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Don Corbeil
04-18-2016, 7:06 PM
Until recently, I thought that the only laser power meter available for testing my 80W CO2 was the synrad power wizard 250. They're pretty expensive, so I was looking around for alternatives. After some thread searches, I see that there are a few choices in both digital and analog metering. A few that I have seen are made by Macken (digital DM5 and P-series analog) and by Mahoney (analog).

For those who have used either (or both) I was wondering if you had some feedback on the accuracy and useability of these meters.
What reasons would you prefer a digital over an analog?
How does the synrad PW 250 compare to the macken digitals?
At Macken, they say both their analog and digital models are accurate within +/- 5%. I'm not sure about the Synrad. Have you found this to be true?
If I understand correctly, the analog requires a longer pulse to get accurate readings, and doesn't lock in on the highest read. One has to watch it and take note of highest reading.

Having used neither type, and wanting to purchase one in the near future, does anybody have a preference, and why?

Thanks!

Dan Hintz
04-19-2016, 6:47 AM
I prefer digital over analog mainly because I'm a hardware geek (not to mention reading the display is easier, and it can hold the reading). But the analog units are typically good to << a couple of % if you follow the proper procedure, so accuracy is plenty good.


I picked up a lightly used Power Wizard years back for 50% off, and I'd say it was a good purchase.

Keith Winter
04-19-2016, 10:44 AM
I find the PW 250 to be inaccurate at times, unless it's precisely held perfectly to the beam path. It does the job ok, and is probably the best measuring tool for the job, but I wouldn't want anything less accurate. In real life scenarios with a tube, mirrors, casing and everything else in your way, it's hard enough to hold it in the perfect alignment, I can only imagine how hard anything more picky or bulky than the PW 250 would be to use.


Until recently, I thought that the only laser power meter available for testing my 80W CO2 was the synrad power wizard 250. They're pretty expensive, so I was looking around for alternatives. After some thread searches, I see that there are a few choices in both digital and analog metering. A few that I have seen are made by Macken (digital DM5 and P-series analog) and by Mahoney (analog).

For those who have used either (or both) I was wondering if you had some feedback on the accuracy and useability of these meters.
What reasons would you prefer a digital over an analog?
How does the synrad PW 250 compare to the macken digitals?
At Macken, they say both their analog and digital models are accurate within +/- 5%. I'm not sure about the Synrad. Have you found this to be true?
If I understand correctly, the analog requires a longer pulse to get accurate readings, and doesn't lock in on the highest read. One has to watch it and take note of highest reading.

Having used neither type, and wanting to purchase one in the near future, does anybody have a preference, and why?

Thanks!

Don Corbeil
04-19-2016, 11:34 AM
Thanks for the feedback. I did a little further reading after posting, and what I found sort of addresses Keith's point about ease of use, which is a consideration. According to the specs I've read, all of the meters (both analog and digital) have an accuracy factor of +/- 5%. So that's good. It appears the main difference between the analog and digital meters comes down to the amount of time required to obtain an accurate read (60 seconds analog vs 4-5 seconds digital), and the ability of the digital to lock onto the max reading for a period of time. I could definitely see the benefit of a compact digital meter only having to be in the beam path a few seconds vs having to hold an analog steady for a minute in an awkward position. You'd also have to watch the analog display to note the max reading before it started declining. Not a deal breaker, but it is something to consider, especially taking into account how easy or hard it is to get into the beam path on one's own machine.

Mark Sipes
04-19-2016, 7:36 PM
Rent vs own. How often do you plan on testing your output? Or Maybe Own and then rent it out......new cash flow..



.

Gary Hair
04-19-2016, 8:10 PM
Rent vs own. How often do you plan on testing your output? Or Maybe Own and then rent it out......new cash flow...

Yep - Jorlink rents them for $85.00 vs $995 to buy.

