Posts Tagged ‘Lighting’

Like the previous reviews of light meters, I am restricting this review to affordable temperature meters I have direct experience with in actual project work. Anyone who works with or applied LED technology should consider investing in some form of reliable temperature meter to test results of either products in development, or product performance in the field. The Achille’s Heel of solid-state technology is its susceptibility to failure and degradation from operating at high temperatures. This extends beyond the LED into the driver and power supply components, which are often placed under stress from fixture packaging or location near heat sources. The first issue that a manufacturer will raise when facing a field failure, will be the temperature the fixtures were operated in, either caused by the product design, or the physical application, heat kills LED products. That said, just like photometric test equipment, laboratories and large engineering departments will spend many thousands of dollars on test gear, and calibration services. That’s great if that is the focus of your business. For the rest of us, especially those in small business, the costs of test equipment must be weighed against the myriad of other tools and expenses. So, the question becomes, can one keep the costs low and still get reliable results. The following is an attempt to provide some insight into this, and show solutions I have found to be reliable after several years of using various products with varying degrees of satisfaction.

The Basics First. There are a couple of fundamental issues to get out of the way. Temperature measurement requires understanding of the elements of any thermal pathway from heat source (LED, Driver, Power Supply), to the environment. The illustration below shows how there are several layers involved, each presenting an interface that acts like a resister to heat flow, very similar to fluid dynamics. Each resistive layer not only blocks flow and creates a temperature differential from one layer to the next, they also create a resistance to measurement of the components in question. If this is not recognized, measurement results can be quite inaccurate and misleading, which is counter to the purpose of owning and operating any test equipment. A lighting system may have several layers to consider, being aware of this and what that means is important in attaining accurate enough results for use in field and design process applications.

This overly simplistic diagram shows how heat generated from a source  passes through resistive layers that must be factored into temperature readings to appraise how hot the source is actually operating at.

This overly simplistic diagram shows how heat generated from a source passes through resistive layers that must be factored into temperature readings to appraise how hot the source is actually operating at.

In addition to the layers of resistance between a source and the ambient environment, when considering thermal measurement, is both the resistance of the surface being tested, as well as its emission coefficient. This is a factor of how effective a surface is in radiating energy from the material itself. Materials with low emissivity (low emission coefficient) will run hotter, simply because the surface is not releasing thermal energy contained within the material itself. Knowing what this value is is critical when taking temperature measurement, especially when using infrared non-contact type meters, which are very susceptible to error from differences in surface emission characteristics.

Types of Meters. For most applications there are two types of sensor technologies. The first is contact based, which means making direct contact with the material being tested, by gluing, clamping, or pressing a probe onto the surface to collect a measurement value. The second is infra-red non-contact sensing, which is simply pointed at the surface, usually with some form of guide laser of visual image to show where the meter is pointed. Both are easily obtained for just a few hundred dollars, to several tens of thousands, so the choices are infinite.

Infrared Meters. Infrared meters are in many ways just light meters tuned to a narrow infrared spectrum. By measuring the amount of IR energy present on a surface, these meters deliver a value, calculated by the meter’s computer based on field of view and distance from the object. While tempting due to their ease of use (point and shoot), they produce highly unreliable results unless the operator understands that the surface of different materials produce decidedly different temperature readings, even if the surface itself is the same. For example, black anodized 6061T6 aluminum has an emission coefficient of close to .97, while raw aluminum of the same allow, without the anodizing, has a coefficient of less than .50. That means the raw aluminum object will appear hotter than it actually is to a meter with no means of changing calibration to reflect this difference. Since the range of materials and state of surface roughness, color, reflective properties varies widely, IR meters are generally not reliable enough for field or lab work. The exception to this is when other temperature measurement methods are in use to establish a baseline or calibration point, where the IR non-contact readings can be used for intermediate quick-checks in-process of test projects.

The Control Company 4477 is a simple laser guided IR meter. It works fine for simple tests, but does not have a means to accompodate variations in emission characteristics of the surfaces being measured, so creates odd results at times.

The Control Company 4477 is a simple laser guided IR meter. It works fine for simple tests, but does not have a means to accompodate variations in emission characteristics of the surfaces being measured, so creates odd results at times.

