SMD is a Manufacturer of custom sensor & load cells for multiple applications worldwide. We develop and manufacture custom sensors to solve measurement problems in medical, aerospace, commercial, automation (robotics) and industrial applications.
Nurses work tireless hours around the clock caring for patients, monitoring vitals and assisting doctors with doing the important job of keeping people alive. They are also up against a number of workplace hazards. From medical waste to patient contact, and even desensitization – there are many reasons for nurses to be cautious while on the job.
What is Alarm Fatigue?
One such issue, alarm fatigue, is a very real problem in the industry needing immediate attention. This occurs when important medical staff, in particular nurses, become so desensitized to the noises going off all day in their environment that they actually fail to react promptly or at all to important beeps and alerts.
In other instances, the alarms – which typically are going off several hundred times a day- will randomly fail, and if that happens in an instance where a heart attack or other major medical event is occurring, the end result can be deadly.
Why Nurses are at Risk
This is further compounded by the fact that many of the telemetry monitoring devices sending wireless alarms to a central nurses station are so sensitive they go off throughout the day even for “false alarms” like a cough, low battery, or sudden movement. Over time, nurses start to “tune out” sounds they are familiar with or that might not be “important” at the moment.
In fact, according to research, 72 percent to 99 percent of clinical alarms are false. However, patients requiring immediate medical assistance left to wait for a response from a nurse due to any of the above-described scenarios can lead to penalties, fines and worse.
An NPR interview with reporter Liz Kowalczyk, who wrote a series on this topic for the Boston Globe, says most nurses acknowledge the issue is something that needs to be addressed and recommends that monitors and systems used in the medical setting be improved upon and developed to deliver less false alarms and more accurate notifications for staff.
Sensors Offer a Solution
That’s where we come in. At SMD Sensors we build customized, reliable sensors that operate within set parameters to provide critical details in the right format, at the right time.
Sensors play a key role in the safe operation of any medical device. Our engineering and design team will work with you to get a full understanding of your device and ensure that every possible failure mode has been considered, including those that could cause the false positives that contribute to alarm fatigue.
Using our proprietary bubble generation system, we can calibrateeach of our bubble sensorsto a specific customer-defined bubble size range. Not only are they guaranteed to alarm when a specific large bubble size passes through them, but we can also ensure that no small “nuisance bubbles” that would be considered false alarms are detected. For example, a common calibration on our A240 Bubble Sensor is to always detect bubbles 2 microliters or larger and always ignore bubbles 1 microliter and smaller.
Further, our custom occlusion sensors or noninvasive pressure sensors are used to detect occluded tubing that can lead to a dangerous situation for the patient. Using miniature load cells for occlusion detection is superior to ultrasonic occlusion detection because it significantly reduces the false alarms associated with micro bubbles in the tubing. SMD Sensors can work with you to characterize your pump and tubing system to better separate false alarms from dangerous occlusion events.
Are you ready to build a medical device that’s advanced and delivers hospitals and medical professionals the accuracy and peace of mind they need in their workplace?
Don’t leave patients or the business at risk when sensors offer a solution.
Schedule a call or fill out our online form. A member of our team will be in touch to discuss your challenges and design ideas.
Strain Measurement Devices is known for our state of the art Load Cell technology, but our engineers have been designing an ever expanding sensor portfolio that monitors, measures and controls fluid. Fluid management sensors are a diverse collection across all of Strain Measurement Devices’ product lines. Customers are asking for sensors that can monitor fluid systems”noninvasively” (without contacting the process fluid). SMD has developed non-invasive fluid monitoring sensors to measure flow rate, totalized flow volume, bubbles-in-liquid, occlusions (blockage) in fluid flow tubing, internal tubing liquid pressure, liquid level in bags and vessels, and weight or weight change over time for flow rate.
