June 15, 2015
Most people are taught to think of electricity via the analogy of running water. The volume of water moved from point A to point B is analogous to voltage while the rate which the water flows is like electrical current. Multiply the two together and you have power(P=IxE).
Static electricity is the opposite of current electricity, in that it does not move. It just builds up between two non-conducting materials (like plastic and rubber) and sits there, waiting to discharge (Google Triboelectric Effect). If you have ever touched something and got a brief shock, you have likely experienced static build up and provided the path to ground that discharged that potential energy charge. If you ever touched something and got a prolonged and painful shock, you have probably been electrocuted and may be reading this from the Great Beyond.
Static build-up occurs in environments that are dry. Water molecules help diminish charge build up. Insofar as laboratories are concerned, static is generally not an issue due to controlled temperatures and humidity...but they are not immune. This can be routinely found to be an issue with ill-behaved liquid handlers. Disposable plastic pipette tips have been known to 'hang up' or not eject from their mandrels when humidity levels drop. I have seen tips appear to dance in mid-air, only held to the mandrel by static charges. This is dramatically visible with lower volume (384) tips as their mass is less to begin with and is exacerbated by the use of rubber o-rings on the dispense head mandrels. Rubber, plastic and lack of humidity are the perfect recipe for static cling.
So what can be done? Well, the simple solution is to add humidity to lab. If the lab's HVAC system is not capable of effecting changes, you could place a humidifier near your liquid handler. Just be careful as it is a fine line between adding moisture to the air and saturating your robot. Get a can of Static Guard from your local grocery store. These sprays add moisture (water and alcohol, with minerals and salts removed) and are very effective (albeit temporarily) when sprayed directly on rubber o-rings. Another longer lasting and more pragmatic solution would be to place an ionizing fan right on the liquid handler deck, near your tips racks. These devices add electrical charges to the air (anions, or negative ions) and the fan blows it across your tips which can change the electron imbalance just enough to offset clinging tip issues.
Don't let your labs environment make you retreat from automated assays....wait for it....here it comes...."CHARGE." That just happened. BAM.
Next Blog - Vision Sensors (they can be used for lots of stuff, including pipette tip issues...)
August 7, 2013
New MVS Survey
Oh behalf of HTStec, The LabSquad is pleased to inform you that their latest survey titled "LAB INSTRUMENT SUPPORT STRATEGIES TRENDS 2013" is now underway.
"Proper maintenance of laboratory instrumentation is an important consideration to ensure that lab assets remain available to researchers. Minimizing downtime makes the research process more efficient. A variety of support options are available from original equipment manufacturers (OEM), small third party independent service organizations (ISO), large multi-vendor service (MVS) providers and internal support staffs. Understanding the needs of lab users is essential for service providers to ensure customer success."
If you count on your lab instruments being in 'research ready; condition, please take a moment and fill out this most important survey. JUST CLICK HERE
July 23, 2013
In the last two installments, we talked about simple DC motors and stepper motors. To recap, a DC motor is basically the simplest (think 'Lloyd' from the movie 'Dumb and Dumber') motor you can find. Simply apply voltage with sufficient current and it spins. You can reverse the spin direction by reversing voltage polarity, and you can control the speed by applying varying voltage levels or by sending short pulses of voltage. Stepper motors are a...'step up' (I hate puns) insofar as intelligence goes (think 'Harry' from 'Dumb and Dumber'). By which I mean, you can send them specific (countable) pulses and the motor will rotate in very predictable increments (steps). Steppers are natively 'open loop' but are oftem fitted with rotary encoders to provide position feedback. However...that position feedback is often an 'after the fact' reconcilliation on the number of steps commanded vs the number of pulses counted. It is not a 'monitor on the fly' feedback loop and that is by definition what a servo motor brings to the table.