Control Company 4477 Traceable Digital Thermometer
This small handy $65 IR test device works fine, and has proven to deliver accurate results against much more expensive equipment, when the emission coefficient is assumed to be 100. There is no way to set the device up or change what it uses as an emission coefficient, so this produced odd results at times, causing me to look deeper into why. The first instance was testing an aluminum fixture with a cast head and extruded body. The contact meter and touch-test indicated the head was much hotter than the extruded body, but the IR meter said exactly the opposite, an error of significant proportions to cause me to rethink use of IR meters of this type beyond spot checking where emissivity could be eliminated as a factor.

The Fluke VT04 is a visual thermometer with added features that make it a solid IR temperature meter in a wide range of applications, at a very low price.

The Fluke VT04 is a visual thermometer with added features that make it a solid IR temperature meter in a wide range of applications, at a very low price.

Fluke VT04 Visual Thermometer
The Fluke VT04 is not a thermal camera, although it produces images appearing very similar. At around $750, this is not going to be in every briefcase, but it does offer a significant improvement and far more valuable information than a simple handheald IR meter. The critical advantage of the VT04 is in its including a method for entering emission coefficient values. This removes the variable that causes erroneous readings with other IR meters without such feature. The VT04 is a visual camera based device, which allows you to see the product being tested, with various degrees of thermal coloring overlaid, from none to full IR. I’ve found this very handy when testing a product as it warms up, providing an image of the heat expanding through the product, and comparing that to similar readings in different ambient environments or uses. I also use this meter to locate hot spots on fixtures, which I then attach contact probes to, should there be an indication of a problem worthy of additional investigation.

This simple report created using the Smartview software that comes with the meter shows the low res photo and thermal image overlay the meter produces. Note that their is only one temperature reading - in the center. However for the purposes it is used for, this is sufficient.

This simple report created using the Smartview software that comes with the meter shows the low res photo and thermal image overlay the meter produces. Note that their is only one temperature reading – in the center. However for the purposes it is used for, this is sufficient.

The meter can also be connected to a PC to create reports, fine tune the image and its thermal image layers. As far as infrared meters is concerned, this is a decent device for the money. However, what it teaches is that this type of measurement (non-contact) requires spending several thousands of dollars to be truly accurate. True infrared cameras include interpretation software, higher end sensors, and greater resolution to deliver better results. However, when testing them against the VT04, and surface probe data, I found that when measuring objects with multiple materials and emission coefficients, the meters all produce inaccurate results from one material to another if the materials have a greater than a few points difference between them. For this reason, regardless of how much is spent, IR meters are either too expensive and/or too imprecise for use in light fixture testing.  In my own application, the VT04 is used for visual reporting, or to spot check known product performance, compared to prior results, or in different ambient environments, where the baseline has been set using contact sensors. In evaluating wheter spending several thousand dollars on a FLIR product (the leader in IR cameras), I concluded that the money was better spent elsewhere.

Contact Meters. While there remains an issue of thermal resistance between the surface being tested and the thermocouple probe, and to a lesser degree emission coefficient effects as well, connecting a thermal probe directly to the surface of a product. One cannot forget that to some degree, testing anything by touching it in any way does impart a certain amount of impact on the results. For example, attaching a probe that dissipates energy becomes part of the thermal path, which reduces the measured temperature. However, this is somewhat rare for the majority of testing of lighting products, either in a lab or in the field. To connect to the fixture, there are many different types of probes available. I use ring probes that can be screwed down, bead probes which are usually glued to a surface with thermally conductive adhesive (don’t forget the resistance factor when taking measurements here), and blade probes that can be trapped under a heat source (can also cause issues with thermal path efficiency, so be careful).  Many multi-meters include a thermometer capability in them, requiring that one simply purchases the appropriate probe and adapter to start measuring. However, taking one temperature at a time is a long process. I’ve found that no less than two channels is needed, and use four regularly in project work. The drawback of course is having to place the probes, either on surfaces, or inside the fixture, to gather the necessary data. However, when the goal is to understand what’s really happening within any system, this is the best and most reliable approach.

The Amprobe TMD-10  is a simple 2 channel meter that uses either K series or J series probes. A great basic level meter for those needing accurate readings of one or two points.

The Amprobe TMD-10 is a simple 2 channel meter that uses either K series or J series probes. A great basic level meter for those needing accurate readings of one or two points.

Amprobe TMD-10 2 channel thermometer
This is a very affordable little meter at under $125. It provides readings in two channels, allows use of any popular style of probe, is compact, and easy on batteries. In comparing this to other meters, I have found it to be just as accurate as high end devices, so have no problems using it to extend the number of test points when my other multi-channel meter is used. The readings can be in either C or F, the high and low settings can be retrieved, and the intuitive simplicity of the package just makes it an easy go-to device when all that is needed is a quick result with little fuss. Not much more to be said here. The simply works well, and is easy to set up.

