Differential Pressure & Flow Transducers

PCI's transducer family

This brochure describes instruments that are "standalone" components of a complete control system. This is, they are mounted in their own separate enclosure and are usually wall-mounted. The same instruments can be combined into one enclosure which would be the control panel for an entire system or major subsystem. The four families of instruments covered herein are Series DPT Differential Pressure Transducers, Series IT Flow Transducers, Series FI Flow Indicators, and output signal conditioning modules.

Series DPT Differential Pressure Transducers
DPT Transducers measure pneumatic input differential pressure and converts that signal to a electronic analog output signal that is sent to a controller or indicating device. These transducers require a 24 VAC/VDC power input. DC output signal is carried on a twisted pair of wires.

Series FT Flow Transducers
FT Transducers are similar to the DPT Series except that both total and static pressure inputs are required. The difference between the two pressures is velocity pressure that is converted by the transducer to velocity (fpm) or with the duct area known, to airflow (cfm). The output is an electronic analog signal for use by a controller or indicator.

Features of each model are identified and described below.

PCI's Variable Capacitance Pressure Transducers
are simple and very reliable sensors designed for high accuracy measurement of low differential pressures. A lightweight, ultra-responsive stainless steel diaphragm and an insulated electrode form the variable capacitor. A unique electronic circuit detects the change in capacitance and produces a 4 to 20 mA or 0 to 10 VDC current output signal linear to the measured differential pressure. The high level output signal, the excellent long term stability and the fast dynamic response of the PCI transducer makes it ideal for a wide range of commercial, industrial, laboratory and aerospace applications.

The Automatic Zeroing Circuit
performs a zero calibration of the differential pressure transducer output at user-selected intervals. Uninterrupted control and/or indication is maintained at the last output value during the approximate two second calibration period. The transducer resumes its real-time analog output response after zero calibration is complete.

The Signal Scaling Circuit
converts the differential pressure signal (static pressure, or velocity pressure converted to velocity in fpm or airflow in cfm) to a user-specified full scale value.

The Digital Display
shows the converted transducer output signal on a 0.5" high four-digit light-emitting diode (LED) which is door mounted for local monitoring capability.

The Square Root Extractor Circuit
is used in all flow transducers to conform the output to the square root curve of velocity vs. velocity pressure. This circuit is essential for signal accuracy when the output is made linear to velocity or airflow.

The Analog Meter
is a diaphragmactuated differential pressure gage directly connected through bulkhead fittings and tubing to the static pressure or airflow measuring element.

This provides a continuous and direct indication of the true measured value independent of the hydraulics or electronics of other control components, and thus provides an instant visual check on the system status. The meter is provided with either a dual scale (fpm and cfm) for airflow readings or a single scale in inches of water for pressure readings. The indicating scales may also be customized for a specific design need.

Surface-mounted Steel Enclosures
are used for housing the electronic circuit boards. The enclosures are manufactured to NEMA 12 specifications and have welded seams, external mounting feet and a solid neoprene cover gasket. The standard finish is grey polyurethane enamel over phosphatized and primed surface. Pressure connections are convenient bulkhead compression fittings suitable for 1/4" OD metallic or thermoplastic tubing. Electrical connections are made via a standard 1/2" electrical conduit connector.