Measurement Specialties 9116 - Manual (Page 33)

Pressure Systems, Inc. Model 9116 User’s Manual
Page 24 www.PressureSystems.com
3.1.4.1 Startup Initialization
Since power supplies may be distributed widely across a network of modules and host
computer(s), it is not uncommon for modules (singly or together) and the host to lose power
independently. Thus, their power may be restored at different times. Startup initialization, for
every module, must normally be performed when its power is restored, as each module enters
default states after power-up, which may not be the state the host computer had previously
been operating in. Any previous TCP/IP socket connection is also lost after power failure and
must be re-established between host and module before any TCP/IP commands can be
recognized by the module. These commands are generally used to detect that startup
initialization has occurred (or to force reset at other times), after which other commands may be
used to restore the original operating condition.
With Model 9116 modules, the Power-Up Clear (‘A’) command is used as a simple command
to elicit a known response from a module. Although this causes no internal function within the
module, it will result in an acknowledgment being returned to the host computer to verify proper
communications. The best way to detect that a power reset has occurred in a module is to
notice that the TCP/IP socket connection is no longer valid. At any point during module
operation, the Reset (‘B’) command may be used to return any module to its default “reset”
state. If the module is then required to enter any other states (that were previously programmed
for it by the host), the host must then restore these states accordingly using the appropriate
commands. This reset command simply returns internal software parameters to a default state
(as after power up or reboot). It will not close the existing TCP/IP socket (as will power up or
reboot).
The Set/Do Operating Options/Functions (‘w’) command has many purposes, but may first
be utilized during the module initialization stage. It may also be executed at any time during
data acquisition. However, some non-factory-default options of ‘w’ may become the new reset
default, if a particular function is used to establish them in non-volatile memory.
If any form of the Configure/Control Autonomous Host Streams (‘c’) command or the
Configure/Control Multi-Point Calibration (‘C’) command was in use before reset, it must be
executed again after the reset to restore it. Any other command, that establishes the module in
a non-default reset state, must be re-executed after a reset, if processing is to continue in that
state.
The Network Query (“psi9000”) UDP/IP command may be used (at any time) to make each
module on the network identify itself to the host(s). A parameter, returned in each module’s
response, indicates whether or not a module still has a valid connection. This is a useful way to
detect if an overt reset occurs in a module. The module may be configured to emit this
response automatically after any reset (power on or reboot).
3.1.4.2
Module Data Acquisition
After power-up, all modules will begin to scan all attached transducer channels in channel
number order. Scanning will occur at the module’s maximum internal rate (using the previously
stored number of data averages per channel). The data are stored in an internal buffer,
available for retrieval by the host computer. Engineering units conversion of the scanned
channels is accomplished using thermal correction data extracted from each transducer at
power-up. While scanning, the module will automatically monitor the attached transducer’s
temperature, correcting engineering unit output for any temperature effects.