Basic Pressure Sensors

When considering a basic pressure sensor for your application, you have to choose between a sensor compensated with some kind of electronics and a raw sensor without any electronics. Both types are quite different as far as pricing, function it fulfills and performance and it's worth to drop a few lines of explanations and give our customers some guidelines.

Non-Compensated Pressure Sensors

A non-compensated pressure sensor is a sensor without any electronics (electronics is usually used to compensate the pressure sensor). Senzors does not use any internal on-chip diode, any internal laser-trimmed resistors to create a first stage of compensation. Our full compensation is realized externally on a PCB. So a non-compensated sensor is just 4 resistors diffused in an encapsulated silicon chip and forming a Wheatstone bridge. See our technology section for more details. Below are the main features of a non-compensated pressure sensor:

• At 25°C (77°F), from one sensor to the other, electrical zero will vary from -50mV to +50mV

• At 25°C (77°F), from one sensor to the other, full scale signal will vary about 30% from a medium value

• Signal will shift quite dramatically with temperature

Needless to say that such a sensor cannot be used as is and needs to be compensated to at least read 0 for zero pressure and a standard, common value for full scale pressure. This is a minimum for most applications and could be sufficient for applications with narrow operating temperature range.

When to use a non-compensated sensor

A non-compensated pressure sensor is usually associated with a digital electronic. In this case, the sensor is digitally calibrated with a microcontroller. The microcontroller will characterize the sensor and will store its parameters (also called coefficients). During operation, these coefficients will then be retrieved by the microcontroller to calculate the pressure very accurately based on the sensor's output signal.

Digital compensation usually gives much better results than analog compensation. And when a sensor is digitally compensated by customer, it is not very cost effective to require a compensated sensor, which is more expensive, when a non-compensated sensor will work as good. Note that in this case, Senzors can characterize the sensor for you and give you the coefficients to enter in your microcontroller. Our specialized equipment and long experience almost always give better characterization results than customers' own characterization.

Compensated Pressure Sensors

A compensated pressure sensor is a sensor that integrates some kind of electronics to compensate the raw pressure sensor. So a compensated pressure sensor is a non-compensated pressure sensor to which a PCB has been added and with which the sensor has been calibrated under various pressures and temperatures. Senzors has many different types of electronics which can be associated with each sensor. These electronics can be as simple as a few compensation resistors on a PCB but can also integrate voltage regulators, amplifiers or microcontrollers to fit any application. Below are the main features of a compensated pressure sensor:

• Whatever the temperature within the compensated temperature range, the electrical zero will be set to a given value (usually 0 mV) and will have a minimal temperature shift

• Whatever the temperature within the compensated temperature range, the full scale signal will be set to a given value (usually a few hundreds of mV) and will have a minimal temperature shift

• There's no variation from a sensor to another. For instance, the output signal will be 0-100mV for all sensors. And basically, one sensor can be replaced by another without any adjustment.

When to use a compensated sensor

A compensated pressure sensor is usually associated with customer's analog circuitry or acquisition systems. It is very practical as one sensor can be removed and replaced by another sensor without having to recalibrate the sensor with the electronic. It is used where accuracy is not as critical since digital systems provide a much better accuracy, usually about 10 times better.