In the most basic sense, a servo motor is a brushess DC motor fitted with a feedback sensor. The output of the feedback sensor is used to determine the final position of the motor. These devices can be very small (like hobby RC servos) or larger. In general, with increased size comes larger windings which enable more current and greater torque. Depending on the device the motor is attached to, you can expect to see a series of drive reduction gears or pulleys for even greater torque. Unlike hobby servos which have both gear reduction and circuitry embedded within their housings and use potentiometers for feedback, most industrial servo motors require a separate driver or control board that provides motor voltage and also monitors the encoder in real time. The image to the left represents a simple hobby servo which nicely illustrates the feeback loop concept. Both the input signal and the output from the sensor (potentiometer, in this case) are feed into a comparator circuit. Because the gearing is built in and known relative to the gear ratios, the comparator can essentially decide when the motor needs to be stopped in order to achieve the commanded motion (so many pulses should equal so much resistance).
The pulses sent to the motor are generally all the same voltage but number of pulses sent over time is what determines speed. This is called Pulse Wideth Modulation (PWM).
Troubleshooting a servo motor is not easy. If the motor and encoder are separate units, you can apply the rated voltage to motor (disconnect any pulley/belt or linkages first!!!). Encoders are a bit trickier and we will cover them in a future tutorial. You can try some basics like checking wiring connectors or blowing air the encoder to remove dust, dirt or grease. Beyond that...you will need to crack open the case and hook up a scope to see what the pulse train coming from the encoders look like. Most encoders are off the shelf devices and you can Google specs to compare with what you have. This will at least help you zone in on the encoder or the controller/board it is plugged into.
July 22, 2013
Unlike a brushless DC motor which rotates continuously when a fixed DC voltage is applied to it, a step motor rotates in discrete step angles. Stepper Motors are manufactured with incremental steps per revolution of 12, 24, 72, 144, 180, and 200, resulting in stepping angles of 30, 15, 5, 2.5, 2, and 1.8 degrees per step. The stepper motor can be controlled with or without feedback.
Stepper motors work on the principle of electromagnetism. There is a soft iron or magnetic rotor shaft (rotor -= rotate...it spins) surrounded by the electromagnetic stators (stators = stationary...they're fixed locations). The rotor and stator have poles which may be teethed or not depending upon the type of stepper. When the stators are energized the rotor moves to align itself along with the stator (in case of a permanent magnet type stepper) or moves to have a minimum gap with the stator (in case of a variable reluctance stepper). This way the stators are energized in a sequence to rotate the stepper motor.
There are two basic types of steppers-- bipolar and unipolar.Unipolar
- A unipolar driver's output current direction cannot be changed.
- There are two sets of the coils for each phase in a motor.
- Only one set of the coils can be energized at a time.
- Each coil represents one phase.
- Driver's output current direction can be changed. 100% of the winding is utilized in the bipolar drive. That means the two sets of the coils in each phase can be connected either in series or in parallel to become one set of a coil
- Current direction changed from the driver creates another mechanical phase.
- The number of mechanical phases is always twice the number of electrical phases
- Bipolar drivers provide 40% more holding torque than unipolar drivers, but typically run at higher temperatures
For this last reason, proper heat dissipation is important with bipolar drivers. A bipolar stepper has 4 wires and Unipolar steppers have 5,6 or 8 wires. The rotor has a permanent magnet attached to it. The stator is made up of coils as shown in the image to the left. There are eight coils in this unipolar stepper motor. Every coil in the motor behaves as an electromagnet, when they are energized by electrical pulses. For this particular motor, the opposing coils are paired and each pair shares a common wire.You can see that there are five electrical conntections of the PCB (one common, and four to control each coil pairing).
Stepper motors tend to be less expensive than servo motors (more on servos in Part III), and they are easier to control due to the fact that their precise incremental movements do not require posistional feedback. Simply command this 'open loop' motor and the location is predictable. Now, if a pulley attached to motor shaft comes loose, or if a timing belt attached to the pulley were to lose a tooth due to wear, it is conceivable that the device being controlled could act in an unpredictable way (gets lost) and could fail (crash).
