Sensors for Flow Meters

Very High Turn Down Ratios

Flow Meters

Flow meter solutions require high accuracy and outstanding Total Error Band performance.  Long-term drift specifications must be very good to ensure proper functioning over traditionally long industrial life cycles.  Additionally, high turndown ratios are often required in today’s advanced flow meter solutions. Achieving industry-leading, very high turndown ratios requires the use of a pressure sensor with an extremely low noise floor.  Superior Sensor Technology’s NimbleSense™ architecture has delivered products with the industry’s lowest noise floor specifications.

A mass flow controller is a device used to measure and control the flow of liquids and gases. Typical flow controllers have an inlet port, an outlet port, a mass flow sensor, and a proportional control valve. These are closed-loop control systems that adjust the output flow rate based on the value of a given input signal.  Mass Flow Controllers are designed and calibrated to control a specific type of liquid or gas at a particular range of flow rates. These controllers can be either digital or analog, with digital controllers typically able to control more than one type of fluid/gas as the calibration settings are programmable in nature.

Lowest Noise Floor

Superior Sensor Technology has optimized our NimbleSense™ architecture for Flow Meter applications with customized product variants. These products address the unique performance requirements of this market with a highly differentiated offering:

  • The lowest noise floor available to support very high turndown ratios
  • Industry’s best performance – Accuracy & Total Error Band
  • Increased stability with excellent long-term drift
Flow Meter Product Matrix

Differential Pressure Sensors for Flow Meters

Digital Flow Meter sketch

Advanced capabilities made possible with Superior’s NimbleSense™ architecture optimized for flow meters:

  • The lowest noise floor available to support very high turndown ratios
  • Industry’s best performance – Accuracy & Total Error Band
  • Increased stability with excellent long-term drift

We offer full customization of pressure ranges, number of pressures supported, bandwidth, update rate, output, etc.

Contact us to discuss your flow meter project

Recommended NimbleSense Features for Flow Meters

One device can support up to 8 different pressure ranges, and each pressure range is factory calibrated and optimized ensuring no degradation in total error band, accuracy or stability regardless of the range selected. This eliminates the complexity and headaches of working with multiple sensors.

Instead of having to research, purchase and design-in multiple parts, a single Multi-Range part simplifies both the design and manufacturing of a product. Designing in the same part throughout your designs is much more efficient than having to select multiple components. When you design in each of the Superior pressure sensors, the setting of the pressure is done via a single software command. It’s that simple. Add the fact that there is only one product to inventory, and your manufacturing team will also appreciate the value of Multi-Range!

Multi Range Comparison

Benefits of Multi-Range Technology include:

  1. Design flexibility with ability to ‘tweak’ pressure range throughout development cycle
  2. Simplified product design with one sensor replacing up to 8 different sensors
  3. Ability to quickly develop product variants at different pressure ranges without changing hardware design
  4. Greater economies of scale by purchasing larger quantities of the same product
  5. Reduced manufacturing complexity and costs due to simplified calibration of sensors
  6. Up to 8x reduction in sensor inventory costs and product obsolescence
  7. Allows manufacturers to build fewer product variants, significantly lowering working capital requirements and inventory

Closed Loop Control adds capabilities to set and maintain flow rates via pressure management by directly controlling motors, valves and actuators. Superior offers the option to have this capability integrated into the sensor in order to more effectively set and maintain flow rates by directly controlling motors, valves and actuators to maintain flow rate targets.

Basic Control Loop System

The integrated Closed Loop Control design significantly reduces loop delays in the electronic circuit by up to 100x. This integrated solution also eliminates the need to design and implement a complex control loop system, resulting in more efficient, more reliable and less costly products. Closed Loop Control is of extreme value in medical respiratory devices such as ventilators and CPAP, as well as in air quality measurement products.

The figure below shows a block diagram of an implementation of the Superior Closed Loop Control for an air quality application. In order to effectively measure the air quality, we require maintaining a constant/known airflow through the viewing window. The differential pressure across the venturi directly measures the flow into this viewing window. The system sets a target pressure level across the venturi and the differential pressure sensor automatically increases or decreases the drive to the pump to maintain the targeted differential pressure, ensuring a constant airflow into the viewing window. This is accomplished with the NimbleSense closed loop circuit used in combination with the company’s proprietary noise filtering, resulting in greater than 100x reduction in loop delay.