Ultrasonic Fluid Technology
Fluid management and control sensors offer a variety of options in what and how your application is monitored. Many SMD product lines featuring ultrasonic technology, measurements can be done through non-invasive means protecting the integrity of any critical fluid. Ultrasonic fluid sensors operate by emitting pulses of ultrasonic sound (sound inaudible to humans) between two crystals. By monitoring these signals and applying custom algorithms, SMD ultrasonic sensors can monitor flowrate, totalized flow volume, bubbles, and liquid level. Since ultrasonic sensors do no need to touch the liquid they are ideal for difficult or corrosive fluids, such as acids, waste water, and others.
Ultrasonic Flow Meters technology exhibits superior time resolution designed for flow measurement in tubes. SMD clamp-on flow sensors measure flow rates with exceptional accuracy and turn down ratios. Paired with the touch screen electronic FlowDAQ system. Disposable ultrasonic In-Line flow sensors are also available for smaller tubing (< 1/4″ OD). The disposable in line sensor is ideal for applications requiring tight accuracy at flow rates. Another flow meter sensor offered is the ultrasonic In-Line Flow Meter sensor.
Bubble Sensors use proprietary digital noninvasive ultrasonic bubble sensing technology. The air-in-line detector allows for precise bubble size calibration for a range of fluids, allowing extremely accurate bubble detection. Air in line can be detected as small as one micro-liter in a wide variety of fluids and tubing. Using a proprietary control board integrated inside the sensor housing, we monitor signal strength until the bubble disrupts the signal. With a rapid sampling rate of 4000 Hz, SMD bubble sensors can reliably detect even the smallest bubble traveling at a high rate of speed. Custom characteristics can be provided for OEM users, many factors can be customized for your specific application needs.
Ultrasonic Level Sensors are ideal for applications where continuous level measurement is required. Time of flight of the sound signal is measured between the sensor and air-liquid interface. Alternatively, point level sensor float switches are adept at measuring when liquid levels are above or below a certain point. Horizontal, Vertical, Multi-level switches and fully customizable liquid level sensors are available. A full Liquid Level sensor guide is accessible on our sister site:fluidswith.com
Force/Pressure Sensors and Fluid
Pressure and Occlusions sensors offer many benefits to fluid management systems. Occlusion sensors can be used to detect pressure build up in tubing, indicating the flow in the tube is blocked. At SMD Sensors our engineers are able to combine standard ultrasonic fluid technology with our thin film, miniature occlusion sensors. Combined small housing options allow for multiple sensors in a compact unit: Combined Bubble and Occlusion housing unit.
Scales are used in a number of ways when it comes to fluid management applications. Examples include our IV Bag hanging scale which features an S251 Load Cell to weigh IV bags for accurate liquid levels. Also reagent waste bags being placed in our low platform, overload proof scales to keep contamination at a minimum. Mass weight over time to determine fluid flow rate is another application where fluid can be monitored and measured by low platform scales.
Fluid rate measurement can be done a number of ways. The method used typically depends on the fluid material that needs to be monitored. Measuring flow in tubes can be done through the use of various flow meter types including, paddle wheels, ultrasonic flow meters and vortex flow meters. However, most flow meter manufacturers actually use weight scales to calibrate their flowmeters.
For flow rate measurements of liquid using a scale, the fluid is placed into a container and on the platform of one of our many low profile precision weight scales. The weight is taken at the start of the procedure and ensuing weight measurements are taken at frequent intervals. The change in weight is divided by the amount of time it takes to calculate the rate of flow.
This solution is accurate, straight forward and generally inexpensive. The precision scale never comes into contact with the liquid keeping high sterilization procedures. The scale platform can be made in any number of materials.
Precision weight scales are a simple yet elegant product-line here at SMD, equipped with a full Wheatstone bridge through the use of our thin-film strain gauge technology. The low profile scales are calibrated with custom electronics with tight accuracy including non-linearity, non-repeatability, and percentage-per-year drift. Rugged construction is augmented by features such as splash resistance, RF immunity, overload protection, and unlimited color and material selection. Weight tray designs can be customized to fit a range of container shapes and include features like bottle stabilizing clips to secure the vessel in place.
