What the heck is "duty cycle"
 

That's what I hear when I call up the stores and ask if they have a digital multimeter with 'duty cycle'? Is that the same as 'voltage event', 'auto ranging', 'data hold' or 'bar graphing'? No one seems to recognise the term 'duty cycle'. Can someone just reccommend a decent model?

Cap'n - do yourself a favor and look on ebay for a Fluke dmm with duty cycle. You can usually find one at a good price.

<< but I use analog meters only)>>

Another "Simpson 260" guy ???

In love w/my 260 ... [ all 5 of them]

I know what you mean..
I have them all, but have been using Simpson 260/s for 35 years and you just get to know how to read them without even looking at the scales, if you know what I mean..
Deflection Vibe, I call it....

Excuse me, but I don't have an answer yet
 

Anything at Radio Shack, Sears etc.?

This is decent for the $$$$

http://www.thetoolwarehouse.net/shop/FLU-78.html

I found two Flukes at WW Grainger. 6T087 for $70 and 6TO88 for $80. Both have duty cycle. They don't appear to have much else but I have a Beckman Industrial 360 to use for everything else. BTW, can duty cycle, in this case Lambda, be measured with a Snap On automotive occiliscope? I have access to one.

A scope is the "BEST"!
 

check out Stevebfl's article complete with pics: http://www.peachparts.com/Wikka/EngineControls

Here's a pic showing '50%' DC from Steve's article:.
http://pages.prodigy.net/jforgione/Stev_fig2.gif

You can use the old style analog meter to measure duty cycle. Duty cycle is defined at the ratio of "on" time to "off" time. On is defined as when the voltage is high and off time is defined as when the voltage is zero. If the on time is equal to the off time the duty cycle is 50%.

So given that as a basis for discussion one can read duty cycle using an old style meter. Here is how to do it.

It is important to know the voltage level during the "on" and "off" times. Knowing that allows one to make a simple reading and then calculate the duty cycle.

Lets assume that the voltage during the on time is 12v and zero during the off time. When we read a duty cycle voltage the meter will average or integrate the voltage between the on and off times. So if we were at 50% duty cycle then the meter would read 6v or half of the voltage during the on time. If we read 5v then we can calculate the duty cycle to be 41.55%. If we read 4v then we have a duty cycle of 33.33% and so on.

The formula is ---- duty cycle = Vread * 100 / Von

in our example 41.666 = (5 * 100) / 12

where;

Vread = voltage read my the meter
Von = voltage during the ON time

Hope I have not confused the issue. No need to go buy an expensive meter just to read duty cycle.

Dave I love to read your posts. I just wish I could understand them!:D
Jim, I read the article and that's why I need the "duty cycle". SB used a multimeter but if a scope will do it I won't have to buy anything.
I going to print Dave's reply and put it under my pillow tonight and see if I understand it tomorrrow! ;)

Since you have a scope you are all set. Just display the waveform and measure the ratio of on and off. And your done.

To expand on the previous good definition of duty cycle: The period of the event that duty-cycle represents does not have to be any set time-length. The first event to monitor is thus frequency. When asking about the meter, looking for duty-cycle, with salespeople that don't know what about the electronics being tested, frequency is something they usually understand. Frequency tells you how long the event takes. How much of that time is on or off is the duty-cycle. Equipment that measures frequency will usually do duty-cycle.

I bought a GREAT little DMM from the Sears Craftsmen tool catalog with Duty Cycle for $30. Actually they were having a 10% off sale so it was only $27.

It works great! All you have to do is look at the table showing various functionality for the meters they have. It can't be beat for the money.

Have a great day,

Thanks all.
Larry, do you know the model number of your meter?

I bought two from Sears 3 days ago. on sale for $17.99 each(close out?). By Craftman...Sears item#34 82040.

Looks like good fellow already posted for me.

It happened that I had a new Craftsmen tool catalog in yesterdays mail. I looked at the meters and they don't have the lower priced ones any more. Too bad, it's a great meter. I have several more expensive DMM's that I leave on the shelf most of the time now that I came up with that one. It's small and convenient with full functionality.

I would suggest you take Good Fellows part number and call the local Sears stores to see if they have any left in stock. It is an amazing instrument for the money.

When I was in college (Electrical Engineering) I was working in an electronic component burn in house at night. This was '73 '74 time frame. We had some 3 1/2 digit Fluke DVM's that cost well over $1,000 in seventies dollars. This little $27 meter will do anything they would do plus a lot more. That comment is without checking tolerances, but for most purposes the tolerance of most any DMM is just fine.

Good luck,

Sears doesn't have the 34-82040 but here are two that they do. Both claim to measure "frequency" and the red one measures temp to 1800 deg. It's $29.99. the the other says it has a scope. It's $53.99. What do ya think?

