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Instrument Security Procedures
Fluke 5790A

Product Name:
AC Measurement Standard

Memory Description:
The Fluke 5790A AC Measurement Standard contains two types of storage
media. The first is a flash-based storage media and the second is random access
memory (RAM).

Flash Memory:
The flash memory used in the 5790A is a physically block structured device. It
contains three (3) separate blocks. The first block is a special purpose block
intended to hold a small boot loader. It's used for that purpose within the 5790A.
The boot loader software was designed and maintained by the Fluke Corporation
and is preprogrammed into the flash device for us by the vendor. The boot loader
flash memory can't be easily changed or reconfigured without special
programming equipment. It's considered by Fluke to be permanent. If it were
tampered with, or otherwise changed, by anyone other than qualified software
engineer equipped with supporting documentation from Fluke, and external
programming hardware, the AC Measurement Standard would cease to function.
The second block contains the application software for the 5790A. It's
programmed by Fluke but is otherwise subject to the same stringent restrictions
as the boot code. Additionally, a checksum is generated and compared on
power-up to insure that no changes to this code have occurred. The third block is
logically partitioned, by the software, into two (2) mini-blocks. The first contains
the calibration constants for the instrument. The second contains all nonvolatile
configuration data for the instrument.

Calibration Constants:
Calibration constants are double precision floating-point numbers. These
numbers are used by the instrument during normal operations to achieve its
rated output accuracy. Each calibration constant (CCO) has a default value and a
limit. Most limits are within a few percent of the default value. It's impossible to
set a calibration constant to a number outside of its limit. Calibration constants
can't be accessed directly by a user. They can be changed during a calibration
process. Theoretically, someone could run a calibration procedure and store
numerically encoded data in the calibration constants. The limits on many of
them would obviously complicate the process though.

Non-Volatile Configuration Data:
Non-Volatile configuration data contains user settings like IEEE address, serial
port configuration, calibration dates, etc. It also contains a string of a maximum of

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63 characters. The string is an IEEE 488.2 standard and is set using the <*PUD>
command. It's queried using the <*PUD?> Command or from the front panel [see
page 6-3 of the Operator Manual for a complete explanation of these

To read the contents of the User Report String [PUD], use the
following key strokes from the front panel [see page 3-15 of the
Operator Manual]:

Using the blue `soft' keys under the Control Display, select the


The Control Display then shows the user report string contents.

Random Access Memory (RAM):
RAM is not directly accessible by the user and its contents are lost when the
power is removed (volatile). RAM is not a likely security risk.

Memory Cleaning Instructions:
The PUD string can be cleared using the <*PUD> command in conjunction with
an empty string. Then queried to insure it contained the empty string. This would
not address any of the other nonvolatile constants but would remove the most
likely threat.
All Configuration Data, including the User Report String, can be set to their
default state using the command and . Any configuration
data that has been modified by the customer would need to be restored,
including the system clock and clock format. This would eliminate any risk of
tampering with the Configuration Data Constants but would not address the
Calibration Constants issue. The Calibration Constants can be reset to their
default settings using the command and . The instrument
would need to be calibrated after these commands were issued. This would
address the Calibration Constant issue but would not affect the Configuration
Data Constants. All data in the third physical block, the Configuration Data and
the Calibration constants, can be reset to their default state by using the
command and the parameter [see page 4-25, 26 of the
Operator Manual for a complete explanation of this command and its
parameters]. The and parameters require the calibration switch on
the rear panel of the instrument be set to the ENABLE position.

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For re-formatting non-volatile memory, use the following key
strokes from the front panel [see page 4-25 of the Operator

Select the SETUP key on the front panel,
Using the blue `soft' keys under the Control Display, select the

The instrument will need to be calibrated after this operation and any
configuration data that has been modified by the customer would need to be
restored, including the system clock and the clock format. This is the safest
method, but is highly destructive in that it requires a total recalibration of the

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