Keep in mind that when connecting any probe to a surface, thermal resistance can create errors in the results. Thermal paste, and adhesives are best applied thick enough to  eliminate gaps and air between the probe and surface, but thin to avoid losses through the interface material.  I use arctic silver pasts and adhesives for this, as they produce the best thermal transfer. The additional time a thermal epoxy takes to set up results in better results than instant adhesives. However, CA instant adhesives are commonly used, but can produce poor results. Another method of attachment is aluminum tape, which produces an instant and easily removable connection. The trick is maintaining solid contact with as little material between the probe and the surface as possible.

The Reed SD-947 has 4 channels + autmatic datalogging, making ti a great lab companion, while still being small enough to be used in the field.

The Reed SD-947 has 4 channels + autmatic datalogging, making ti a great lab companion, while still being small enough to be used in the field.

Reed SD-947 4 channel datalogging thermometer
When the task at hand requires collecting data from multiple points, over a length of time, having a meter than can collect data automatically is a must. This meter is not only accurate, but is less than $250, records 4 channels of data on an SD card. It can use vertually and type of probe, including J, K, R. E. T and S, so finding the right setup is just a matter of shopping around. I generally use K probes, as they can be purcahsed anywhere, and work with the two meters I use, as well as the adapter I have for my Fluke multi-meter. The meter can be setup to take readings at any interval desired, recording the information directly in MS .xls format for evaluation and report generation.

I have found that programming the meter can be a bit fussy and painful. The menu system is a bit clumsy operated from the keypad. However, if the instructions are in hand, there is no issue with getting the job done, and once set up, it remembers after power down, so the most common setup remains in place. There is also a feature to see T1-T2 temperature that allows direct comparison of two probes to one another with a single button press. While this seems meaningless, it’s very hand when checking thermal resistance from one side of a material to another, such as through a thermal interface material (TIM).

For the money, I have not found a better device for in-house thermal testing. I’ve used in in field testing of products, in-house lab testing, and during photometric tests. Usually, the probes are set up to measure the LED at some contact point, the driver at an identified thermal contact point, the fixture body and/or lens, depending on how complex the product is. In cases where I need to include two more points, I employ the Amprobe meter as an auxiliary, which works fine if these points do not require data logging.

Final Notes
As LEDs become more common in the market, there will be greater instances of issues emerging from temperature effects on product performance. This includes simple application of retrofit lamps, where high temperatures cause driver and power side failure rapidly, to indoor linear products trapped in restricted airflow of coves and architectural details. Testing products is critical to identifying issues before they become failures.

In my own product, Tasca, we’ve used temperature tests to refine the product and increase its performance. By adjusting components, light output has increased over 25%. Further, through testing of the product in elevated ambient environmental conditions with restricted ariflow, I now know I am producing a reliable product for virtually any space it might be used, from the cold of winter to the extreme heat of a shop in Arizona.

Temperature testing does not require massive expenses, as the products reviewed here show, but it does require a little effort in researching and understanding how the materials, surfaces, and thermal interfaces between components, and between surfaces and the meters sensors (contact of non-contact) in order to avoid errors in the measured results. This comes from digging into the topic in some detail, which everyone in the modern age of lighting should do anyway, and experimentation to see for yourself how these devices work.

For anyone interested in saying hello in person, to knock ideas around, or just tell me what you think of things, meeting up at a conference is ideal. Since I try to bring original content to each venue, the time it takes to put a presentation together is enough that I usually limit the number of presentations to 3-5 a year. This year is about over, but I do have 3 more to go on the schedule, for anyone interested.

The next outing is the LED Show, which is usually held in Las Vegas, but will be at the Los Angeles Convention Center this year. I’ll be there in the afternoon of the 17th, the morning of the 18th, and for a short time after the presentation session on the 18th. I’ve been presenting at this show for several years, and always have a good, meet new people, and learn a few things. Hope to see you there.

This is the presentation brief for the LED Show, Thursday September 18

This is the presentation brief for the LED Show, Thursday September 18

The next presentation is for members of the Chicago Lighting Club, I’ll be presenting the evening of October 20th. The topic is going to be held back as a surprise and fun for the designer types out there.

