Equipment and Materials ♦ news digest pressure sensors.
The units included in the device are a configurable signal conditioner, a fast analogue/digital converter, configurable current sources, temperature drift compensation, digital sensor configuration, an SPI µC interface, adjustable linearisation, and a ratiometric, differential analogue output.
All of these functions are housed on a monolithic chip in a QFN32 package measuring 5 mm x 5 mm.
Mini CORI-FLOW M15 instrument
The firm says its miniature Coriolis sensor features superior response time and high accuracy, irrespective of changing operating conditions with regard to pressure, temperature, density, conductivity and viscosity.
The effective turndown is no less than 1500:1, with easy, on-site possibility for the user to re-range the instrument to his requirements, thus guaranteeing highest process flexibility.
The instruments have a robust IP65 weatherproof housing and are designed to withstand an operating pressure of up to 100 bar. Mini CORI-FLOW offers integrated PID control and close-coupled control valves or pumps, thus constituting very compact Coriolis mass flow control loops.
The Mini CORI-FLOW features digital technology, offering standard analogue and RS232 communication, optional fieldbus interfaces and additional functions such as alarms, totaliser (to measure fluid consumption) and batch dosing. The instruments feature fluid temperature and density as secondary digital outputs.
Multifunctional sensor interface monitor
The new iC-HO controller monitors the flow, gas, pressure and sensor temperature using an energised heating resistor
The latest iC-HO device is a universal sensor interface for the assembly of flow, gas, and
Resistive mass airflow sensors are driven by iC-HO using two identical reference currents so that the voltage difference conditioned by the programmable amplifier (PGA) can be measured and processed in a digitised form. A temperature control unit is also integrated into the chip.
With gas sensors, a variable tracking controller for two temperatures with a configurable temporal sequence is used. Differential, synchronous recording of the sensor resistance can be configured.
The company says with this controller, splitting the heating resistor and sensor resistor on a sensor MEMS element as iC-HO electrically separates the heating and measurement units.
With pressure sensors, for example, iC-HO provides differential measurement on a resistor measuring bridge as a half or full bridge. By performing an additional measurement the sensor temperature curve can be suitably compensated for.
It is also possible to supply the measuring bridge using a constant current source in place of a voltage.
For flow and gas sensor applications a heating system with a control circuit is also required in addition to the sensor conditioning unit. An on-chip heating controller drives a sensor heating resistor through additional differential sensor inputs and a digital PI controller with D/A conversion. The PI controller can exercise both relative and absolute control over the temperature. A maximum heating current can be specified to protect the external MEMS sensors.
Gain and offset correction of the programmable amplifier (PGA) can be automatically tracked for
January/February 2013
www.compoundsemiconductor.net 199
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