Stepper motor control circuits can be viewed with an oscilloscope.You would need to identify the driver chip or indexing controller being used and look at the pulse train (disconnect any pulleys first).with the motor attached. The motor itself can be tested with an ohmmeter. If you have a bipolar motor, place the ohmmeter between the positive and negative input terminals of each winding. The resistance of the two windings should be exactly the same. If not, the motor must be replaced. If you have a unipolar motor, place the ohmmeter between the positive terminal and the com terminal and then between the negative and com terminals. Do this for each winding. In each case, the resistance should be the same for all measurements; if not, the motor must be replaced.
June 28, 2013
Did you ever work with a field service engineer who was just plain awesome...someone who always went above and beyond to ensure your success? If so, you have probably asked yourself ''what would I do without them? ' Sadly, that hypothetical question, all too often, becomes reality.
For any number of reasons (some good, some not so good) people are transient. As the old saying goes, no one is truly irreplaceable, so the best protection vendors can provide for their customers is to ensure that more common procedures are documented. For example, irrespective of who is doing the work, a preventative maintenance procedure should always be the same. Each step, every tool, replacement part, lubrication or adjustment should be captured in a document that can be used to cross train FSE's so that your instruments always receive consistent maintenance.
Whether you are working with a new FSE to support a new install, or existing instrument don't hesitate to ask to see the procedure they will be following. Most vendors won't share all the details, but many will let you have a glance and most will provide checklist that highlights the work to be done.
If a vendor cannot produce documents for common procedures (like a PM). before they commence their work you should be concerned. I'm not saying that you are about to be mis-treated, however how can you be certain that the requisite work will be accomplished if there is no guideline? You wouldn't conduct an assay without a documented procedure and you shouldn't allow anyone to work on your instruments without one either.
If they can't show you 'the book', then throw the book at them!
April 9, 2013
It’s been over 35 years since the movie Marathon Man came out and I still have a fear of dentists. That imagery has nothing whatsoever to do with the topic of this blog, but the title reference was too good to pass up…
Everybody who works in a research lab no doubt has had to go through a mandatory lab safety course or certification. Companies provide such training both to ensure the safety of their employees and processes as well as to avoid future litigation should an accident occur. What is not always as clear is how to ensure the safety of visitors, or in the case of instrument support, Beyond providing lab coats and safety goggles, there are a couple of basic precautions that can be taken to ensure the well being of visitors and support techs;
1) Contact Person – all visitors should have the phone and email info for an employee who has been through a company approved safety training program. Visitors should be required to seek out this person for any concerns they have prior to conducting their work, or in the event of an emergency. Also, make sure you have the techs emergency contact (work and personal) info in the event that person requires medical attention.
2) Disclosure – Make sure you inform the tech of any biological or chemical hazards regarding the instruments. Point out instrument decontamination certificates and give direction on how to dispose of wastes (chem wipes, q-tips, wear items, gloves, lab coats). Also let them know your protocols for dealing with reagent spills or exposure.
3) Evacuation Instructions – Let the tech know how to exit the building in the event of an emergency. In addition to typical lab accidents, in today’s world that could also include fire alarms, terrorist attacks, workplace violence). Point out any per-determined ‘rally point’ once out of the building. Also, let them know how to re-enter the building or sign out if they do not return so they can be accounted for.
4) Facilities Support – Never let a visiting tech hard wire equipment to your facilities electrical junction boxes. If such a need arises, have your own knowledgeable facility personnel on hand to disconnect power and supervise all work. Same goes for plumbing high pressure air lines or water lines.
5) Basic Safety Training – make sure the tech has received basic lab safety training from their employer. Ask in advance for them to bring a certificate of such training, specific to the visiting tech.
With a little bit of extra consideration, it is easy to ensure the safety of lab visitors. And, it your service tech looks even remotely like Sir Laurence Oliver in the photo above, don’t be surprised if he or she incessantly asks, “Is is safe yet?”
March 29, 2013
Things break in the lab. Here’s how to protect your equipment, and what to do when it stops working.
With NIH funding fewer than 20% of the research grant applications received in 2011 (the most recent data available) and little hope for improvement in the coming year, researchers must squeeze what they can from every dollar. For some cash-strapped labs, that means buying used instruments instead of new, keeping equipment running long past its warranty, and jerry-rigging existing lab gadgets that might otherwise be scrapped.
