This blog post was submitted by David Grice a systems architect at ZMD America.
Designing and implementing sensor interface designs for nonlinear, temperature-dependent transducers presents some difficult challenges. The advent of dedicated and powerful Sensor Signal Conditioning (SSC) ICs has made the job easier, but choosing the right IC for a particular sensor and application is critical for making optimal performance and cost tradeoffs. In this article we will examine some of the most important features and functions to consider when choosing the best SSC for your application.
Knowing your Sensor
The first step in choosing an SSC is to understand the characteristics of the sensor that it interfaces. Sometimes a designer is tempted to skip this step and pick an SSC with the most powerful and complex correction techniques that are available or affordable. This is not only wasteful in terms of cost and loading on expensive production testing resources, but often detrimental. Depending on the intelligence designed into the correction algorithms, sometimes a higher-order equation fit will create more error than a simpler equation that more closely matches the inherent response of the sensor. Characterizing and analyzing sensor behavior over all environments is time well spent.
The Right Partner
Before plodding through pages and pages of datasheets to understand every tedious detail of dozens of potential SSC candidates, take a step back and evaluate what level of support and overall experience the manufacturer provides with their products. This is especially important for a product like an SSC where complex equations are used to calculate the correction coefficients. If the manufacturer does not provide development hardware and software to automate and evaluate the calibration routines, you will be left to develop those resources on your own. Even more important is the ability and willingness of the manufacturer to answer questions about their product and support materials that routinely arise during the development phase.
Total System Cost
Another commonly overlooked factor in SSC selection is the production cost of calibration, especially for high-volume applications. Sometimes a cheaper part will actually end up costing more overall because it uses an unsophisticated calibration routine that requires more time on costly testers and environmental chambers. The ZMDI family of SSC products is designed with this in mind. Their intelligent correction algorithms allow for “single pass” calibration that minimizes the time required for data collection and for coefficient calculation and programming. This is a tremendous benefit and should be given serious consideration in the selection process.
Narrowing the Field
After selecting the right partner and family of products, the choice must be narrowed to an individual part. Typically, the process of elimination is the easiest and fastest way to accomplish this. For example, the ZMDI SSC product family is broadly divided into resistive and capacitive bridge sensor types. If your sensor is capacitive, the candidates will be limited to the ZSC312X series.
After sensor type, the next criteria that narrow the range of products most quickly are the qualification level and environmental requirements. For automotive level quality (AEC-Q100), the available choices are the ZSC31150, ZSSC3170, or one of the ZSSC31xx products. Applications that do not require automotive qualification can use any of the ZSC310xx or ZSSC30xx parts.
Once the field has been narrowed to this point, the remaining criteria for completing the selection process are operational constraints such as gain and resolution, response time, supply voltage and current, and output interface type (analog, I2C, SPI, etc.). If multiple parts meet all these requirements, the final selection can be made based on price or special features like alarm outputs or sensor diagnostics.
Options + Process + Experience = Success!
Abundance of choice can be a double-edged sword, but a methodical approach combined with an experienced partner will make the selection process smooth, efficient, and successful.
Learn more about sensor signal conditioning
Servoflo is pleased to announce the addition of new LED drivers to the ZLED7x20 & ZLED7X30 families. Both groups are high current 40V LED drivers. The ZLED7X20 has an internal switch while the ZLED7X30 has a switch dimming function.
Both families require a low bill of materials and have a small footprint. Thermal shutdown protection and LED open circuit protection is included. Typical applications include:
- Interior/exterior LED lighting
- General purpose consumer LED applications
- MR16 LED spot lights
- Architectural lighting
- Retrofit LED lighting fixtures
This chart summarizes all LED Drivers available. It is a simple way to quickly evaluating the key features of different models. Evaluation kits are available for purchase.
To see all LED Drivers, visit our LED driver section of our web site.
You can also download our LED driver product & pricing guide!
Servoflo has posted a new paper written by Dr. Norbert Rauch, a well-respected sensor engineer in Germany. His paper, titled "The 24-bit Revolution in Pressure Sensor Technology", discusses how altitude can be accurately measured with the impressive resolution provided in the MS5607 silicon-based pressure sensor, which uses the latest 24-bit ADC technology.