Strain Measurement Devices has been hard at work engineering and designing new disposable sensors for each product line, offering contamination free and inexpensive sensors to help you with the monitoring in your application. One of these new sensors is the Capacitance Liquid Level sensor that detects fluids in all non-metallic containers, through the use of ultrasonic technology.
The Capacitance Level Sensor detects the level of a liquid inside the vessel from its non invasive mount, outside the container. The capacitance level sensor come equipped with an easy peel-and-stick attachment allowing users to attach this low-cost sensor to the outside of bags, plastic containers, glass bottles and ceramic vessels (non-metallic containers).
A unique power-on calibration feature allows users to attach the sensor to any non-conductive vessel for accurate detection of internal fluid volume. Because the sensor remains outside the vessel as to not contaminate any important fluid, perfect for sterilized applications where fluid needs to be closely monitored. The permanent fixture of the sensor is the box in-which alerts the user that the sensor is, on and detecting liquid level in the container.
Microfluidics is the focus of precisely controlling the behavior and exploitation of fluids that are physically constricted to a small scale. The liquid has the ability to flow in narrow spaces without the assistance of any external forces and because it’s on a micro-scale only low volumes are required, making Microfluidic devices ideal for lost cost applications.
One of the many benefits in measuring fluids on a micro level is that numerous operations can be completed simultaneously due to the compact size, ultimately shortening lead time. Another benefit, lowers the risk of human error through the micro fluid’s capacity to process and analyze fluid with the need of little handing.
SMD supports Microfluidics through a our ultrasonic technology featured in the Bubble Detector line. Our A130 bubble sensor is designed to detect bubbles or the presence of liquid in tubes with 1/16″ outside diameter. Also the detector has been tested with tubing as small as 0.02″ (0.5mm) inside diameter, allowing us to detect bubbles as small as 200 nanoliters. Standard bubble sensor design requires compressing the tubing by as much as 20% of the outside diameter, which is not feasible with extremely small tubes.
Our A130 bubble sensor uses a low durometer thermoplastic elastomer (TPE) over-molded onto a rigid ABS housing to achieve good acoustic coupling with these small flow channels. Both of these devices are currently used by many medical device manufacturers for critical fluid management applications. Microfluidic devices are incorporated with automation allowing the user to generate multi-step functions without the need for a high level of expertise all while featuring a number of capabilities. Therefore monitoring fluid with an SMD sensor, on a micro level has a whole host of benefits for accurate and repeatable OEM applications.
Optical Switch Sensors Successfully Operate Using Snell’s Law
Snell’s Law is used to predict how a light beam will refract or change it’s direction when traveling from one substance to another. θ represents (left figure) the angle between the direction of the light beam and a normal line (defined as the line perpendicular to the two surfaces at the point where the light ray passes from one substance to another. When light moves from a medium of a refractive index into a second medium with refractive index, both reflection and refraction of the light may occur.
Optical switches work by sensing the difference in the refraction index between various mediums, causing different degrees of refraction. When the liquid is not in contact with the sensor, all transmitted light is reflected back to the receiver. When the sensor is immersed in liquid, the light disperses throughout and less is returned to the transistor. The amount of returned light to the transistor affects output levels, making point level sensing possible.
Ultrasonic Optical Liquid Level Sensor
Strain Measurement Devices’ optical liquid level sensors consist of two main parts: an infrared LED coupled with a light transistor, and a transparent prism tip. The LED projects an infrared light outward; when the sensor tip is surrounded by air the light reacts by bouncing back within the tip before returning to the transistor. The main advantages of optical level sensors are their compact size, their lack of moving parts, and their low cost.
However, while extremely accurate for point level detection in high-stress environments, they’re less useful for continuous level measurement. In addition, optical level sensors are unsuited for applications where top mounting is necessary; when top-mounted, the accuracy optical level sensors may be adversely affected by moisture condensation.