Mike DeRegnaucourt
04-20-2016, 8:00 AM
I just saw this Instructable on a lower-cost method of measuring laser output. I have no idea if this works or not since I am by no means a technical expert when it comes to optics and laser output, etc... Maybe some of the experts could chime in out there as to the viability of this method of testing. I do know that it appears to be a potentially dangerous undertaking.

http://www.instructables.com/id/How-to-measure-CO2-laser-power-on-a-Laser-Engravin/

Bill George
04-20-2016, 10:19 AM
Don't waste your money on that one, to hard to hold in the exact place for the exact number of seconds. I sent mine back and eventually got a refund.

Don Corbeil
04-20-2016, 10:49 AM
Don't waste your money on that one, to hard to hold in the exact place for the exact number of seconds. I sent mine back and eventually got a refund.

Bill, did you end up replacing the analog mahoney with something else?

Matt McCoy
04-20-2016, 11:02 AM
Don't waste your money on that one, to hard to hold in the exact place for the exact number of seconds. I sent mine back and eventually got a refund.

I haven't looked too closely, but couldn't it be mounted in a jig are placed upright in the path?

Wolter Vanderwier
04-20-2016, 2:27 PM
You could put it in a cheap magnetic base from harbor freight http://www.harborfreight.com/multipositional-magnetic-base-with-fine-adjustment-5645.html

Bill George
04-20-2016, 8:43 PM
You could put it in a cheap magnetic base from harbor freight http://www.harborfreight.com/multipositional-magnetic-base-with-fine-adjustment-5645.html

Not a lot of room to mount and since the Test button was just a one shot deal, you really need to run a Test file at 100% power and low speed for 20-30 seconds. Since I run a home machine shop I have several mag base holders available.
Never puchased another, but when I ran the new tube to cut 1/4 inch acrylic I could tell, and used that kind of a benchmark.

Greg Holt
04-22-2016, 6:46 AM
I have one of those Mahoneys.

Is it accurate? I would not know. Nothing to compare it to. But I believe it is close enough for my needs.

What I do know is that it is consistent. That means I can measure the laser power coming directly from the tube and then measure after any number of mirrors to see if I am losing anything.

I can also compare a reading a year later and see if the tube is losing anything with age/hours.

Measure a new replacement tube compared to that being replaced. Also compare one 80w tube in one machine to another 80w in the other machine.

I don't have any difficulty holding it in place for the required 30 seconds.

All up I am not sorry I bought it at all.

Don Corbeil
04-22-2016, 9:55 AM
Helpful feedback, Greg. Thanks.

Gene Uselman
04-22-2016, 2:50 PM
I have one of those Mahoneys.

Is it accurate? I would not know. Nothing to compare it to. But I believe it is close enough for my needs.

What I do know is that it is consistent. That means I can measure the laser power coming directly from the tube and then measure after any number of mirrors to see if I am losing anything.

I can also compare a reading a year later and see if the tube is losing anything with age/hours.

Measure a new replacement tube compared to that being replaced. Also compare one 80w tube in one machine to another 80w in the other machine.

I don't have any difficulty holding it in place for the required 30 seconds.

All up I am not sorry I bought it at all.

Same here- all you need to do is keep the beam on the black alum target- does not have to be in one spot- it just absorbs the beam and heats up. I wrote a program with a spiral (5mm overall) and slowed the laser down till I had the required number of seconds. You can also develop a 10 sec program at a level that your laser will not actually fire (<9% on mine) to give you a chance to get the the back of a larger laser and get 'set'. It is calibrated when it is built and is way accurate enough- mostly you are using it for a reference.

