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Emerson Climate Technologies

Electronic Valves & Controls

Emerson Climate Technologies

Pressure Transmitter – PT4

The heart of the transmitter is a pressure sensitive

piezo resistive cell. This is surrounded by an oil cushion

enclosed by a stainless steel diaphragm. The integrated

electronic module conditions the output of the pressure

cell to produce a temperature compensated signal of

4…20 mA.

The pressure cell consists of a silicon diaphragm with

strain gauges diffused into it. A particular advantage of

using silicon is its good hysteresis and creeping behav-

ior. The direct integration of the strain gauges means

that no additional errors can be introduced between the

location where the pressure acts and where it is mea-

sured.

Separation of the pressure sensitive element by the

oil cushion protects the sensor cell against external me-

chanical loads such as vibrations, pressure pulsations.

This ensures reliable operation and a long life-time

expectation even under severe operating conditions.

Electronic

Board

Stainless Steel

Diaphragm

Sensor

Oil Cushion

PRESSURE

The protective stainless steel diaphragm ensures

compatibility with the media frequently encountered in

refrigeration systems. The outside of the PT4 consists

of a corrosion resistant stainless steel enclosure. It is

sealed at the electrical connector socket and at the

pressure connector joint. This way, the PT4 meets the

requirements of IP65.

The sensor works internally as an absolute measur-

ing device. However, it is calibrated to produce a relative

output signal assuming an ambient pressure of 14.5 psi.

When using PT4 in heights signicantly above sea level

the output signal deviation must be taken into account.

i.e. at a height of 1000m the signal reads approximately

1 psi lower than the actual pressure.

Short-term protection against wrong polarity is pro-

vided by an internal diode, up to 33 Vdc for the 4...20

mA output version PT4.

PT4 is compliant with the present electromagnetic

compatibility legislation and in particular with the EMC

directives 89/336/EC complying with EN-61000-6-2, EN-

61000-6-3, EN-61000-6-4.

Pressure transmitters PT4 with current output (two

wire connection) offer the following advantages:

• More suitable for signal transmission over long

distance.

• Higher immunity to electro-magnetic interference.

• Open circuit detection enables fail-safe operation.

PT4 – PRESSURE TRANSMITTER

TXV Controller – EC3-X32

EC3-X32 is a stand-alone universal superheat con-

troller for air conditioning, refrigeration and industrial

applications such as chillers, industrial process cool-

ing, rooftops, heat pumps, package unit, close control,

cold room, food process and air driers. EC3-X32 offers

remote access with built-in TCP/IP Ethernet commu-

nications and WebServer functionality. Any standard

WebBrowser (e.g. Internet Explorer® 5.0 or higher or

Mozilla Firefox) can be used for monitoring or parameter

setting.

EC3-X32

The EC3-X32 controls the opening of an electrical

control valve according to desired superheat. As Emer-

son Electrical Control Valves (ECV) are able to provide

a positive shut-off function better than conventional

solenoid valves, there will be no ow through Emerson

ECV as long as the compressor is not running. In the

event of cooling request and compressor start-up, EC3-

X32 needs to be informed. This can be achieved by a

digital input. EC3-X32 will start to control the refrigerant

mass ow stand alone by precise positioning of the ECV

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