Topics: Pressure Sensors
General anesthesia machines typically deliver a cocktail of gases to a patient to ensure sedation during surgery. Nitrous oxide (also known as laughing gas) and other gases are mixed with oxygen and delivered to the patient. The buffer area shown in the drawing below is where the combination of nitrous oxide and oxygen is mixed together. Here, the anesthesiologist needs to be aware of the mix of gases that is appropriate to the patient. At times, the combination needs to be adjusted depending on patient requirements.
To control the level of oxygen and nitrous oxide delivered to the buffering section of the anesthesia machine, it is necessary to measure the volume of each gas. In the drawing below, the FS4008 mass flow sensor is shown as a method to measure and monitor the various gas levels. The FS4008 comes in various flow ranges from 0-10 SLPM up to 0-50 SLPM. Available outputs include linear voltage or digital RS232 or RS485, allowing for the FS4008 to be easily integrated into a control system for the various gases. The flow channel diameter is 8 mm, and there are exchangeable mechanical connectors for ease of installation (BSPT thread and one-touch connectors).
At the delivery location of the gas mixture to the patient, another flow measurement point is needed. Here, the FS6022 mass flow sensor can play an important role in ensuring gases are delivered to the patient and then subsequently exhaled. Because the FS6022 has bi-directional measurement capability, it is ideal for use in the scavenging portion of the anesthesia machine, which expels the used gas from the patient's lungs. For details about the FS6022, you can also review our blog post: Mass Flow Sensors for Medical Ventilators.
In summary, measuring and monitoring mass flow of gases in anesthesia equipment is a critical part of patient comfort and surgery success. Not only is it important to measure the mix of anesthesia gases, it is also vital to measure delivery of the gases to the patient.
You can learn more about mass flow sensors here or download our mass flow product & pricing guide.
Topics: Mass Flow Sensors
Servoflo is pleased to announce the availability of new evaluation kits and a new driver board for the mp6 micropumps. The new Quad Series lets users drive up to 4 pumps simultaneously. This means that a user can design an electronics system using 1 mp6-QuadOEM to drive 4 mp6 pumps. Even more exciting, the new technology lets users increase the pumping rate of the mp6-air to up to 42 ml/min, since frequencies can be increased to 800 Hz as opposed to 300 Hz for the original mp6-oem. Pumping rates for liquids using the mp6 remains at 7 ml/min.
Here is a summary of the new items:
mp6-QuadEVA: This kit comes with the QuadEVA board, 4 pumps, mini USB cable. An air version (mp6-air-QuadEVA) is also available.
mp6-QuadKEY: This evaluation system has a detachable mp6-QuadOEM, and uses Arduino as an interface. An air version (mp6-air-QuadKEY) is also available.
mp6-QuadOEM: New controller can be used by itself for integration into production. Parameters can be changed via I2C.
To help understand the various performance differences between controllers, the 2 charts below describe the pumping performance for water and gas.
To fully understand the different options, we suggest you start by reviewing this tech note, Controller Overview.
Then, we also suggest reviewing the product manuals:
To get pricing on these evaluation kits, you can simply email us at firstname.lastname@example.org or you can download the Micropump Product & Pricing Guide.
Servoflo is pleased to announce the availability of a driver reference design for the mp6 micropump. Written by Microchip, the application note describes the implementation of a basic circuit for driving the mp6 with flow control for a fluid delivery system.
The application note includes a description for a control board, a high voltage driver board, and the mp6 micropump. The control board provides the adjustable voltage and frequency control signals to the high voltage driver board. Then, the high voltage driver board delivers the boosted signals in specific waveform on multiple output channels with adjustable peak-to-peak voltage (VPP) and frequency to the piezoelectric micropump. The demo can supply a maximum of 250V of VPP and a maximum frequency of 300 Hz. A bill of materials is included with the application note.
The mp6 micropump is designed to pump 0-7 ml/min of fluids and up to 18 ml/min of air/gas. Applications include medical devices, drug delivery, call
Metallux SA, based in Switzerland, not only offers ceramic pressure sensors but also thick film technology hybrid circuit design and manufacturing, i.e screen printing on ceramic, FR4, Flex, steel, aluminium nitride, sapphire, etc. Metallux SA also offers the capability to integrate electronic components such as IC's, resistors, capacitors, etc.
Why use a hybrid circuit?
- High temperature demands. Circuits can be designed to withstand more than 85°C or for harsh environmental conditions such has high humidity.
- Low & medium power requirements around 2-3 kW. Ceramic is a very good heat dissipator.
- When trimming is required. It is possible to trim the screen-printed resistor on circuits with electronical components to adjust a voltage, current or frequency output.
- A smaller size is needed
- Enhanced security. It is very difficult to reverse engineer a hybrid circuit.