When such equipment inevitably fails, it puts yet another strain on already tight budgets. Researchers facing service calls costing hundreds of dollars an hour may feel obliged to delay repairs, only to find that a service tech may not be readily available. Even in the lab, time is money.
There is an alternative. Lab workers armed with a bit of mechanical know-how and some basic tools can sometimes tackle repairs and problems themselves. Not every repair can or should be handled in-house, but those that can will get the lab up and running quickly and cheaply. The Scientist spoke with equipment repair technicians and core facility directors about the kinds of repairs that researchers can and cannot do on their own, and some obvious, but oft-ignored, steps they can take to avoid problems in the first place. Here are their suggestions.
1. RTFM (READ THE F**KING MANUAL)
Like cars and computers, laboratory equipment almost always comes with a manual (either printed or as a PDF). And, as with cars and computers, researchers often toss those manuals in the trash or “file” them in a drawer. Here’s a better idea: as they say on the interwebz, RTFM. Manuals outline recommended maintenance and cleaning schedules, provide troubleshooting tips, and demystify error codes. (Lane Smith, President and Senior Engineer at Phoenix Technical Services, an equipment repair company that serves the University of Mississippi, suggests storing manuals together in a safe place, or as PDFs in a common folder on a lab computer, for easy retrieval.)
The maintenance suggestions these manuals lay out may surprise you. Rebecca Wood, co-owner and vice president of Southern Medical Services, a medical and lab equipment repair firm that serves south Texas, notes, for instance, that some vacuum pump manufacturers specify in their manuals that vacuum oil should be changed after every use. Yet many researchers reuse the oil until it gets dirty—a practice that could potentially cost the lab big bucks. “If you had a vacuum pump that quit and you sent it in for repair and it had black gunk in the oil, they would say you’d voided your warranty,” Wood says.
2. Clean up once in a while
An ounce of prevention is worth a pound of cure, they say, and that’s certainly true in the lab. Dust accumulates on computer parts, ice accretes inside freezers, and carbon dust builds up inside centrifuges and stir plates. Taking care of these issues before they become problems can save a lab some money in the long run. “If you use a [centrifuge] rotor, make sure it’s cleaned afterwards,” says Craig Folkman, a field service engineer atBioNiQuest Lab Services in Danville, Calif. “Make sure O-rings aren’t cracked, and change them as necessary. If there’s a spill, clean it up, don’t let it sit there.”
For mechanical devices that use brush-based (as opposed to induction) motors, such as vortexers and microcentrifuges, Smith recommends investing in a small vacuum cleaner to clean out the carbon dust. (Smith notes that replacing a worn set of motor brushes is a relatively simple task that researchers can do themselves. For one of his techs to make a lab call would cost $200 for an hour of labor plus the brushes ($20–$50 for a set), not to mention travel time.)
Invest in a can of compressed air to clean computer fans and cables, or tracks on liquid handlers. And clean the air filters on lab freezers regularly (they are usually easily accessible on the front of the instrument). “These are fairly expensive pieces of equipment, and some scientists will have their entire research life in these things,” Smith observes. Cleaning or replacing the filters will keep the compressor working properly and prevent it from overheating.
Another easy bit of maintenance: Defrost freezers regularly. “Try to do it once a year, because you will either do it on your own schedule or on the instrument’s—at 2 a.m. on a Sunday morning.”
3. Establish a maintenance schedule
“My feeling about lab repairs is really trying to avoid them,” says Tim Hunter, Director of the Advanced Genome Technologies Core at the University of Vermont. Hunter recommends lab managers ensure that each piece of equipment be kept on a routine maintenance schedule (often outlined in the operator’s manual).
For instance, in his facility, one worker’s job includes tracking the background signal in the lab’s real-time PCR machine, to make sure the instrument is operating correctly. Another bleaches fluid lines in the array reader between runs to minimize cross-contamination concerns.
