Service Information
5-9
Calibration errors
One of the errors listed in Table 5-4 may occur during the
course of calibration. (These errors will appear on the
front panel and may be obtained over the bus by using the
:SYST:ERR? query.) The most likely causes of these
errors are:
•
Incorrect connections.
•
Wrong calibrator voltage setting.
•
Improper low-thermal divider setting.
Viewing and changing calibration dates
Preamplifier calibration dates can be viewed or changed
by using the CALIBRATION-DATES selection in the
PREAMP CAL MENU. To change dates, simply follow
the prompts on the display.
5.2.7 Gain constants calibration
The gain constants method of calibration provides a
simple method of transferring the calibration constants
stored in one power supply card to a different power
supply card. This feature is useful in situations where a
preamplifier module is to be used with a power supply
card other than the one with which it was originally
calibrated, and it eliminates having to perform normal
calibration whenever a preamplifier module is moved
from one power supply card to another.
To use this method, first read the gain constants from the
power supply card originally used when calibrating the
preamplifier, then store the constants in the new power
supply card. The basic procedures for reading and storing
constants are explained in the following paragraphs.
Reading gain constants
There are three gain constants that are derived during nor-
mal calibration:
•
G1K:
×
1,000 gain constant
•
G10K:
×
10,000 gain constant
•
G100K:
×
100,000 gain constant
These constants can be read from the front panel or over
bus, as outlined below.
■
Reading Constants from the Front Panel
To read gain constants from the front panel, select
ENTER-CAL-CONSTANTS in the PREAMP CAL
MENU, then press ENTER. Select the desired constant to
display, then press ENTER. The unit will then display the
present value of the constant. For example, the
×
1,000
gain constant may appear as follows:
G1k = 1.0000000
Repeat the process for the other two constants, and record
their values for storage in the other power supply card.
■
Reading Constants Over the IEEE-488 Bus
To read constants over the bus, first send the appropriate
query:
:CAL:UNPR:PRE:G1K?
(
×
1,000 gain constant)
:CAL:UNPR:PRE:G10K?
(
×
10,000 gain constant)
:CAL:UNPR:PRE:G100K?
(
×
100,000 gain constant)
After sending the query, address the instrument to talk in
the usual manner, then input the constant into a conve-
nient floating-point numeric variable. Constants are
returned in standard floating-point format.
Table 5-4
Preamplifier calibration errors
Error ID code
Error message
+445
+446
+447
Preamp 1k gain out of spec
Preamp 10k gain out of spec
Preamp 100k gain out of spec