Don Corbeil
05-01-2016, 12:21 PM
I was about ready to go with an analog, but then found a nice used Macken DM5 (with new probe!) on ebay for $150.
With the detachable probe on a flexible cord, it should be easy enough to place it, even in hard to get to spots.
336712

Keith Winter
05-01-2016, 5:19 PM
I was about ready to go with an analog, but then found a nice used Macken DM5 (with new probe!) on ebay for $150.
With the detachable probe on a flexible cord, it should be easy enough to place it, even in hard to get to spots.
336712

Sounds like a steal don! Nice find! :)

Dave Sheldrake
05-01-2016, 6:05 PM
What I do know is that it is consistent

Sadly consistently bad in most cases as are most thermal calorimeters when it comes to laser beam measurement. About all they are good for is an idea of change rather than accurate readings as a number of factors that affect laser power are ignored in such a test.Up against my lab rig they can be anything up to 30+% out :(

Don Corbeil
05-02-2016, 11:28 AM
Sadly consistently bad in most cases as are most thermal calorimeters when it comes to laser beam measurement. About all they are good for is an idea of change rather than accurate readings as a number of factors that affect laser power are ignored in such a test.Up against my lab rig they can be anything up to 30+% out :(

Sadly, most of us also don't have access to a lab, Dave!
So we have to make do :)

Dave Sheldrake
05-02-2016, 3:23 PM
Sadly, most of us also don't have access to a lab, Dave!
So we have to make do :)

was more intended to show how inaccurate they can be :) ( I mean the cooking thermometer versions with a block of ally on the end)

A good way to make your own is google Dr Lindsay Wilson as he has a full run down on making one for about 5 bucks (and is an all round clever chap)

Don Corbeil
05-02-2016, 5:50 PM
was more intended to show how inaccurate they can be :) ( I mean the cooking thermometer versions with a block of ally on the end)

A good way to make your own is google Dr Lindsay Wilson as he has a full run down on making one for about 5 bucks (and is an all round clever chap)

Dave,

Aren't the digital type (ie synrad PW250, macken DM5) also thermal calorimeter types, ie measuring changes in temperature?

Dave Sheldrake
05-02-2016, 5:59 PM
Dave,

Aren't the digital type (ie synrad PW250, macken DM5) also thermal calorimeter types, ie measuring changes in temperature?

yup many are Don but they are made to NPL Traceable standards rather than a well intentioned bodger with some super glue and a $3 ebay cooking thermo :) the macken and power wizzard are excellent and will 99% of the time hit within 10th's of a watt at worst and often better than that even. For all practical intent and purpose the Mac and the PW are lab standard :)

What causes me the most concerns are the home made and cheaply made chunks of aluminium glued onto stainless cooking thermo's that are then used to phone the suppliers with complaints of "My $10,000 80 watt machine is only putting out 70 watts according to my $5 meter" :)

Don Corbeil
05-02-2016, 6:42 PM
Thanks for clarifying. I'm relieved :)

Scott Cowell
05-03-2016, 7:36 AM
Don,

I am nearing the purchase of my first laser and have been doing quite a bit of "research" which, of course, includes watching "Tool-Porn" on YouTube. If you lookup:RDWorks Learning Lab 53 Power Meters and the doHICky comparator


you will find a retired gentleman in the UK who shares his adventures in learning about his Cinese E-bay laser engraver. His Youtube account is SarBarMultimedia. In this particular episode he explains power meters, checking his machine, and how he built his own meter. I believe he was even selling the tough to build bits directly. I find him interesting, entertaining, educational and inspirational. If and when I decide to purchase a power meter I will certainly look him up. I would rather send my hard earned cash to a fellow hobbyist rather than a mega-corp. - I have no problems with mega-corps, but you just gotta support the little guy who lets you look over his shoulder, ask silly questions and who shares his successes as well as his follies. After all, isn't that why we do forums? To help each other? - Enough soap box; more cheerleading: Check out his channel, have fun, and let us know what you end up with and how happy you are with your decision.

Scott.

Don Corbeil
05-03-2016, 9:53 AM
Scott, welcome to the forum!
I haven't yet looked up your given source, but for me, I want the tool the works best for the job whether it be a corporation or a hobbyist that produces it. That said, I had already made a choice (see above) going with a used macken DM5. I will however look for the video you are mentioning. Good luck in your laser search.

