Siemens MD-12HD, User Manual, Page: 47 / 74

Siemens Industry, inc. 46
12 Volt Auxiliary Power
The MD-xxHD meter provides an auxiliary 12 volt output that is derived from an auxiliary winding on the
MD-
xxHD’s line-connected power supply. The 12 volt supply voltage is
unregulated but protected by a
self-resetting fuse. The purpose of the supply is to power external radio equipment or provide supply
voltage for analog sensors, such as 4 to 20 mA current loop devices. If full-rated current is drawn from
this terminal, the minimum operating voltage of the L1-L2 power supply is 100 Vac.
Access Restriction Limitations
If security levels have been set up in the meter, no data is accessible through the LCD user interface or
MD-xxHD Web App without entering the PIN credentials. Note, however, that protocols such as Modbus
do NOT SUPPORT ANY LEVEL OF security such that any network traffic acting as a master can retrieve
and write data from the registers. Generally, this will require knowledge of the IP address or slave ID and
the register list which discourages casual intrusion.
Security PIN Protection
MD-xxHD meters have two levels of PIN protection that users can choose to assign for restricting access
to meter information. The PIN logic is described in the figure below. The
default user entry (on power up
or time-out) is 0000 which satisfies both the Read Only and the Read/Write default register settings.
Using the Permission Registers
The MD-xxHD
meter uses both a “Read Only” register and a “Read/Write” register to compare against
user entrees from the LCD keypad or MD-xxHD Web App form entry. Both internal permission registers
have a default value of [
0000 ]. A consequence of this is that both PIN registers need to be configured (i.e.
changed from defaults) to implement a read only PIN, otherwise the situation may occur where a user