Elgas DATCOM, Operating Instructions Manual

Page: 135 / 228

7
Technical Description of the Device
133
7.8.1 Downloading Application Firmware Using “Remote Download“
Method
Using this method, you can load new firmware to your device in accordance with the Welmec 7-2
Extension D recommendation. The loaded firmware is secured with a digital signature ,
separately in each section. This is to check the integrity of data, the authenticity and also the
specificity of the device. The upgrade process is divided into several phases, delayed start of the
firmware activation can be set. Information on processing of each individual phase of loading is
recorded in the settings archive.
Downloading the FW is not bound to a specific communication protocol or specific PC software,
and can be performed via any communication channel. For recording, the firmware is divided into
two parts; either the "App" part or the "App" part together with the "Metrolog" can be downloaded.
The digital signature contained in the application firmware file (* .srec) confirms that standard
testing has been performed at ELGAS, s.r.o. and that the "Metrolog" module complies with the
valid certificate of the relevant notified body.
7.8.2 Storing Data in the Device
Various memories (internal processor RAM, internal FLASH processor, SPI FRAM and SPI
dataFLASH) are used to store data in the device.
All the archives and counters are stored in 16MB
non-volatile SPI dataFLASH memory.
Important archives, counters and parameters are additionally backed up in other memories. All
data is properly secured. Irregular errors are indicated in the internal diagnostics of the device.
The backup battery in the device is used to back up the RAM and the RTC circuit remains in
operation. The pulses are counted at the LF inputs.
7.9 Principle of the Function
7.9.1 Conversion Using State Equation
The gas flow data is obtained by means of pulses (N) from the LF or HF sensor located in the
meter. From the number of pulses (N) and from the gas meter constant (kp), the volume is
calculated at the measurement conditions (V).
From the temperature and pressure transducers, the device receives additional gas flow data -
gas temperature (t) and absolute pressure under the measurement conditions (p). From this data,
the conversion number (C) is calculated, which is influenced by other factors: absolute
temperature under basic conditions (Tb), absolute pressure under basic conditions (pb) and gas
compressibility factors under basic conditions (Zb) and measurement conditions (Z) .
Volume under measurement conditions:
V =
N
k
p
Gas compressibility factor:
K =
Z
Z
b
Conversion factor:
C =
p
*
T
b
*
1
p
b
(t + 273.15) K
Volume at the basic conditions:
V
b
= V * C