Specialty combination sensors are a specialty at SMD Sensors, we have the ability to provide multiple sensors that work together in one application, and also have the ability to combine certain sensors together in small housing options to meet many detection needs in strict space requirements. The video below is a demonstration module created by engineers to highlight just some of the technology Strain Measurement offers and how our sensors can work seamlessly together.
Float Switches and Liquid Level sensors are used to determine the level of liquid present/absent in a container. Accurate, reliable, and often low costing, SMD Fluid Switch has a variety of sensors that can help your application to successfully run. In addition to measuring liquids, a float switch can control a pump, activate an alarm and even be used to control another electrical device.
Monitor rising liquid levels when a pump is activated (switches it on) when a threshold is met. Once the level is no longer determined by the switch, the pump will turn off again and continue monitoring for the next occurrence, this technique is used for things like flooding in homes/businesses. Engineers opt for the devices not only because they can be mounted in different ways and made of materials for use in different environments, but also because they are durable and can do the intended job for a great number of cycles with little need for maintenance.
Factors to consider when choosing a Liquid Level sensor
For the most accurate liquid level measurements determining the fluid used in the application is a key factor because different fluids have different characteristics. For example oil and grease are high viscous and require a different sensor than say a sticky or corrosive material. Even specific liquid gravity plays a roll in the choice of sensor. The layout of the liquid containing vessel is also important, thinking of mounting and the temperature, pressure requirements, and even elements like vibration. All these considerations help to achieve the most accurate measurements possible.
Conditional factors are a key consideration like would your sensor be submersed in the fluid, would you like to continuously monitor the liquid level or would you like to switch on and off monitoring. Thankfully our sister company, Fluid Switch has an extensive selection of standard fluid switches in multiple materials to help assist in application needs, more importantly being an OEM, they have the ability to create custom sensors that fit any unique requirements.
Critical Fluid Management in medical applications requires precise, repeatable, and reliable measurements. Strain Measurement Devices is a leading sensor manufacturer covering a vast array of measurement systems. There’s an important need for sensors that alert any critical interruption in infusion, insulin, enteral feed pumps, or wound irrigation systems. An occlusion sensor with thin-film precision is ideal, used to avoid any disastrous consequences by notifying the operator of anything wrong, like a pinched tube or pump failure.
Engineers utilize tube sensors to monitor pressure in pump systems that measure the force exerted onto a sensor pressed against any expanding walls of a polyurethane or PVC tubing. Sensors can also be placed behind the pump to record pressures as the pump backs up against the sensor during operation. Thin-film sensors have the ability to survive harsh environments and feature the accuracy required to be successful in critical applications.
For over 20 years Strain Measurement Devices has been using the state-of-the-art thin film vacuum deposition process to bond strain gauges directly to a number of materials. Thin film sensors are built without organic materials so that they are not hydrophilic, aged and fully oxidized. Over time, the thin film strain gauge has proven itself to be the preferred means for measuring strain in critical applications where small size, robust performance, long-term stability, and superior accuracy are required.
SMD Sensors Application SolutionsNoninvasive Tube Pressure Sensor for Occlusion Detection
A miniature force sensor can be used, mounted into a housing component and closed into a tube. The load-button of the sensor presses against the tube wall and when any expansion is detected in the tube, the sensor measures pressure changes. Strain Measurement Devices has developed a test that characterizes a tube sample so that the most appropriate force sensor range and the optimum pre-compression can be applied to the tube. Accuracy achievable by this technique is approximately +/-15% across a range of different tube materials or +/-5% for a single tube material.
Silicone tubing gives the best results from this approach, as it has low creep over time, but techniques can also be applied to deal with situations where the chosen tube material shows a stronger tendency to creep.