Bill George
05-03-2016, 12:53 PM
I looked at the one on eBay also, and its rather vague in the description about the power level its intended for and the Product description on the their website lacks any user documentation? I would be gun shy on this item.

Don Corbeil
05-03-2016, 4:25 PM
Bill, I'm not certain which one you are referring to, but the one I ordered is coming over from Cork, Ireland. It was only after quite a few emails between me, the seller, and a Macken technician that I was sure I knew what I was getting. I am always very careful on ebay :cool:

Bill George
05-03-2016, 4:35 PM
I emailed the seller and got a very confusing answer about what attachment comes with the meter. They claim 5% accuracy the list of attachments for sale with the meter had no power or other details... just a bunch of part numbers and they don't cross over to anything on the website.

Ian Johnson
05-03-2016, 6:05 PM
I picked up one of the Ebay ones anyway. Looking at the description of the sensors on the Macken site, it appears to be the smallest one, meant for 20-220W which covers my 60w C02.

Greg Holt
05-03-2016, 7:14 PM
Sadly consistently bad in most cases as are most thermal calorimeters when it comes to laser beam measurement.
About all they are good for is an idea of change rather than accurate readings.........................

That was my point. Consistency is all I hoped for from it.

As I said I am not sorry I bought it. :)

Bill George
05-03-2016, 7:28 PM
Does it give readings consistent with what you expected?

Don Corbeil
05-03-2016, 9:08 PM
I emailed the seller and got a very confusing answer about what attachment comes with the meter. They claim 5% accuracy the list of attachments for sale with the meter had no power or other details... just a bunch of part numbers and they don't cross over to anything on the website.

Yes, it took a while of emailing back & forth to get the information I needed, including photos & part numbers. I eventually had a full list of the probes w/part numbers and photos and I ran these by the Macken tech, who identified them. That gave me some confidence in going ahead, as well as the 14 day refund window. Given the time difference, that also made the process slow. I should be getting mine by early next week, so I'll update here when I do.

Don Corbeil
05-06-2016, 8:46 PM
Received the macken today, and everything looks good. New probe, and the meter appears to be working properly.
I have a rather simple question for those with a trotec: How do you set up your trotec to get a meter reading? Is there a key function that will send a beam at 100% power for as long as you need to maintain it? I tried setting up a 1" spiral pattern (in cut mode, lens removed) centered on the probe that lasted 20 seconds (the time required on the macken), but I'm not sure that's the best way to take a reading on the speedy 300. For testing at the laser head, what distance do you have your probe from the head? Any suggestions?

Dave Sheldrake
05-06-2016, 9:31 PM
Keep the beam still Don and the meter fixed if possible or you will get some funky results :)

Lee DeRaud
05-06-2016, 10:54 PM
...rather than a well intentioned bodger with some super glue and a $3 ebay cooking thermo :)Ok, now I feel a lot better about springing for the fancy $16 thermometer from Williams-Sonoma. :cool:
I've got a 3oz lead wheel weight, what flavor epoxy do you recommend to attach it? :D

Dave Sheldrake
05-06-2016, 11:10 PM
The three most important words in the English language: "Front Towards Enemy".

What really worries me is I know what that means :)

Lee DeRaud
05-07-2016, 12:56 AM
What really worries me is I know what that means :)What really worries me is that they thought they needed that instruction.

TAMI WILSON
05-07-2016, 8:41 AM
I just got my Mahoney power meter. As many of you know Trotec was here last week and replaced my tube. When the tech was here he ran one of those $1000 power meters on my machine and his first reading was 98 watt the second was 103 watt. I just ran my mahoney meter and got pretty much the same reading. I am happy i spent $100 rather than $1000. For me it is working just fine.

