Baratron Calibration

The accurate and precise measurement of pressure and vacuum is critical in many fabrication processes such as in the production of electronic, photovoltaic, and other semiconductor devices. Baratrons are devices that measure pressure and vacuum accurately.

 

Baratrons are analog, high-performance vacuum and pressure transducer manometers. They provide a high-level DC analog output signal that is linear with pressure. This analog output can be interfaced with a pressure controller or sent to a display.

 

Baratrons are capacitance-based devices and they detect the variations in the pressure by measuring the corresponding change in the capacitance between the sensor’s diaphragm and the attached electrode.

 

This capacitance change is converted to a useable output by signal-conditioning electronic circuits. The radially-tensioned diaphragm in the sensor provides a very fast response.of a few milli seconds. It has low hysteresis, excellent repeatability, very high resolution. These devices are exceptionally high corrosion resistant, as they have an all-around welded design. The sensor itself can withstand repeated exposures to variations in pressure without significant degradation of performance which allows it to operate with almost any process system.

 

Technology behind Baratrons

 

The Baratron which has an electro-mechanical design can measure both pressure and vacuum. The capacitance gauge detects and converts the movement of the diaphragm due to pressure changes into an electrical signal. This signal is directly proportional to the pressure. The pressure sensor is the thin diaphragm that is sensitive to the pressure or vacuum that is exposed to it through an inlet tube. An electrode, which typically is a ceramic disk with good conductivity is mounted behind this diaphragm.

 

Pressure differences between the process and the reference cavity push the diaphragm slightly which changes the distance with the electrode. This change of distance produces variations in the capacitance between the diaphragm and the electrode. This variation is translated into an electrical signal which is proportional to the pressure change. This electrical signal is now amplified by the electronic circuitry and is transmitted to the process controller or display.

 

The capacitance signal is generated by the physical changes within the device and not due to any changes in the gas properties, so the pressure measurements by the device are quite independent of the composition of the gas. In industrial processes, the chemistry of the gas can change quickly but even in such cases, the capacitance manometers give accurate results.

 

Types of Capacitance Sensors

 

There mainly two types of sensors:

  1. Absolute capacitance manometers in which the reference cavity is evacuated to high vacuum so that the pressure measurements will always be referenced to vacuum.
  2. Differential capacitance manometers. These devices do not have a reference cavity but they just have a tube that is connected to any vacuum or pressure source. These manometers read the difference in pressure between the inlet tube and the reference cavity at the backside of the electrode. They are commonly used as safety switches and for airflow pressure drop measurements.

 

Design and construction of sensors

 

The overall manometer sensor construction is critical for safety. These sensors are fully welded and are tested for leaks before final assembly. In the event of a failure of the diaphragm which is extremely rare, the process gases are completely contained within the sensor which does not allow them to escape in the environment. No other pressure or vacuum gauge offers this level of reliability and safety.

There are inherent simplicity and ruggedness in the design of these devices. Their wettable parts are made of stainless steel or ceramics making them quite reliable and long-lasting. The entire mechanical assembly and electronic circuitry are packaged in such a way that these transducers exhibit high performance and excellent reliability.

 

Calibration of Baratrons

 

Capacitance manometers typically read pressure or vacuum over a four-decade range. Like all precision electromechanical devices, capacitance manometers require exact calibration at the time of manufacture. They must be periodically recalibrated to maintain the specified accuracy and performance. The user should regularly recalibrate a capacitance manometer following the factory recommendations; otherwise, there is the possibility that the device will give wrongs results. This situation cannot be acceptable in a process environment as it may cause reduced productivity or even a complete shutdown of the process line.

Capacitance manometers are frequently used as reference devices for other types of gauges which means that they are the calibration standard against which other devices are measured.

Capacitive pressure transducers are now quite commonly used in both highly specialized and general process environment that requires accuracy, ruggedness, and stability. They are especially useful in difficult environmental and operating conditions such as high temperatures, shock, and vibration. These devices are inherently rugged, electrically simple, and economical, therefore are quite popular with design engineers.

 

e2b calibration is an ISO 17025: 2017 accredited facility. We can calibrate your Baratron transducers to the highest industry standards. Our services are unmatched in the industry Please contact e2b calibration for all issues related to Baratron calibration.

 

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