Directly following the Chicago Lighting Club I will be presenting at the LED Specifier Summit in Chicago. This is a great program and the one day format makes it perfect for busy designers to get in and out. Chicago is closer to home than most venues, so if you are in our neck of the woods, stop in and say hello.

Spec sum

I will be presenting at 2:00PM in Ballroom E

I don’t have any further planned public events on the calendar for the remainder of 2014. I do have presentations prepared on various topics for private presentations, both on a consulting basis, and for use in training sales, marketing, and design members about lighting, the lighting market, and solid state/LED technology on a practical level. If you have something in mind, let me know, we can create custom content as well.

After reviewing a range of different metering choices in actual use, I compiled a summary of findings, as well as my own personal subjective ratings of features and overall utility as a lighting professional. This chart is the collection of all findings in a simple comparison table for those who find this useful (like me):

The Meter Comparison Table in .pdf format.

Note that all of the meters tested were shown to deliver accurate results when testing LED products, as well as conventional lamps. This is not always the case. Many older meters do poorly under LED light sources, either delivering unreliable results, or unstable readings. One example of this are the obsolete Minolta meters manufacturer before LEDs had entered the market. These often deliver CCT results that are far enough off more current meters as to render them essentially useless. Also, some LED products flicker at a frequency that creates moving readings, which never stabilize enough to be readable. The meters I have that exhibit this behavior were excluded from review completely, for obvious reasons.

This is by no means a comprehensive review of all the meters available to designers and engineers. I could have scoured web sites and pulled down more data to include objectively from indirect information. However, that was not my intention, and like the results I get from testing actual products against published data, there is no substitute for directly using and testing any product. The problem for most of us is that testing every option before buying is just not possible, or practical. So, with that in mind, and reflecting the fact that I have both collected more than my share of instruments and put them to use, and have had access to others purchased for and with customers, I offer the reviews as they stand. In this, simply regurgitating what I get from web sites would only pollute the results, as anyone can do that, as that is how I came to purchase those products I have, for both good and bad results. I hope that this this is of value to those making your own decisions, hoping to avoid some of the redundant purchasing decisions I have, that has led to having this many meters collected to review.

That all said, if anyone has a meter they feel was unfairly excluded here, that would like to be added, I offer this. Send me the meter and give me a few weeks time to play with it, and put it to use in tests we are completing on a regular basis. This includes whatever software is required to create a complete picture of the product in actual use. I’ll add what I find to the meter reviews by adding an entry for the specific product, and update the summary comparison table before returning the meter – unless I find I can’t live without it and find myself compelled to add to my collection – which we can discuss at the time.

This is the Lighting Passport Flagship set. Includes case and accessories in a neat package.

This is the Lighting Passport Flagship set. Includes case and accessories in a neat package.

I first saw this device at Light+Build Frankfurt last fall. I was impressed enough to find one added to my collection of tools. The Asensetek Lighting Passport is a unique product in several ways. First, it is essentially a meter head (where the cost is), coupled to an iOS or Android device that does all the computational and display work. The lighting head has a nifty slide action receptor cover, so there is nothing to come off or get lost in a bag or pocket. The measurement range is as broad as any of the other spectrometers tested here, plus some. Not only does it produce the expected spectral power distribution, CRI, CCT, CIE 1931 and 1976 coordinates and illumunance in lux and Fc, it also delivers CQS values. There are several additional data points worth singling out:

