 January 2007 - 12:07 AM

Frequency stabilization is maintained by keeping the engine rpm's consistant, regardless of load. On older generators and some of small cheap portables, it's done by a combination of an engine driven governor and a throttle accuator arm. This doesn't mean that there will be a large frequency drift as the load changes, but it does mean that, being mechanical, it can't react quickly. Electronic frequency stabilization, referred to as "crystal sync", uses a feedback circuit loop (sometimes with a quartz crystal as a reference) to monitor and adjust output frequency. But the 60Hz is still maintained the same way, by controlling engine speed, just more accurately and more quickly. Many small generators, like the Hondas have electronic frequency stabilizaion. Check the manufacturers information to be certain. Small generators often have other problems, like poor voltage regulation, gravity fuel systems (no fuel pump, too expensive) and output ratings that reflect peak output instead of continuous duty.
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#19 Frank Barrera

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Posted 19 January 2007 - 05:47 AM

JD
What has been your experience with running HMIs off of "non crystal sync" putt-putts? Does anyone even attempt to do this? Or is some type of freq stabilisation required at all times.
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