Panametrics HydroProII, Руководство пользователя

Страница: 27 / 104

HygroPro
II
User's Manual 15
Chapter 1. Installation
1.6 Software Setup
The HygroPro
II
is shipped from the factory with HART enabled and configured for point-to-point communication. The
HART interface for the device allows for setting up 4 dynamic variables, calibration of the HART DAC and limited
programming of the instrument configuration parameters. The device provides three process variables: moisture,
temperature, and pressure. Note that some device functions are not available via HART communication.
Three sets of commands - Universal HART commands, Common practice HART commands, and Device specific HART
commands – are supported by the HygroPro
II
. Universal commands are supported by all HART compatible devices.
Common practice commands are commands that every field device is expected to support. Device specific
commands are specific to the device. For a detailed description of the HygroPro
II
device specific commands, refer to
the HART Field Device specification (FDS) in Appendix A.
1.7 Standard DD File
The Device Description file (rev A) for the HygroPro
II
field device for HART 7 is available from the FieldComm Group
web site www.fieldcommgroup.org . A Device Description ("DD") is a formal description of the data and operating
procedures for a field device, including commands, menus and display formats. It describes exactly what you can do
to that particular device by HART communication.
It is written as plain text, but is converted into a coded ("tokenised") form for use, for greater efficiency. The DD file
contains the standard table view and enhanced view.
The main things the DD describes are Variables, Commands, Methods and Menus. Every accessible variable in the
device is included. That means the process measurements, any derived values, and all the internal parameters such
as range, sensor type, choice of linearization, materials of construction, etc.
For each Variable, the DD specifies, among other things, the data type (e.g., integer, floating point, alphanumeric,
enumerated), how it should be displayed, a name for display to an operator, any associated units, and help text,
perhaps describing the meaning of the variable or how it is used.
For each Command, the DD specifies the data structure of the command and its response, and the meaning of any
command response status bits.
Methods describe operating procedures, so that a user can be guided through a sequence of actions, for example to
re-calibrate the moisture or pressure sensor.
Table 6: Valid HART Parameters and Units
Description Unit Format Access Type
Dew point Dp °C fp R
Dew point Dp °F fp R
Dew point Dp °C Equip fp R
ppmw ppmw fp R
Scale low fp R/W
Scale high fp R/W
Output
measurement
fp R/W
Output Unit int R/W
Output mode int R/W
Format: fp = IEEE floating point, int = integer, uchar = unsigned character,
ucharX = X bytes of unsigned characters.
R/W/B:R = read only, W = write only, B = read or write using HART
Valid HART Parameters and Units