CẢM BIẾN ÁP SUẤT DẠNG CHÊNH ÁP APLISENS MODEL APM-2

Application and construction

Modular electronic differential pressure transmitter APM-2 is applicable to hydrostatic measure of level in closed tanks, density or phase boundary. The measuring system consists of 3 separate modules – central unit and two absolute pressure transmitters. Level is calculated in central unit basing on measurement from two pressure transmitters. High pressure transmitter measures hydrostatic pressure of liquid in tank, low pressure transmitter measures pressure of gases above the liquid. Differential pressure is calculated in the central unit. With default settings of central unit function of high pressure transmitter is designed for transmitter directly connected with central unit (PC1). User can change this assignment to second transmitter by changing

configuration in central unit in local menu or via HART protocol. Measuring points can be several dozen meters apart.

The casing of central units is made of aluminium alloy cast or stainless steel with degree of protection IP66 or IP67 equipped with local display and buttons for configuration. Measuring element of each of absolute pressure transmitters is piezoresistant silicon sensor separated from the medium by diaphragm and manometric liquid. Process connection of absolute pressure transmitters can be diaphragm seal or threaded flush connection. By using diaphragm seals transmitters can be used for measurement of contaminated medium, medium with high viscosity, very hot or very cold medium or medium where sanitary process connection is needed.

Electronic units of pressure transmitters are closed in sealed stainless steel casings with degree of protection IP67.

All modules of measuring system are connected with electric cables (length of cables is specified by user). This system is an alternative for differential pressure transmitter with two remote diaphragm seals connected with capillaries filed with silicon oil uses in measurement of level on closed tank. The advantage of APM-2 is modularity of measuring system. By using M12 connection in case of any malfunction user has possibility to replace each of tree modules. Furthermore measurement is free of additional errors caused on the temperature gradient in the oil-based diaphragm sealing system. APM-2 transmitter gives not only information about differential pressure but also about static pressure and temperature (both transmitters and central unit)

Technical data

Accuracy Ł ±0,1%

Long term stability Ł accuracy for 3 years

(for the nominal measuring range)

Thermal error (including errors from diaphragm seal) < ±0,1% (FSO) / 10°C

Thermal compensation range -25...80°C

Processing time (calculation cycle period) 0,5 s

Additional electronic damping 0...60 s (factory setting: 5 s)

Error due to supply voltage changes 0,002% (FSO) / V

Electrical parameters

Power supply (standard version) 13...55 V DC

Output signal 4 ¸ 20 mA +Hart 7

Load resistance

Resistance required for communication min 240 W

Operating conditions

Operating temperature range (ambient temp.) -30...85°C special version -40...85°C

Maximum medium temperature 150°C special version 200°C

Construction, materials

Wetted parts acc. to diaphragm seal datasheets

Casing:

central unit Aluminium

option: SS316

pressure transmitters SS304

Ingress protection class IP67