The $29.99 one

I want to see a picture of a Simpson 260, just to bring back memories;)

Here is one of my old favorites

http://members.aol.com/ajdalton7/260.jpg

Maybe we should start a Multimeter forum
 

While we're at it, what plugs into the DIN connector on the top one.

frequency function will do nothing for you. I will do my best to remember to get the number off of mine tonight and post it.

You need to look at the list of functions. It will be clearly labeled "Duty Cycle" or " % "

Happy hunting,

PS, I haven't seen a Simpson 260 in a very long time. It seemed like every one I ever had my hands on, had a broken case. My Dad had an optional case that had a rolltop door on the front. His was always in good shape. LB

Cap'n
 

the 'socket' provides means of testing transistors. Tests hfe (gain) of NPN or PNP transistors. Also that measures capacitance. Nice instrument to have for $53.99.

The pic of the first MM doesn't not have 'DC'. Can't make out the second one.

Art: cut my teeth on the 260s!

Re: Cap'n
 

Jim
Here is one your GrandFather propably did ....

ftp://members.aol.com/ajdalton7/analog.jpg

??????
 

Did I misinterpret this are or we talking about frequency in another context?

Arthur,

The Simpson looks just like the one I salvaged from work, back in the days I worked off-shore. The case was broken (like everyone Larry has seen) and the Techs were trashing it. I rescued it and used it for a long time, until my ex-brother-in-law borrowed it and lost it. All I have left is a set of spare leads for it :(.

Mike
Yeah- they were repairable
They even came with a schematic/trouble shoot section and a complete parts list.
I have one NOS still in the leather case that has never been used
for keeps-sake..

When I was a kid, we sent away and bought a Kit and assembled it .
Gone-bye days , for sure

Here is one I made years ago

http://members.aol.com/ajdalton7/heath.jpg

You guys are leaving me hanging here! I never got an answer to my last post about frequency.

As said , freq is the amount of complete cycles in a time frame
of 1 sec.
Freq is measuresd in Htz [ times per sec.]
An example of this would be household current being 60 Htz [cycles per second]
Or , in England , 50 htz , etc....

Duty cycle is not by time , but by comparison of time ON to time
OFF of a cycle , So, it is measure in ratio/percentage.
Example :
A pulse of on time of 1/4 sec and off time of 3/4 of a sec. would be a duty [work] cycle of 25% or a ratio of same....

Generally speaking....

With a frequency of 1hz.

OK here it is in living color. One picture is worth how many words?

Yep.....

Wow, doesn't anybody read . . .
 

What do you think is displayed in Steve's picture?

How do I get into these messes??
 

So, frequency and duty cycle..... are/are not the same? An instrument that measures frequency will/will not/might measure duty cycle??:confused:

Cap't - frequency and "duty cycle" are NOT the same. Think of turning a light switch on/off. Duty cycle is the percentage of time the light is on versus off and frequency would be the time from when you first turned it on, then turned if off and then on again. The second time you turned it on would be the end of the first "frequency" cycle. If you did the complete "cycle" in one second with 40% of the time the light is on and 60% of the time it is off that is 40% duty cycle. That's a good explanation for a mechanical engineer isn't it. Just go get a high quality Fluke with duty cycle capabilities and you will not go wrong.

At the risk of oversimplification....
 

Whatever meter I buy had better say "duty cycle" on the face somewhere?;)

Re: At the risk of oversimplification....
 

It may just say "Pulse" or "Pulse Width"
If so, it does measure Duty Cycle

Flukes don't get into Duty cycle until you get into their 80 Series meters....

*DUTY RATIO
The ratio of pulse width to repetition period. Also known as Duty Cycle.

Bingo!!
 

Now I can go to the store and shop with a clear idea of what I need!

A big ol THANKS to all!!

duty cycle
 

I was an electronic technician a long time ago, I don't know what your measuring, but here is a typical real-life duty-cycle reading: A cheap welder will say it has a 20% duty cycle. This means it will operate one fifth of the time without overheating, lets say 5 minutes on, and cool down for 25 minutes. A higher quality welder will have a 100% duty cycle, you could use it continuously without it getting too hot. Lorenzo in Great Falls.......

Sorry Lorenzo but . . .
 

the duty cycle you described is 16% not 20%.

The formula is ON/ (ON + OFF): so 5 / (5 + 25) = 0.16 = 16%

Sorry about that but couldn't let it go. This thread has been a nightmare! :( So might as well add to it!

Cap'n may end up buying a Lexus!! :D

I may get confused.... but....
 

If I were going to buy a Lexus, I'd just buy a Toyota and save the extra money. IMHO that apple didn't fall far from the tree!!;)

Thought provoking
 

With the number of reads and replies this post has had, apparently those salespeople I was dealing with were not the only people that didn't have a clear understanding of the term!;) Of course I knew all along.....:p :p :p :p :p