- Need to use resistors and conductor tracks to create a power source (such as from millawatts to 3-3 Kilowatts)
- More resistant to shock & vibration
From design to screen printing to assembly, Metallux provides a complete hybrid circuit solution for their customers. Some examples of their capabilities include:
- Superior manufacturing area with 3 cleanrooms
- Multilayer hybrid circuits with integrated trimmed resistors (from mohms to Gohms)
- Active/passive SMT, from 0201 size to BGA and µBGA
- Chip & wire: die attach, wedge & ball bonding, encapsulation, on all kinds of substrates
- Flip-chip: solding & epoxy
- Finishing & encapsulation with conformal coatings, epoxy & silicone resins
As an example, here is a real world hybrid circuit design by Metallux:
Silicon pressure sensor for home boiler: A thick film hybrid circuit was designed for better stability in a harsh temperature and humidity environment. The stable and rigid substrate had the die pressure sensor glued onto it. The coefficient of thermal expansion (CTE) of the Alumina is lower compared to a standard PCB.
To discuss how hybrid circuit technology can help you, please contact us.
Topics: Ceramic Pressure Sensors
A ventilator uses pressure to blow air or a mix of air and oxygen to a patient. This blog post describes how the FS1015FL (shown on the left below) and FS6022 (shown on the right below) mass flow sensors are used in medical ventilators. These mass flow sensors are members of the new Siargo line which Servoflo is now offering.
Both of these mass flow sensors use a MEMs sensor chip based on the calorimetric principle. The chip is packaged in a special way to receive laminar flow. The sensor chip has a micro heater and a pair of sensors upstream and downstream. When gas flow passes over the sensor chip, it brings the heat from upstream to downstream. Mass flow rate is calculated by measuring the temperature differences from the upstream and downstream sensors.
The illustration below shows how the mass flow sensors are installed inside the ventilator. The inlet air and oxygen is mixed and delivered to the buffer and valve. The FS1015CL sensors are calibrated for either 0-100 SLM or 0-150 SLPM. The flow rate of air/oxygen is measured to ensure the correct amount is delivered to the patient. The FS1015 has a 5V supply with a linear voltage output or an I2C interface. Standard ISO 15 mm medical connection is available.
The FS6022 is a mass flow sensor with a bi-directional option. Ranges include up to 250 SLPM or 300 SLPM. Having a standard voltage output, the bi-directional model provides a 2.5 to 5V output for the positive full-scale flow rate and 2.5 to 0 V for the negative flow rate. Here, the FS6022 is used to monitor the inhalation and exhalation of the patient.
These sensors can be sterilized in medical liquids.
We have a recently updated mass flow sensor product & pricing guide which includes these models.
Topics: Mass Flow Sensors
Analog Microelectronics has an application note discussing how to monitor HVAC fan and filter performance using the AMS5105 pressure sensor. The AMS5105 is a board-mount, compensated and calibrated pressure sensor with an analog ratiometric 0.5 to 4.5V output along with two discrete, programmable logic switching ports. For each switching port, the switching function, threshold, hysteresis and delay can be set individually. Having low differential pressure calibration from 100 mbar down to 5 mbar, the AMS5105 is ideal for fan and filter monitoring systems.
Included with the application note are the following four application examples with circuit drawings :
- Simple HVAC Filter Monitoring System With Pre-Warning - Here the switching ports are programmed as normally-open and hysteresis is set to 5% of the calibrated pressure range.
- HVAC Filter Monitoring System with a 24V Supply and Robust Outputs - Similar to the first example but includes details what to do if only 24VDC is available as a supply.
- HVAC Filter and Fan Monitoring System With Diagnostics - Learn how to set up the switching ports for normal and filter replacement
- HVAC Monitoring System with Diagnostics Measured at an Orifice - Similar to #2 but measurement is taken across an orifice to protect the sensor from contaminants.
Here is the circuit drawing for item #1, Simple HVAC Filter Monitoring System With Pre-Warning:
As you can see, this application note gives great details on how to use the AMS5105 for HVAC filter monitoring. We hope you find it as a useful tool that can be applied across many different applications.
Topics: Pressure Sensors
Different methodologies exist for creating leak detection systems. In this blog post, we will focus on leak detection using a pressure decay method which is ideal for detecting very small leak rates.
The diagram below illustrates a classic leak detection setup using pressure decay.
The test part is pressurized from a pressure source. At the first X under "Balance" in the chart above, the pressure setpoint is reached and balance is maintained until the leak detection test begins at the second X. The regulator and valve isolate the test part from the source once pressurization is complete. The pressure sensor monitors and measures the pressurized test part. If the pressure measurement decreases, then air is leaking out of the test part. Measuring the change in pressure over a period of time allows the user to calculate the leak rate.
The availability of easy-to-use, sensitive pressure sensors at low cost lets designers optimize their leak detection design. The AP3/AG3 Series is an example of a pressure sensor well-suited for leak detection applications. The AP3/AG3 is a calibrated and temperature-compensated pressure sensor with ranges from 0-25 kPa up to 0-1000 kPa. Not only does this sensor have high accuracy of ±1.5% full-scale, the AP3/AG3 has built-in threshold detection (consider how easy it is to set the threshold for the start of the leak test). The AP version has a dual-in-line package while the AG version is surface-mount. With a price of of approximately $7 (depending on the model) at 1,000 pieces, the AP3/AG3 provides has an excellent price-performance ratio.
