Introduction; Product Overview; Hardware Description - Honeywell HPB User Manual

Precision barometer rs-232 and rs-485 output

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HPB/HPA User Manual

1 Introduction

The Honeywell Precision Barometer RS-232 and Honeywell Precision Barometer RS-485* (HPB) provides high

accuracy absolute pressure readings in digital form. The first-time user will be able to use the HPB within minutes,

yet capability exists to configure the HPB for optimum performance in specific applications.

The heart of the HPB measuring system is a silicon piezoresistive sensor, which contains both pressure and

temperature-sensitive elements. Digital signals representing temperature and pressure are processed by a

microprocessor to produce fully temperature compensated and calibrated pressure readings over the entire -40 to

85°C temperature range.

Any computer having a serial port and terminal emulation software can be connected to the HPB to allow the user

to select baud rates, sample rates, readout resolution, units of pressure and other choices. RS-485 versions

require an RS-485 to RS-232 converter or and RS-485 port on the computer. User selected functions are set

through the digital interface. The selected functions may either be used temporarily, until the HPB is powered

down, or may be stored in the internal EEPROM to automatically configure the HPB each time power is applied.

The HPB receives commands and sends data from either an RS-232 port or a multidrop RS-485 port. Using the

RS-232 type HPB, up to 89 units can be connected in a ring configuration to a single serial port of a computer. The

type HPB allows up to 89 HPBs to be connected to a two-wire multidrop bus, when bus repeaters are used to

satisfy the RS-485 bus electrical requirements. Group (multicast) addressing allows up to nine groups of HPBs to

be addressed with a single command. Global (broadcast) addressing will send a command to all HPBs on the

serial bus.

See Sections 8 and 9.

* For simplicity, references throughout this manual HPB-RS-232, HPB-RS-485, HPA-RS-232 & HPA-RS-485 have been

shortened to HPB.

RS-485

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