  • Du’v’ value. This is the missing piece of the CRI value we have always needed and were never provided. This tells you whether the light source is above or below the black body line. A positive value indicates the source will appear on the yellow/green side, while a negative indicates a tint of magenta will be present. When you put two sources side-by-side of the same CCT and CRI/CQS, you will see these differences clearly. Now, with the Du’v’ value, the difference will be quantified and usable in future comparisons when you don’t have both sources in the same room at the same time.
  • S/P (Scotopic/Photopic) value. This is the value that will drive future lighting decision making. This indicates how well a spectral power distribution satisfies both the scotopic and photopic visual response curves of the human eye, which combine to deliver mesopic vision, and is the center of most current thinking in explaining why we find one source more visually stimulating and clear over another. This is also the value described by the IES in TM-24 13, where the application of S/P ratios can be used to reduce energy use, by taking advantage of the dynamic advantage of high S/P ratio light sources ability to generate increased visual acuity at reduced illuminance levels.
  • PPFD, or Photosynthetic Photon Flux Density. This is the amount of light in umol/sec meter sq. in the spectral distribution (red and blue peaks over human vision in yellow green) that is used in lighting of plants. While not everyone will find this useful, when you need the data, this meter delivers it. Its also an interesting value when looking at how an artificial source and daylight compare, but that’s for another discussion.
  • FWHM color value. This is an interesting value that shows the width of a products light output to 50% of its relative power in wavelength. This is an indicator of how broad the total power distribution is, and is very interesting when comparing two sources to one another.
  • Peak and Dominant wavelength. Peak wavelength tells you where the highest output of a product is centered (in color), while dominant wavelenght tells you where it sits in CIE coordinate positions.
  • ANSI bin and CIE McAdam Ellipse values. Based on a preset standard value for the CCT a source is nearest, you can see where the measured product sits within the standard ANSI color bin, and how far off in McAdam steps it is from the CCT standard center. These are excellent tools in comparing two sources to one another of the same CCT and CRI, and along with the Du’v’ value will provide insight into what to expect in application of the products, in relation to color differences between two products.
  • Multiple source comparisons and multiple readings of a single source. The Lighting Passport allows multiple readings to be taken and compared, or collected into database. This provides direct comparisons on the meter itself of two products to one another, or of multiple readings taken in sequence within one test session. This not only allows comparisons to be made objectively on all metrics, it provides a tool for evaluating color shift over light distribution patterns. For my own use, using this meter on a goneometer rig means I can not only collect the illuminance data necessary to define light distribution, but see how the color values shift throughout that light pattern.
  • Light transmission accessory software. This small utility program is great for evaluating light transmission of materials, generating a simple report of the materials properties in both total transmission, and spectral transmission. This is a tool that every lighting meter used for design should have.
The range of information available to view on screen is excellent, clear and easy to read.

The range of information available to view on screen is excellent, clear and easy to read.

So, with that all covered, one would have to say that the product is impressive, and spot on target for what lighting professionals need in a portable and small lab environment. But, that would be missing some even more interesting features of the Lighting Passport that puts it head and shoulder ahead of the rest. Like this:

  • Separate metering head operated by wireless (Bluetooth) connection. The small head size means not having the meter body height involved in the placement of the sensor, which can be an issue in task illuminance readings, where the light source is inside 36″ of the target surface. In all the other meters with an integrated head, the body height of the meter gets in the way of gaining an accurate measurement. The Passport includes a small stand attachment that allows the meter to be set where you need it, then stand back to eliminate the influence of being in proximity of the measured result.
  • Works with ANY iOS device and Android 4.4.2 device, identically. That means phones, tablets and Pod music devices. So, if you already have an iOS or Android phone, you don’t need anything but the meter head, which slips into a pocket, to take for on-site measurement. This also means that use of a tablet sized device allows the meter and its output to be viewed easily by several people in a room, even projected onto a video monitor. In my case, I’ve connected the sensor head to my Samsung Note 3, and taken readings in a room with people viewing the results on an HDTV connected to the Note 3’s USB connector. This takes education sessions, product evaluation sessions, and general discussion and presentation to a level no other meter can match. Here’s another neat feature of this product – the interface software is open platform based, which means those with the need to create a custom interface for specialty evaluations have that available to them. This also means that updates to operating software through Android and iOS app outlets will make keeping the product current will be far easier than anything proprietary products can match.
Separating the meter head from the display is an outstanding feature that allows it to be used in a wide range of applications, and not interfere with readings.

Separating the meter head from the display is an outstanding feature that allows it to be used in a wide range of applications, and not interfere with readings. The little clip to the left attaches the head to any tablet device with a secure clamp feature.

The lighting head is compact and when mounted on its provided stand, stable for remote measurement. It is also the only part you have to carry with you to a job site, should you already have the software installed on a smart phone.

The lighting head is compact and when mounted on its provided stand, stable for remote measurement. It is also the only part you have to carry with you to a job site, should you already have the software installed on a smart phone.

The meter and its design is impressive enough to be a reason to consider it, and is very usable as a stand alone. However, on top of this, the Spectrum Genius software creates an expanded opportunity for evaluating all of the collected data in a single screen, and compare sources, or multiple readings at once. This adds a layer of utility to the metering system that really enhances its use for those doing a lot of work in evaluating application results or products for consideration in specification. It also generates very nice reports, exports data into spreadsheet worthy data sets for use in other calculations. In my case, I export the data set from multiple reading sessions to create photometric reports that are used in conjunction with the spectral reports to create all of the same data one gets from an LM-79 report, in-house, of any product I can get my hands on. That means I have been able to compare LM-79 reports provided by manufacturers to test results of product samples – with interesting results. I can also provide preliminary LM-79 evaluations of products in the design phase for customers, before they  are completed for final testing at an independent accredited lab. No more ugly surprises and re-testing issues when a product does not perform as needed or expected.