Precision Non-Invasive Pressure Sensor for Flow Measurement Application
This approach is for when a higher degree of accuracy is required, more than what can be obtained by a sensor directly applied to a tube wall. A disposable set with a molded membrane is an ideal solution, the sensor contacts the membrane via a flat plate. The sensor acts as a pressure-summing element. Due to the small full range deflection of the sensor, movement of the membrane is minimized, resulting in good linearity characteristics. In this particular case, the full range of the sensor is 1000 mbar, with an accuracy of +/-1 mbar. The example illustrated has a 0.5” diameter load surface.
This module was custom built by engineers at Strain Measurement Devices for multiple reasons: to highlight a number of different sensors offered by the company, to feature the way sensors can be easily custom built into housing units with multiple sensor and application functions, as well as showcasing how each sensor works independently and as a part of a unit.
The Air-In-Line Detector is used in this unit with with a siphon pump that moves the liquid from one chamber to another, when the liquid is removed from chamber one, the detector signals there is air in the line and switches the pump to chamber two. Next is the combination Bubble and Occlusion sensor that detects air in line and any pressure build up in the tube, like pinching or a blockage in the line, if either event occurs the pump shuts off completely and has to be manually restarted. This unit comes equip with a dial to introduce bubbles into the line and a clamp to cause a blockage in the line to demonstrate how the sensor reacts. The final demo sensor is an optical liquid level sensor that uses ultrasonic technology to sense the level of water, signalling the need to switch the pump from one chamber pump to another.
Strain Measurement Devices offers a vast portfolio of standard and custom made sensors for applications across almost every market. With six growing product lines we are able to solve many needs, in special housing and packaging that works best for your needs. To view any custom sensors, like the combination Bubble/Occlusion sensor please click here, from critical fluid management measurements to force sensor measurements.
The development of SMD’s proprietary thin-film process technology has yielded economic and performance benefits, enabling the company to considerably expand its served applications to include medical, industrial, automotive, and process control applications. Strain Measurement Devices’ thin-film sensors have significant advantages over silicon, foil strain gauge, capacitance, and other sensing technologies, at competitive prices.
Many advantages to thin film deposition:
One of the major benefits is the true molecular bond between the fixture (transducer) and the deposited strain sensing films. This flexure/dielectric interface is devoid of organic materials and oxygen which could absorb moisture or react in time. Sputtered thin film strain gauges are immune to the problems of organic backing materials found in bonded foil strain gauges. The lack of organics also means that elevated temperature operations to 250°C is within reach of these devices.
Thin film strain gauges are directly deposited onto sensing fixtures (e.g., pressure transducer diaphragms or load cells) in a vacuum deposition chamber by sputtering. The sputtering system also provides process control so that films may be deposited with good batch-to-batch repeat-ability. Significantly tighter control of bridge resistance and zero balance are routinely achieved in production than are possible with conventional strain gauges.
Long-term stability on thin film pressure transducers have been measured at better than 0.02% of full range output in an accelerated six-year lift test. Film deposition rate is approximately linear with input power and the rate may be slowed sufficiently so that very thin films can be deposited by integrating low powers over short periods of time. By modifying the sputtering parameters, strain gauge bridges can be fabricated which meet demanding insulation resistance specifications such as CENELEC (500Vac).
has been used for many years for the production of ultra-stable precision resistors is the strain gauge technology of the future. Some of the more interesting applications of the thin film sensor technology is within the medical field. When delivery of fluids to the body via infusion pumps, insulin pumps, internal feed pumps, and wound irrigation systems is interrupted by a pinched tube or pump failure there may be disastrous consequences.
Engineers often use what they call ‘tube sensors’ to monitor pressure in these pump systems by measuring the force exerted onto a sensor pressed against the expanding walls of a polyurethane or PVC tubing or they place the sensor behind the pump to record pressures as the pump backs up against the sensor during operation. Thin film sensors have the repeat-ability, ability to survive the rough handling and accuracy required to be successful in these pump applications.