This transducer is designed for a wide application in a branch of measurement and regulation in a range of very small pressures, especially in air-conditioning, ventilation, combustion process control, appliance design, etc. Many applications are offered in a medical technology and in the laboratory measurements. This transducer is designed for measurement of the differential pressure and this fact also includes a requirement for measurement of the relative pressures. However, it is not determined for a high common pressure measurement, such as measurement on the orifice gauges in the pressure distribution systems. The version for measurement of the absolute pressure, consequently the barometric pressure, is worthy of a special attention. Changes of the barometric pressure are essential for many industrial processes, some medical indications, possibly for the objective automated recording of the laboratory conditions, etc. For the purpose of these measurements, there are produced transducers with a specially modified range with suppressed zero. The medium being measured may be a non-aggressive gas.
The whole transducer, i.e. a pressure sensor, supply, compensation and amplifying circuits as well as a filter for increase of the noise immunity, are placed in a small plastic box from polycarbonate, which may be installed on a panel or DIN strip. The pressure supplies are realized by the nickel-plated brass inlets with a diameter 5 mm, which are suitable for use of a small hose, possibly a quick coupling for higher pressures. In addition, the medium comes into contact with silicon, silicone rubber and a plastic substance polyetherimide.
Electric connection into the measuring circuit is realized by a sealing arrested miniature connector type DIN 43650 - C with a cable outlet
PG7, which enables to use a cable with a diameter max. 6.5 mm.
This type of transducer measures the pressure by means of a silicon diaphragm on a piezoelectric principle. Therefore this transducer attains a good overload endurance, is resistant against vibrations and may work in an arbitrary position. It is an advantage for some applications to measure both the positive and negative pressure with one transducer. Electronic circuitry is realized by a surface mount technology.
Output information about the input pressure is transmitted by a current or voltage. This current signal is used in either two-wire 4–20 mA or three-wire 0–20 mA variant, the voltage signal is used in a variant with a range 0–10 V. There may be as well set up different values, namely the voltage outputs. The transducers may be supplied by a d.c. voltage in a range 12–36 V. Change of the supply voltage within this range has not any practical impact on the measurement accuracy. This transducer is calibrated permanently to the specified range. Fine adjustment (approx. by 2 %) of the end points of the transfer characteristic may be carried out by means of the trimming resistors, which are accessible after removal of the transducer cover. Trimming resistor for the zero setup is marked in red. Under the cover, there are placed short-circuiting jumpers for selection of the damping time constant. It may be as well agreed that all the transducers should be fitted with the 3.5-digit LCD display, which shows an up-to-date value in arbitrary units.
We recommend to use the standardized pressure ranges, but it is possible to agree adjustment of an arbitrary range within the specified pressures and outputs, including the symmetrical and asymmetrical combinations of the positive-negative pressures.
