CRESSTO - SP series - datasheet - differential low pressure transmitter0 pages

CRESSTO

pressure transmitter with autozeroing
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excellent long-term stability
very high sensitivity
overpressure endurance
uP signal processing
users SW configuration
analogue, digital and two-state
outputs
supply 5 ÷ 36 V
robust construction
protection IP65
wide temperature range
display fit-out possibility

These pressure transducers are designed for low and very low
pressures and pressure differences measuring. They may be used
in wide application in a branch of air-conditioning, ventilation,
combustion process control, clean rooms monitoring, equipment
design, etc. These transmitters can measure positive and/or
negative pressure differences or overpressure and/or underpressure against ambient atmosphere. The instrument is fitted with small
additional solenoid valve, which is controlled by the internal
program. This valve periodically disconnects pressure inputs of the
pressure sensor for 300ms period, when offset correction is
measured and recalculated. Autozeroing period can be set from 10
minutes up to 256 hours or can be switched-off. This principle is
functional even in two-wire loop 4-20mA.
The medium being measured may be a non-aggressive gas; some
exceptions must be consulted with producer. Measured media is in
a contact directly with silicon diaphragm, nickel plated brass,
silicone rubber, plastics polyetherimid. Pressure connections are
optional.
All components of the transmitter are placed in robust box from
aluminum alloy, which serves as a good mechanical and electrical
protection. The box is fixed by two screws, which are accessible
after disclosure the lid and are out of the sealed internal space, so
that protection is IP65. For electrical connection serves internal
terminal block with screws for cable with metal grommet PG-9.
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 output is independent on work position. Electronic

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circuitry is realized by a surface mount technology and for increasing protection is passivated by a coat.
Electric signal from sensor is after amplifying converted by 16bit
ADC to digital format. By means of two-dimensional polynomial
approximation of 3rd order transmitter is calibrated and temperature compensated. With special agreement it is possible to compensate down to -20°C. Output pressure value can be read directly
via serial port RS485, RS 232 or USB. Transmitter has special
output stage, which convert calculated value to analogue value
4-20mA (two-wire) or 0-20mA, 0-10V, 0-3V(three-wire). Particular
analogue outputs can be switch by software and it is possible to
change measuring pressure range and set other parameters, for
example damping etc. In addition it is possible at analogue outputs
to switch linear conversion characteristics to switching two-state
one and realize logic levels with voltage output. Transmitters can
be fitted with output switching module, which has small relay with
one contact and two independent outputs with NPN transistors with
open collector with LED indication. All switching parameters can be
set only via software. Next option is 4 or 5 digit LCD with white LED
back lighting. There is also place for FLASH memory, where can be
stored measured data with desired period (without timestamps).
Transmitters can be supply with DC voltage with wide range from 5
to 35 Volts. Change in this range has no effect to measurement
accuracy.
Software configuration is realized via special USB adapter with
program for Windows. Transmitter can be supplied from USB and
due to adapter totally DC isolation can be connected to PC whenever in the final application.

Hasičská 2643, 756 61 Rožnov p. Radh., CZECH REPUBLIC
tel.: +420 571 843 162, 571 845 338, fax: +420 571 842 616
e-mail: firma@cressto.cz
www.CRESSTO.cz