The Spectrum Genius software puts everything in one place, making evaluation quick and easy to see.

The Spectrum Genius software puts everything in one place, making evaluation quick and easy to see.

The Lighting Passport can be found in the market under the brand name Asensetek, and is sold in the USA by Allied Scientific Pro. The prices are wide open, you can order them on line, and with a range of between $1,500 to $2,500 for the meter and its attachments, plus software for free to $500, this package delivers a massive bang for the buck. This pricing is less than some of the high end white-light illuminance meters on the market, while delivering far more information. The product can also be calibrated, so can be used for precision applications and  other uses where it is important to have backing for the data collected.

Printing a report from the software to provide to customers or store as a record for comparisons is a nice feature

Printing a report from the software to provide to customers or store as a record for comparisons is a nice feature

In conclusion, I use the Lighting Passport as my go-to meter choice, and have found very little to complain about. It’s not perfect:

  • The software is a little glitchy in its display, but not so much that I find it an issue.
  • The software also creates a graphic error when creating a report using CQS, as it overlaps the data from R values with the Q values from Q7 thorugh Q15, which is truly annoying. I’m hoping this is resolved in future software updates.
  • The software also uses a dongle for security, which some will hate. I like it, as I have the software installed on both my laptops and desktop, and can move the dongle between them for use anywhere. others will find the tether objectionable I am sure.
  • The transfer of data from the meter to the software is through email or iTunes over wireless, although you can upload the data by file explorer in Android devices. This is fine with a smart phone, and works just fine with the iPod device provided in the Lighting Passport Flagship set (with wireless availability). It would be nice to be able to connect directly from a desktop through wireless to download stored files, but this is not a serious problem, and more an issue with the devices themselves – separate of the meter system. I find no compelling need to operate the meter from a desktop, as the remote head and hand held ergonomics of the data collecting device are just fine. In a lab space, use of an Apple mini-pad or other tablet device works quite well, and eliminates the need to have a computer dedicated to lab duty where it sits unused most of the time.
The package of components are well thought out, and well designed. Quality is very good.

The package of components are well thought out, and well designed. Quality is very good.

Overall, for anyone looking for a portable, high quality spectrometer/illuminance meter product, the Lighting Passport is going to be hard to beat. At its current price, I would say impossible to beat actually. More on this from Allied Scientific Pro More on the Spectrum Genius Software

We have now entered the modern era, where meters are available with a dazzling array of features, at a fraction of the cost once commanded. In this case, the UPRtek MK350S, available also in a lesser featured, and lower cost MK350N version, produces amazingly beautiful results with little pain in the wallet or the head from learning to use it. You may find this also sold under other brand names, such as AIBC, or sold through outlets such as Allied and Ikan. I first saw the MK350S at Light+Build in Frankfurt. A customer of mine also saw them, and was so impressed, he purchased one and has allowed me some time to play with it and in preparation of building up a test lab for his company.

MK350S package

MK350S package

The MK350S comes with all the parts necessary to put it to work. With a bit of minor assembly, insert the battery, slide in the data/wireless card, charge it up, and its ready to go. The touch screen interface is a great feature, as is having the results readily displayed on the device itself in full living color. Their is a camera function that not only allows a picture to be associated with the readings taken, but assists in aligning the sensor when readings are taken.

This meter can deliver the entire collection of desirable architectural lighting results (with a couple of interesting exceptions we will cover in a moment.) The output on the screen can be configured to show:

CCT
CRI
Spectrum view
CIE 1931 view
CIE 1976 view
LED Bin position (within a standard ANSI bin for the CCT reading)
Footcandles and Lux
Dominant and Peak wavelength
Comparison of two light sources
Associate a photo to a meter reading
Purity

The data can be stored on an SD card for use within the companies basic software, which duplicates the presentation of the device itself. Overall, the product runs in the $3,100 range at the advanced level, while the MK350N can be hunted down for around the $2,500 mark. The extra $600 produces several nice additions, particularly the lack of CRI and Purity. Further, the MK350S includes wireless communication for control of the device, where this is an add-on the the MK350N, which will bring its cost closer to the MK350S level, and still be missing the CRI function. Here is a link to a comparison of the two MK350N vs. MK350S.

mk3503

The range of delivered outputs from the MK350S is impressive

I found the product an exciting tool. Its difficult to resist walking around taking readings all over the place and looking at the results. It’s great having this all in hand, without cables connected to a laptop, and a display bright enough to be seen in daylight conditions. The meter fits well in the hand, and goes a long time on a charge. Overall, this is a great new step forward in bringing accurate, relevant lighting data to specification level decision makers and evaluators.