Another commonly overlooked task, Hunter says, is defragmenting the computer hard drives attached to lab equipment. Hunter suggests doing that monthly. “[These are] things that people take for granted and just don’t check, but [that] can really impact things when you least suspect them.”
Wood recommends copying and laminating the schedule for each piece of equipment and affixing it on or near the machine, so that everyone in the lab knows what needs to be done, and when.
4. Build a basic lab-repair toolkit
Charles T. “C.T.” Moses, an independent consultant in Framingham, Massachusetts, has been offering seminars on laboratory equipment repair throughout the Northeast since 2004. The handout for his seminar includes a suggested laboratory tool set for taking on most basic repairs (see also: www.chastmoses.com/tools.html). To wit: Flashlight; multipurpose screwdriver (slotted and Phillips); small vise grips, needle-nose pliers, and side-cutter pliers; a small crescent wrench; small clamps; scissors; measuring devices (scale, tape measure, or ruler); small hammer; pocket knife; multimeter; polarity tester (to test electrical circuits); and a lockable tool box.
Other items you might want to have on hand are lubricants (e.g., oil or WD-40), compressed air, a set of American and metric Allen and socket wrenches, a drill, and electrical tape.
5. Try the obvious
When something goes wrong, the most obvious solution sometimes is the right one. So, if a piece of equipment suddenly stops working, make sure it actually is plugged in and that the outlet is working; even in the lab, plugs come loose, fuses blow, and circuit breakers trip unexpectedly.
Smith recommends doing a quick and commonsense “self-assessment.” For instance, if the −80 °C freezer is suddenly warming up, did anyone recently perform an inventory during which it was left open? Ditto for the cell culture CO2 incubator.
Next, see if restarting the instrument and/or attached computer solves the problem. Or, if it is a mechanical device, see if you can identify something obvious, such as dirt in a track or hinge, which might be causing the malfunction.
If the problem persists, write down any error codes or messages you see, as well as what you were doing when the problem occurred. For instance, if an autoclave stops working, where in the cycle did it halt? Also, see if you can figure out where in the instrument the problem is occurring. “The easiest thing to do when troubleshooting is to cut your problem in half,” says Folkman. For instance, suppose your HPLC isn’t working; see if you can determine whether the blockage appears to be between the buffer reservoirs and the pump, between the pump and the column, or in the fraction collector.
Even if you end up having to call in a repairperson, such information can save time (and thus money). “If you have an error message, instead of saying ‘I’m getting this diagnostic
,’ if you can say ‘I tried this or that,’ that makes it easier for us. . . . We can know exactly what the issue is.”
6. First, do no harm
If you do decide to open up an instrument to attempt a fix, Smith recommends following the physicians’ creed: First, do no harm. Put another way, make sure you can put back together that which you have taken apart.
Use a cellphone camera to take pictures of wires and instrument settings so you know where they go and how they were arranged. Moses suggests using a piece of white paper, marked to indicate the front and back of the instrument, and taping screws on the paper in approximately the positions from which those screws came, “so you know more or less how it goes back together.” (Oftentimes, instruments may use different screws in different positions, so this kind of information can be invaluable.)
To do no harm also means to protect yourself, says Moses. That means powering down and unplugging equipment before opening it, and putting your left hand behind your back before plugging it back in and turning it back on. That latter point, he says, is an “old electrician’s trick” that “helps prevent shocking your heart should your repair leave a loose wire inside the machine.”
Deciding what can and cannot be repaired in the lab must obviously be done on a case-by-case basis. But as a general rule of thumb, repairs that are covered in an instrument manual’s troubleshooting section can probably be attempted in the lab, such as changing the bulbs on a spectrophotometer or replacing the brushes on a microcentrifuge. Instruments like stir plates are easily fixed, says Moses—often a drop of oil at the point where the motor shaft emerges from the motor, called the bushing, is all it takes.
Instruments that are under warranty or service contract probably should not be repaired in-house, as doing so might void the warranty. Very heavy equipment, very expensive equipment, equipment with precise tolerances (such as a microscope), or equipment involving high voltages, lasers, and so on, probably should be left to experts as well. So should equipment with obvious charring or burning, Moses says, as these might require special expertise in measuring and monitoring electrical circuits.
