Introduction - Tektronix DM2510 Service Procedure

Introduction
WARNING
To prevent a shock hazard, do not exceed 1000V peak
between input low and chassis ground . Some of the
procedures in this section may expose the user to
dangerous voltages. Use standard safety precautions
when such dangerous voltages are encountered.
The DM2510G and DM2510 are software calibrated by constants that are stored
in EEPROM . Every range has its own calibration values : an offset and a gain .
In this way, there is no interference between ranges ;
re - calibrating one range ,
will not change other ranges .
All DC voltage and DC current ranges have a
positive and a negative offset value , and a positive and a negative gain .
When
taking a measurement , the offset value is first subtracted from the measurement
counts that are measured by the microcontroller .
The result is multiplied by
the gain to get the display value.
There is a GPIB query " CALFACTOR" that will output the calibration settings
per range .
In AC ranges, calibration is done at 5 % and 95 % of full scale , because of
reduced
accuracy
of
true RMS converter with
small signals .
For the
microcontroller to be able to convert these two calibration measurements to the
standard offset and gain , both measurements need to be known .
For that
reason , calibration of AC ranges needs to be done in a specific order.
The 5 % of full scale calibration needs to be done first , immediately followed
by the 95 % calibration of that same range .
Only after that, the new offset and
gain values will be checked , and written to EEPROM .
Obviously , for proper calibration of both gain and offset , it is necessary to do
the offset calibration of a range before the gain calibration .
DM2510 / DM2510G
Page 6 of 17
In normal measurement , before the settings read from EEPROM are used , the
firmware compares the offset and the gain with values in a table . When one of
the EEPROM settings of a range is not within these boundaries , the DMM will
consider that range to be uncalibrated .
Adjustment Procedure
May 6 , 1994
Revision A
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