LUX.G image from AIBC web site

LUX.G image from AIBC web site

There is another unique feature provided in the MK350S, called LUX.G that generates a colorized brightness ratio image of a space to illustrate brightness patters. This false color imagery helps the user see the brightness patterns more clearly, and is rather interesting. Not sure exactly how useful it will be, but it is certainly something to look at.

This all said, I have a few nits to pick with it.

No CQS. With CRI under attack, and likely to be replaced soon, likely with the CQS or other similar system, I wonder how they will deal with the new standard when it emerges, or will this be a matter of having to replace the product itself?

No P/S Ratio. It seems an easy addition to include the Photopic/Scotopic ration function, considering how this is becoming a topic of discussion for future approaches.

No McAdam Ellipse evaluation in the bin function. With the data existing in the system as it sits, there is no reason this comparison could not be included.

Not wild about the software/wireless registration loop. The company makes every new user jump through a few hoops to get their software up and running, and the wireless card to work. The real problem here is that the wireless card must be functional to access the memory card for storing data, so until that’s done, there is no way to get the data from the device anywhere else. But that’s okay, since the data is useless without the software, which also requires a registration loop.

Integrated display on top with fixed light sensor is not ideal. The fact that the sensor is permanently stuck in the end of the meter, and the display is on top, means that in lab or tripod mount uses, the meter must be connected to a computer to see the results. Further, the sensor at the end of the meter means reading some angles must be done blind, then read, which renders the camera assisted aiming moot. While we’re on that topic, the camera position on the head is enough offset of the sensor, that measuring close up objects is a bit odd, requiring you offset what you see to get the sensor properly centered. It would be a nicer device if the sensor head popped off for hard-to-read, tripod, and lab application.

These are all minor issues in the bigger picture, and will likely be smoothed out as the product is applied over time. This is a level of performance, and superior in the GUI over much more expensive systems, like the Minolta CL500, whose display is poor, or others where connection to a computer is necessary to come even close to what is displayed in this handheld device.

More on the MK350S from UPRTek and from AIBC

To compliment a standard light meter, which does a fine job collecting illuminance information, I sought a low cost solution to evaluation of color data, specifically CCT, spectral power distribution and CRI. My goal was to find a product under $2,000, that could be calibrated, that would deliver me color information simply and without a large amount of special technical effort. I found that in the Mightex CCD Spectrometer. At a base price under $1,700, it fit the budget nicely. Of course I added a few accessories to it, and paid them to calibrate the meter with a fiber optic mounted cosine sensor, which increased the total invoice to a touch beyond the $2,000 target… However, in the end, I found the results to be exactly what I was looking for – almost.

Mightex CCD Spectrometer

Mightex CCD Spectrometer

The CCD based (same technology as high resolution cameras) spectrometer is that it holds its precision over a wide range of temperatures and for long periods of time before requiring re-calibration. While the software is not as slick as the previously mentioned Orb Optronix SP-100, it is certainly functional, and delivers the information I wanted from it. It calculates CCT and CRI, and presents it in both graph and graphic formats. The spectrometer’s raw data can also be downloaded in a file format usable for evaluation in spreadsheet form.

Connecting the meter to a computer is as simple as plugging in the USB cable, which also provides the power to the unit. I use a fiber optic cable from a cosine correction end attachment, as this allows me to leave the box and its connection to a laptop on a table, while reaching up to ceiling products, or fixing the reception head to a holder for lab testing on the goniometer.

Mightex CCT and CRI screen output

Mightex CCT and CRI screen output

mightex graph

Mightex Graphic output

The output reports are very easy to read, and show all the information I need them to, including individual R values in the CRI calculations, and pertinent color coordinates in both numeric and graphic format. For the money, it delivers most of what much more expensive equipment provides, in a very simple to use and apply unit. The software does take a few moments to figure out. Of particular issue is selecting an appropriate sample rate, sample number, and integration time to create the most accurate CCT and CRI result. This is usually done by experimenting with various settings in the operating software until a smooth spectral distribution curve is created. A smoothing function can also be applied to improve results.

