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Diagnostic Testing and Troubleshooting (2635A)
Calibration Failures
5A
5A-29
5A-23. Retrieving Calibration Constants
If a calibration error is suspected, the stored constant can be retrieved and verified over
the computer interface. Acceptable calibration constants for each function and range are
listed in Table 5A-9. Retrieve the constant with the following command:
CAL_CONST? xx (where xx denotes the calibration constant number)
The entire calibration of the Hydra Databucket can be retrieved from the instrument in
tabular form by using the following command:
EEM_LIST?
The instrument response from this command shows the currently used FLASH memory
block and page numbers, and each calibration constant in hexadecimal and floating point
with a description of what function and range each calibration constant is used on. The
following is a sample of a typical EEM_LIST? response:
Page 10 of Parameter Block 1 is currently in use.
Register Hex Value F.P. Value Description
---------------------------------------------------------------
0-1 0x3F8A847A1. 0821679100 Millivolt DC Gain
2-3 0x3F8A5D751. 08097711 Volt DC Gain
4-5 0x3F8A63571. 0811566300 Millivolt DC Gain
6-7 0x3F8A5BC01. 08092503 Volt DC Gain
8-9 0x3F8B4F571. 088358830 Volt DC Gain
10-11 0x3F8A7C8A1. 0819256150/300 Volt DC Gain
12-13 0xB8F20A00 -0.0001154300 Millivolt AC Offset
14-15 0x3F8A51191. 0805999300 Millivolt AC Gain
16-17 0xBA974800 -0.00115423 Volt AC Offset
18-19 0x3F8A7F291. 08200563 Volt AC Gain
20-21 0xBC3A6C00 -0.011378330 Volt AC Offset
22-23 0x3F8A863A1. 082221330 Volt AC Gain
24-25 0xBDE81400 -0.1133194150/300 Volt AC Offset
26-27 0x3F8AC8861. 0842445150/300 Volt AC Gain
28-29 0x3F808EAB1. 0043539 300 Ohm Gain
30-31 0x3F8097591. 0046188 3 Kilo Ohm Gain
32-33 0x3F80FD781. 0077353 30 Kilo Ohm Gain
34-35 0x3F7FF46C0. 9998233 300 Kilo Ohm Gain
36-37 0x3F7FFDD00. 9999666 3 Mega Ohm Gain
38-39 0x3F7FFDD00. 9999666 10/30 Mega Ohm Gain
40-41 0x3F80073D1. 0002209 Frequency Gain
42 0x000F Calibration Status
43-44 0xAAAAAAAA Product Serial Number
45 0xFFFF Unused EEM Register #1
46 0xFFFF Unused EEM Register #2
47 0xFFFF Unused EEM Register #3
48 0x62F4 CRC of EEM Data (0x62F4)
5A-24. Replacing the Flash Memory (A1U14 and A1U16)
The FLASH Memory provides nonvolatile storage for the instrument serial number, the
instrument firmware, and all calibration information. If the "boot" firmware in FLASH
memory has been determined to be faulty, A1U14 and A1U16 must both be replaced.
Many other problems may be corrected by loading new instrument firmware in the
instrument (see the section entitled "Updating the 2635A Instrument Firmware" in
Section 4 of this manual), or recalibrating the instrument.
If the FLASH Memories must be replaced during repair, the instrument must be
recalibrated. The new FLASH Memory can be programmed with the 7-digit serial
number found on the rear panel of the instrument or any 7-digit identifier of your
choosing. Note that the serial number is not programmed prior to shipment from the
factory.