7. Know when to call for help
When in doubt, it never hurts to call the manufacturer or a third-party repair company. Smith says his company will often offer advice gratis over the phone, and so will most instrument vendors. “I have rarely come across a manufacturer that will not answer simple questions on the phone,” he says.
In some cases, you can purchase a part, like a hinge or a circuit board, and have technical support walk you through the installation process. But make sure the repair doesn’t cost as much or more than buying new. Moses recommends checking the manufacture date on equipment to see how old it is (and thus, if it makes sense to repair it). Circuit boards and electrical components often contain a four-digit code in the form YYWW. For instance, 9613 means the component was built in the thirteenth week of 1996; 0744 means the forty-fourth week of 2007. Though such information will not give a precise manufacturing date, an instrument obviously must be at least as new as its newest component.
But before you do anything, see if you cannot at least identify what is wrong before calling in an expert. By figuring that out you can give the technician the most accurate information, thereby saving him time and you money. Just as practically, you can learn what to do differently moving forward.
“By opening [up a piece of equipment] you can be aware of what happened and what not to do in the future. We don’t want this to happen again,” Moses says.
Originally Published on March 1, 2013 at: The Scientist.com
February 4, 2013
Although the patent for PCR expired back in 2006 and promised to herald in a new wave of low-cost thermal cyclers, the legal debate over Taq polymerase enzymes continues to make some manufactures nervous about the North American market. Still, the number of new thermal cyclers to hit the market over the last several years has increased dramatically. As the prices for these work horse devices drops accordingly, the justification for service contracts starts to wane. When opting for a low-cost unit with no local service support, some users may be okay with depot repair or flat-out replacement. When opting for higher quality units, many labs are going with periodic maintenance and routine performance rectification (OQ/PQ). Printed reports or recalibrations by the service tech can be incorporated into your lab’s SOP’s but if you are self maintaining, don’t forget to have the data signed off by more than one person, especially if you are doing forensic or clinical work.
Now, let me put my spin on centrifuge support (wouldn’t be a blog without the occasional pun, now would it?). Seriously, it doesn’t matter whether you have a floor mount, bench top or robot-loaded centrifuge, these devices get a lot of use and it is not uncommon to see units that ten or more years old. Motors and bearings don’t last forever so routine maintenance is critical. Additionally, you folks that leave your rotors in the centrifuge and never take them out should have big scarlet letters painted on your lab coats so you can be publicly ridiculed by the service community! Seriously, many a lab tech has pulled a muscle or two trying to loosen and remove a rotor that has permanently bonded with the spindle.
Last on the docket for this posting is microplate reader upkeep and maintenance. Truly, a wide-ranging topic (may have to post separately on this one to do it justice). The three main readers types (modes) are absorbance, fluorescence and luminescence and while some are limited to one mode, others can do more than one (multimode). Of course there are also fluorescence polarization (FP), time resolved fluorescence (HTRF), high content imagers and microfludic analyzers, but for today we will stick with the big three. All three types work on the basic principle of light measurement to detect samples within the wells of a plate. Absorbance readers use a light source, filters and a detector to measure what percentage of the source light is transmitted through the sample. Fluorescence readers are more sensitive and measure the amount of light emitted from the sample, while Luminescent readers have no light source and instead detect a chemical or biological reaction from the sample. Depending upon the specific reader, any number of factors can result in bad data but generally most failures are a combination of optical alignments (emitter, detector, filters…etc) or light source age. Just about every plate manufacturer provides N.I.S.T. traceable “test plates” that can be used to calibrate the device and a number of third-party companies also have more generic standards that can also be used. It seems patently obvious to say, but what is the point of conducting an assay if you cannot say with a high degree of certainty that your detection results are accurate? At a minimum, plate readers should be PM’d once per calendar year and that procedure should include a test report against a known standard. If your lab only has one reader and it is critical to your research, an annual service contract that includes analytical data would be a wise choice.