Clc Flow

Benefits of the integrated Closed Loop Control include:

  1. Greatly reduce loop delays to improve accuracy and responsiveness of your product
  2. Improve the reliability of your product by eliminating discrete parts
  3. Reduce your overall system costs
  4. Minimize system power and heat
  5. Simplify your product design
  6. Speed your time to market

Superior’s advanced digital filter is a multi-order filter that utilizes advanced filtering capabilities on the front-end of the sub-system to eliminate critical noise created by fans, blowers or other dry air/gas sources prior to reaching the pressure sensing sub-system. The NimbleSense advanced filtering capability removes sensor induced mechanical noise before it becomes an error signal that can adversely impact overall system performance. In customer deployments where our sensor replaced a competing component, we have seen greater than 10x reduction in sensor induced noise, thus greatly improving the SNR of the sensor output. In very low pressure systems, the improvement is even more significant.

Incorporating both standard and optional digital filters, this feature provides significantly better noise reduction and eliminates the need to design an external filtering system, resulting in more efficient, more reliable and less costly products. Our advanced digital filtering is optimized for each application to ensure mixed sampling noise is kept well below the noise floor. By removing the mechanical noise, we maximize overall system performance.

The example below is of a 4th order FIR filter customized to block pump noise above 50 Hz, which has noise of equal magnitude as the signal of interest. The lower graphs show the resulting impact of the advanced digital filtering.

Updated Adf Transfer
Updated Adf

Benefits of the advanced digital filtering technology include:

  1. Greatly reduced system noise levels by 10x or more, especially important in very low pressure applications. For noise prone systems, an improvement of 100x to 1000x is not unreasonable.
  2. Eliminate noise sources such as fans and blowers before they reach the pressure sensing sub-system.
  3. Simplify product design with an integrated approach.
  4. Speed time to market by not having to design an external filtering system.

A pressure switch is a mechanical or electronic device that is activated when a certain pressure threshold or set point is reached. These failsafe response components instruct the system to perform an action if a certain pressure threshold is met.

Types of Pressure Switches

Fixed Pressure Switches

As their name implies, fixed pressure switches have pre-set, non-changeable pressure thresholds that are set by the pressure switch manufacturer. The device maker receives the pressure switch already configured and cannot change values. Examples where fixed pressure switches are common are certain types of medical devices, such as ventilators.

Variable Pressure Switches

With variable pressure switches, the threshold value can be set either by the device maker or dynamically in the field. If it is controlled by the device maker, when they build their product they select certain resistor pairs that control the voltage input that determines the threshold. Once they build the product, the threshold value cannot be changed.

In cases where the threshold can be set in the field, this is typically done via software or a mechanical knob/switch. In this scenario, the pressure switch is usually not implemented as a safety feature. A good example is with air filters – where depending on the system implementation, the threshold value needs to be adjusted to account for any head loss in the flow stream.

Superior’s pressure switch changes state depending on the measured pressure being above or below a certain threshold. This can be used as a fast response failsafe feature for overpressure conditions, and to provide other simplified on/off system feedback. However, unlike other more common pressure switches, the Superior Sensor pressure switch includes three modes for setting threshold pressure, one fixed and two variable:

  • Fixed mode: Superior Sensor Technology sets the threshold and provides the ‘ready for use’ configured sensor (with integrated pressure switch) to the device manufacturer.
  • Variable mode 1: The device manufacturer can configure and set the proper thresholds at the time of product manufacturing.
  • Variable mode 2: Pressure thresholds are field programmable via software, so the pressure switch can be ‘tuned’ after product manufacture depending on the use case.

Benefits of Superior’s integrated pressure switch include:

  1. Flexibility with 3 modes of operation
  2. Lower system cost as need for an external pressure switch is eliminated
  3. Smaller overall PCB footprint
  4. Improve the reliability of your product by eliminating external components
  5. Minimize system power and heat
  6. Simplify your product design
  7. Speed your time to market