88 January & February 2021 http://www.elektormagazine.com
The following steps will take quite some time.
At the end of each step saving of the new
values must be confirmed. Please note that
older parameters will be erased, even if the
new values are NOT saved.> PGA2: gain 3 calibration followed by
gain 10 calibration
> Calibration of the ranges 1 to 4
> <Open-circuit> Trim, all freq.
> <Short-circuit> Trim, all freq.
At the end of calibrations remove all jumpers
and connect the Kelvin cables or the test
fixture to the BNC connectors. Repeat
the open- and short-circuit Trim proce-
dure to take in account the new parasitic
components.Before a test, at a given frequency, it is possi-
ble and even recommended to make the two
corrections TRIM by pressing the correspond-
ing button (the second). New settings (as well
as those at other frequencies) can be backed
up by a long keypress of this button.Error checking
During the firmware start-up sequence,
some checks are performed. First, the
Bootloader checks the integrity of the
firmware in memory. Then the firmware
checks for valid language data in high
memory and verifies the supply voltages.
If the power supply check fails, the
message “Power supply Test Error, code
A” is displayed and the program loops on
a sequence with the D12 LED turned on for
½ s and off for 1 s. Each bit of the binary
equivalent number of A shows the state ofgold-plated contacts to minimize parasitic
resistance and disconnect all cables from
the BNC connectors. The complete calibra-
tion procedure is described in the download-
able documentation [1]. It is not difficult at all,
and requires only a multimeter, configuration
jumpers and a small trimming tool... and a
bit of patience because at some steps it will
take several minutes. We will only give you
an overview here.> Set sine generator offset (2a)
> Measured value of VRef (DDS) (2b)
> CMRR of voltage differential opamp
(2c/d)For inductances, after validation and a few
seconds for the stabilization, the actual value
of the current is displayed under the label
tance of the DUT. The label of the second
button changes, because the TRIM is no
longer possible with DC-bias. It changes to
BIAS 0 and pressing the button will switch
off the bias.
Calibration menu (Figure 2)
All calibration steps of the device are acces-
sible in the menu. If the first-time calibra-
tions are performed, it is recommended to
run them in the menu order. Use jumpers with
Table 2.Bit
number
UxThe bit is 0 if the
measured voltage
is1
-5V
-5.3V < Ux < -4.7V2
+5V
4.7V < Ux < 5.3V3
+3V
2.85V < Ux < 3.15V4
+6.5V
6.29V < Ux < 6.68V5
+7.5V
Figure 3: Controlling the LCR meter via the AU2019 app. 7.30V < Ux < 7.60VFigure 2: The Calibration Menu.
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