Most traditional altimeter sensors have resolution of several meters, making them not very precise. These traditional sensors have a digital signal conditioning unit and operate on a 14-bit ADC. However, a 14-bit ADC does not automatically mean that the signal can be resolved with 14 bits. Depending on the signal span, offset, and the signal evaluation electronics, possibly 10-12 bits are available for signal conditioning. Until now, achieving a better level of resolution was only achievable with a complex pressure sensing system which is costly and difficult to achieve.
The paper discusses how the MS5607 eliminates these problems with the use of an ASIC and MEMS technology. By taking into consideration that resolution must not be confused with precision, calibration accuracy and offset drift due to temperature changes must also be considered when assessing solutions. Physical size and power consumption are also factors for designers.
The paper will educate readers on how to better understand the importance of the 24-bit designs and implications for applications.
The following is a new product announcement:
The new ZSSC3123 is a low power capacitive sensor signal conditioning IC that supports a broad range of sensor types and gives engineers a cost-effective component option for sensor designs.
With 14-bit resolution and 0.25% accuracy, the ZSSC3123 has first-pass calibration and low power consumption at 60uA with sleep mode lowering current consumption to <1uA. Target applications include low power battery driven sensor applications, sensors for humidity, weight scales, load and compression sensing, as well as tension control.
Capacitive sensors are often favored for their small size and lower power consumption. The ZSSC3123, complements these features and provides designers an optimal solution. The device is particularly suited for MEMS-based sensor elements, such as pressure sensors for hydraulic control systems, humidity sensors, and liquid level gauges. The ZSSC3123 connects to microcontrollers but can also be utilized in stand-alone designs for transducer and switch applications.
The ZSSC3123 can be configured to interface with capacitive sensors from 0.5 to 260 pF, with sensitivity as low as 125 atto-Farads per digital bit. The part can be used in both single and differential input sensor configurations. The device offers full 14-bit resolution for compensation of sensor offset, sensitivity and temperature.
Accuracy at the standard supply voltage of 2.3 to 5.5V is 0.25% over the -20C to +85C range and 0.5% from -40C to +125C. I2C and SPI interfaces as well as PDM or alarm outputs are provided.
Pricing will be available shortly.
Servoflo has a SHORT 6 question survey about how you search for components.
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As Internet use continues to increase to search for components, we would like to learn more about how you find parts. What tools are useful to you - Google, Twitter, blogs, trade journal web sites?
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Recently an article was published in Design News about digital humidity sensors offered by Servoflo.
Typical problems of traditional integrated sensor solutions include poor accuracy, unstable behavior around the measuring range limits and unsatisfactory chemical resistance against contaminants. Additional limitations are lack of dew formation resistance, inadequate long-term stability and failure during load spikes.
This article provides technical details about how these problems are solved with new digital humidity sensor technology. In depth details about design features and manufacturing techniques are discussed. Topics include ASIC functionality and design, construction, and what this means for the functionality of the humidity sensor.
Anyone who is considering designing in a digital humidity element should take a quick look at this topic. Please feel free to post a comment or question.
Read the complete article here.
We have updated our medical applications area with the latest pressure sensor products. The goal of this section is to provide you with a quick and easy way to find sensors by application. Pressure sensors are becoming increasingly important in medical equipment. The latest technologies available give designers flexibility in how sensors are used. Lower tolerance sensors combined with sensor signal conditioning lets medical equipment designers choose more cost effective solutions while tailoring a sensor to their specific needs.
View your specific medical application here:
Blood pressure measurement
Deep vein thrombosis
Within each of these product areas are specific pressure sensors appropriate for that application. If you do not see a product that fits your needs, please feel free to contact us about your specific application requirements. We have access to additional pressure sensors and transducers that are not on our web site. Our extensive knowledge in the medical market gives you expert access to what are the most important sensor features needed.
If you have a story to share about your experience with pressure sensors in the medical market - problems, solutions, things to watch out for, please feel free to post them here.