Sensors & Transducers e-Digest, Vol. 77, Issue 3, March 2007: Product News
(ISSN 1726- 5479)
HVAC/R Pressure Sensors
American Sensor Technologies, Inc. (AST) offers a variety of HVAC/R pressure products for integration into HVAC and refrigeration equipment. These HVAC/R pressure sensors incorporate a one-piece, stainless steel construction that contains no internal seals or gaskets, eliminating the chance of permeation, system contamination and freezing in HVAC and refrigeration applications. Sensors also feature a high cyclical life (>100 million full cycles), long-term stability and compound ranges with linear output through zero (i.e. -14.7 to 100PSI).
Each HVAC/R pressure sensor also ensures a high level of EMI/RFI protection, in addition to holding hazardous area approvals [for equipment installations in classified locations], RoHS compliance [when requested] and a listing under UL/cUL standards.
AST’ HVAC/R pressure products offer a successful solution to customers’ ammonia refrigeration pressure measurement requirements. Many refrigeration pump and compressor manufacturers are replacing freon with more efficient, ammonia-based systems. However, the thermodynamic behavior of ammonia is very different from freon. When the refrigeration pump turns on, the ammonia temperature rapidly changes from 100 F to -70 F or below. This accelerated change, along with the types of sensor diaphragm materials, effects pressure transducer performance and, ultimately, the control system.
O-ring sealed pressure sensors cannot withstand rapid thermal changes and, over time, the internal O-ring will fail. Fluid filled sensors suffer from freezing effects, which lead to the rupture of the diaphragm membrane. Thin film sensors [based on 15-5 and 17-4PH stainless steels] that have their diaphragm welded to a pressure port, undergo thermal stresses that eventually crack the steel.
Thermal Flash Protection™, applied by AST to its HVAC/R pressure sensors, reduces the effects of thermal flash transients when the media is ammonia. First, AST utilizes its one-piece stainless steel sensing element, with 316L wetted materials, which is free of welds, oil-fill and internal O-rings. Next, a special non-clogging port design is used to minimize the extreme temperature change. The sensor will recognize a uniform temperature as to maintain system stability. Ultimately, Thermal Flash Protection™ is the pressure sensing technology for ammonia refrigeration applications.
AST offers HVAC/R solutions with an SAE4 (7/16-20 UNF) female pressure port that contains an internal Schraeder depressor pin. This port allows the sensor to be easily removed or installed in service, eventually eliminating the need for adaptors. AST manufactures additional pressure ports, such as 1/8" NPT, 1/4" NPT and SAE4 male.
AST HVAC/R pressure products are ideal for use in refrigeration pump controls, chillers, freon and ammonia cooling systems, high pressure wells, boiler controllers and environmental testing.
Karmjit S. Sidhu,
American Sensor Technologies, Inc.,
450 Clark Drive, Mt. Olive, NJ 07828
Fax: (973) 448-1905
1999 - 2007 Copyright ©, International Frequency Sensor Association (IFSA). All Rights Reserved.