Don Corbeil
05-07-2016, 10:24 AM
What I'm looking for on my 300 is the key press/sequence to hold a steady full power beam for as long as you hold the key for testing purposes. The rep showed me this when he tested mine at setup. but I've since forgotten :rolleyes:

TAMI WILSON
05-07-2016, 11:49 AM
it is the shift arrow and the one right beside it it points down then left. you have to use magnets to lock out the lid though. with my mahoney meter i had to hold for 17.5 seconds. the 300 only pulses for about 12 so i had too quickly press it again

Don Corbeil
05-07-2016, 5:08 PM
it is the shift arrow and the one right beside it it points down then left. you have to use magnets to lock out the lid though. with my mahoney meter i had to hold for 17.5 seconds. the 300 only pulses for about 12 so i had too quickly press it again

Ah, that's it, the dual button press. I also realized that I had to go into JC settings and make sure the power pulse setting was at 100%
Thanks Tami for the reminder.
All is good, tube is putting out just shy of 87 Watts.

Very happy to have scored a Macken digital meter & probe for $150! :)

Travis Reese
05-24-2016, 3:51 PM
Don, I found the same power meter you ordered listed by the same seller you ordered from. I was looking at about the time you started this thread. I was worried maybe it was some kind of scam since you had obviously bought the meter the seller had listed. He told me that he had a second one and thus the new listing. I too was worried about the probe descriptions since they didn't correlate to anything on the Macken site. Apparently what the seller was putting in the auction description for the probes was actually the calibration data, not the probe model. I ordered this second one he had listed. It finally arrived today with two probes for measuring 20w-100w lasers. Anxious to see how well it works.

Travis Reese
05-24-2016, 7:30 PM
Finally got home and tested this thing out. I have an EFR 1200CL laser tube in my machine. It's rated at 60 watts nominal 70 watts max at 22ma according to the manufacturer's web site. The people at Rabbit obviously did a nice job of setting up the machine since at 100% power I'm reading just over 21.5ma on the ammeter I put in. I've read where some are set such that they're overdriving the tube at 100%. Being that the power meter I got came with two probes I was able to test one probe against the other. I wrote a program that moved the head at .1 mm per sec on a 2mm line to give me 20 seconds of exposure. I timed it to be sure it came out right and as near as I can tell it's 20 seconds on the dot which is what the meter requires. The first probe read 71.8 watts and the second one read 71.7 watts. At least their seems to be some consistency. I think this will be a very handy little tool.

Don Corbeil
05-24-2016, 8:41 PM
Finally got home and tested this thing out. I have an EFR 1200CL laser tube in my machine. It's rated at 60 watts nominal 70 watts max at 22ma according to the manufacturer's web site. The people at Rabbit obviously did a nice job of setting up the machine since at 100% power I'm reading just over 21.5ma on the ammeter I put in. I've read where some are set such that they're overdriving the tube at 100%. Being that the power meter I got came with two probes I was able to test one probe against the other. I wrote a program that moved the head at .1 mm per sec on a 2mm line to give me 20 seconds of exposure. I timed it to be sure it came out right and as near as I can tell it's 20 seconds on the dot which is what the meter requires. The first probe read 71.8 watts and the second one read 71.7 watts. At least their seems to be some consistency. I think this will be a very handy little tool.

Travis, glad you were able to pick one up, too (and two probes!). Sounds like you are also getting consistent results with yours. All in all it was a great find and I'm quite pleased. Now and then some great finds pop up on ebay, but it takes a lot of due diligence to minimize the risk.

Travis Reese
05-24-2016, 8:49 PM
Yep, I was pretty skeptical but he responded that he had two of them and the one I was bidding on was the last one he had. I took a leap of faith. He had good feedback.

Scott Marquez
05-27-2016, 8:42 PM
I got a chance to use my new Mahoney meter, I had to make a holder for it, which was pretty basic but gets the job done. I ran multiple tests which gave me a chance to trend my power out compared to percentage called for. The photo of my readings was just the beginning, I think I ended with about 15 readings.
Scott
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