This is not going to be a user-friendly device for anyone who is not familiar with photometric testing using spectrometers. Failing to apply the proper settings creates wildly erroneous results that will be confusing to those who are not familiar with what causes them.

One missing piece that needs mentioning, is that the Mightex does not produce illuminance values in any form usable in architectural lighting. The data can be read in absolute irradiance as uW/cm2,  which can be translated and converted to other forms. I needed this exact data for one customer in the UV light curing business. However, for the most part, the data is most useful in spectral power distribution evaluation as presented without bothering with any such effort. For my uses, other meters provide me the photometric data I need without relying on the Mightex for use beyond color evaluation and performance. Overall, this is a nice tool for those looking to create a low cost lab setup. For the architect, lighting designer, or electrical engineer looking for a portable light meter solution with CCT and CRI capability, it is probably not an ideal solution.

More on Mightex Systems

When it came to setting up a lab with a proper precision meter for collecting and evaluating color (CCT) and color quality (CRI), as well as measuring transmission, luminance, radiance, irradiance, and illuminance of light sources and fixtures, I chose the Orb Optronix SP-100. This was done in partnership with a customer, for whom we set up a complete lab with goniometer we built for the customer, for testing their ongoing products as part of a design services agreement. In time as the customer grew in their own capacity, the entire rig, along with the data processing protocol we developed over several years, was transferred to the customers own facility, where staff was trained to complete their own tests in-house, where this is still in use today.

Orb SP100 and gonio setup

Orb Optronix SP100 and gonio setup

This Orb Optronix is an excellent meter on its own. It includes a laser aiming feature that seriously improves setup accuracy and reduces the time it takes to align the test product with the sensor. The SP100 was very easy to learn, and generated usable data from its first day in use. It did take some time to sort out integration times (time the meter is given to process incoming light before recording a value) and to recognize when the dats itself is in error due to a lack of time allowed, or number of samples per reading was inadequate. This is truly a lab grade product, and the price reflect that focus, placing it at the top end of the budget range (>$9,000 to start), which can balloon for those adding more features, adapters, training and other services.

I would not consider this a product for a consulting firm looking to evaluate lighting products for specification consideration. While the meter itself is a nice size, and exceptionally accurate, its most at home in a fixed lab, operated by individuals knowledgeable and focused on setting up proper test protocols. There is also one missing bit of data from this meter and its software – that is Illuminance  in the form of Lux and/or Foot-candles. Also missing are candella, and lumens. This requires taking the raw data, in other forms, and converting it to these values. In my case, we used spreadsheets to create candella data from illuminance in Lm/M2 then used other programs to convert candella distribution data derived to photometric files, which created the lumen output and other photometric values we needed to relate to architectural use. This is not specifically a fault in this system, it simply reflects the intended purpose of this product to obtain accurate lab level data.  I must qualify that we chose not to purchase the SpectralSuite product offered by Orb Optronix, which produces LM-79 output in proper photometric values, choosing in stead to save the money and do this work ourselves.

The basic software package provided with the SP100 is excellent.

The basic software package provided with the SP100 is excellent.

The software that is included with the SP-100 is excellent in its own right, providing both visual and tabular output for detailed evaluation. The operating process is very simple and intuitive, given a little time to understand the dynamics involved. For setting up a lab in limited space, their were few options within the price range of the SP-100 that would generate the quality of data we collected. However, my first work with this product was over 5 years ago. Since that time, several new products have come on the market that are both better suited to architectural lighting evaluation, and far less costly. Since the SP-100 has been moved to my customer’s site, I’ve moved on to other products to serve the requirement gap the loss of the SP-100 created in my own in-house lab operation. For my own personal business needs, the cost of the software and hardware was a bit more than I was willing to invest, especially when I considered I’d set up my most heavy use customers with their own labs, which significantly reduced demand for testing. As it turns out, advancing technology would not only solve that for me, but deliver new opportunities not possible in 2009.

For covering the range of CCT, CRI, spectral power distribution (with very fine fidelity), luminance, radiance, illuminance, irradiance, x,y and u’, v’ chromaticity coordinates, dominant wavelenght and peak wavelength of any light source, I found the SP-100 is a valuable tool.

More on the Orb Optronix SP-100