Applications for leak detection include:
- Medical devices such as drug delivery, catheters, valve, oxygen delivery
- HVAC including refridgerant testing, heat exchangers, tubing, radiators, and more
- Automotive testing such as emission systems, fuels, pumps, and cooling systems
- Various industrial applications
Topics: Pressure Sensors
An oxygen concentrator is a medical device to deliver oxygen to a patient. A typical concentrator consists of a compressor, absorption columns with air filters, circuitry, a product tank and regulator. Oxygen concentrators differ from machines delivering compressed oxygen from tanks filled at a separate location. Instead, an oxygen concentrator takes standard room air, filters out the nitrogen and other gases, leaving oxygen to be delivered to the patient.
The block diagram shows a design of a typical oxygen concentrator. Pressure and oxygen sensors are used at various points to ensure proper creation and delivery of oxygen. For example, a pressure sensor is used at the product tank to measure the tank's level and to ensure there is proper flow moving into the regulator.
Often times there is also a pressure sensor between the regulator and outlet oxygen. A stationary oxygen concentrator may use a pressure sensor in the 50 kPa range to detect a kink in the tubing. (See AP2/AG2 analog pressure sensor or AP3/AG3 pressure sensor with threshold detection). For portable oxygen concentrators, a pressure sensor in the 1 kPa range is used to detect inhalation which then controls the regulator. Here, it is important to use a pressure sensor that is sensitive enough to detect the low flow rate of breathing but can also withstand high overpressures. The AL4 is a good option meeting this requirement.
Finally, and perhaps most obviously, an oxygen sensor can be installed to sense the oxygen percentage of the air being delivered to the patient. The oxygen sensor allows the designer to create alarms and set points for the filtering portion of the concentrator.
The abundance of sensing technology has allows for the development of more flexible medical equipment with more features and functionality. This description of oxygen concentrators is one example of where the evolution of technology has created better health for all.
Oxygen measurement is critical in a wide range of applications. From ensuring enough oxygen exists for life sustainability and development, to monitoring harmful and dangerous gases, oxygen sensing can be found in medical equipment, HVAC systems, industrial processing, instrumentation, and the new exciting field of additive layer manufacturing with metals and alloys.
The oxygen sensors offered by Servoflo are a zirconium-based sensor. The sensing element is heated to more than 350°C which allows oxygen molecules to penetrate the sensing chamber. A voltage is applied to pump the oxygen out of the chamber. The measurement current produced is proportional to the quantity of oxygen molecules pumped away.
Key advantages of the zirconium-based approach include:
- Long-term stability with minimal drift
- The operating lifetime of the sensor is greater than 4 years
- Temperature operation up to 300°C
- Ambient pressure has no effect on oxygen measurement, eliminating the need for pressure compensation
Stand-alone oxygen sensors with a raw signal output are available. Users have to take the sensor signal and provide compensation and amplification. Alternatively, Servoflo is offering signal conditioned sensor modules with either an analog or digital signal output, the FXC-MLxx or FCX-MCxx Series.
The FXC-ML or FXC-MC has the following features:
- Can be configured for flow (force air into the sensor) or diffusion operation (sitting open-ended)
- Configurable for analog output or digital output
- Sensor head and connecting cable can be configured for 200°C
- Measurement ranges include 0.1-25% and 0.2-95% O2
- Accuracy of ±0.5% FS
- High quality Swiss manufacturing
- Standard off the shelf modules can be easily customized to meet your specific requirements
|0.1 to 25% O2||0.1 to 25% or .2 to 95% O2|
|24VDC supply||24VDC Supply|
|4-20 mA output (logarithmic)||Linear analog of 0-10V, 0-20 mA, 4-20 mA included. Digital outputs available.|
|Learn more about FXC-MLxx||Learn more about the FCX-MCxx|
A wonderful aspect of these products is the ability for customization of many features. Here are some examples of customized versions of the FCX-ML/MC oxygen sensor modules:
CO2 incubators/cell culturing: The customer required I2C only for an output, and a sensor head to withstand 200°C while the cable and sensor head connector needed to withstand 180°C.
Critical containment and ventilated small animal enclosures: A customer required an RS485 output with DIN41612 for rack mounting.
Additive layer manufacturing with metals and alloys: 3D printing with metals and alloys is a new, growing field. The quality of the finished part is directly proportional to the oxygen concentration (the lower the better, ideally >1%). Special cable terminations were provided to prevent EMC issues.
Additional examples of customization are shown in the image below.
Should I use the oxygen sensor element only or buy a packaged solution? The answer is, it depends. A packaged solution such as the FCX-ML or MC is great for users who need to find a quick solution to evaluate the oxygen sensor without having to create electronics and circuitry. If a user has in-house expertise to compensate the raw signal, provide the electronics and desired packaging, then purchasing the sensor alone is a viable option. The packaged solution is great for those with limited resources to develop electronics and need help with packaging and design. Here, you can let Servoflo solve your sensor integration issues for you.
Topics: Oxygen Sensors