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ADS-14221, PPT2 User Manual
October, 2016
1.0 Product Overview
The Honeywell Model PPT2 Precision Pressure Transducers provide high accuracy pressure readings in both
digital and analog form. The first-time user will be able to use the PPT2 within minutes, yet capability exists to
configure the PPT2 to optimize performance in the User's specific applications. Throughout this User's Manual,
the PPT2 may be referred to as Precision Pressure Transducer.
The heart of the PPT2 measuring system is a silicon piezoresistive sensor which contains both pressure and
temperature-sensitive elements. Digital signals representing temperature and pressure are processed by the
PPT2 microprocessor to produce calibrated, temperature-compensated pressure readings over the entire
operating temperature and pressure range.
Both the analog and digital outputs are internally corrected over the full operating range. The PPT2 has a digital
accuracy of 0.075% of full scale (FS). Note that full scale for a 20 psig and a 20 psia is 20 psi, but for a 20 psid it
is 40 psi, the sum of + Full scale and – Full Scale. This is important to note when determining the accuracy
allowance.
The PPT2 receives commands and sends digital data using either an RS-232 serial port or a multi-drop RS-485
serial port of a computer. (Note: many newer computers will have only USB ports, no RS-232 or RS-485 ports. A
USB converter can be used to provide the required RS-232 or RS-485 port.)
Using the RS-232 type PPT2, up to 89 units can be connected in a ring configuration to a single serial port of a
computer. The RS-485 type PPT2 allows up to 89 PPT2's to be connected to a two-wire multi-drop bus. Group
(multicast) addressing allows up to nine groups of PPT2's to be addressed with a single command. Global
(broadcast) addressing will send a command to all PPT2's on the serial bus.
Any computer having a serial port and terminal emulation software can be connected to the PPT2 to allow the
user to set baud rates, reading rates, reading resolution, units of pressure and other choices. (User modified
functions must be set through the digital interface, using a computer with a serial port). The user-modified
functions may either be used temporarily, until the PPT2 is powered down, or may be stored in the PPT2 internal
EEPROM to automatically configure the PPT2 each time power is applied.
Analog output from the PPT2 16-bit digital-to-analog converter may be obtained without a host computer.
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