Elektor_Mag_-_January-February_2021

lektor January & February 2021 89

positive terminals of this bias voltage are J4/

J5. Capacitance must be the dominant part of

the impedance, otherwise the LCR meter will

automatically switch off the DC-bias voltage!

Capacitor (Figure 5)

For a capacitor it is possible to superimpose

a DC voltage between 0.0 V and 5.0 V on the

test signal, see the paragraph on DC bias. The

one of the verified supply voltages: 0 if the
voltage is correct, otherwise 1 (Table 2).

PC Mode
Start the device in PC mode (“Waiting for
the GUI...” is displayed), and a few seconds
later start the AU2019 program on the PC
(Figure  3 ). In the Port menu, select the correct
serial port, then click the Open port button.
Once the communication is established, the
firmware version will be displayed to the right
of the LCR Meter AU2019 app version. After a
short time, all parameters of the DUT will be
displayed. The buttons act as for the stand-
alone mode.

Some menus are specific to the PC mode,
others are the same as those of the stand-
alone mode, all this is explained in the
documentation. There are also instructions
for firmware and menu text updates. A full
description can be found in the Operating
instructions document [1].

How to measure components
Test fixtures have a predominant influence
when measuring at the end of the measur-
ing range and/or at high frequencies. Special
attention will be paid to the TRIM procedures.
In order for the measurement to be accurate
when the DUT is a low inductance or resis-
tance, it is important that the TRIM short-cir-
cuit compensation is performed just before
the measurement is made. The same goes
for low capacity, in this case with the TRIM
open-circuit compensation.

Resistor (Figure 4)
In most cases, resistors can be measured
with a good multimeter! On the other hand,
it may be interesting to know the parasitic
series inductance of a low ohm resistor at
high frequencies, or the parasitic capacitance
of high value resistor.

Figure 5a: Measuring a small capacitor at higher
frequency.

Figure 5b: Measuring a large capacitor at low

frequency.

Figure 5c: Measuring a large capacitor at low

frequency and 5 VDC bias.

a

Figure 4a: Measuring low-ohm resistor at high

frequency.

Figure 4b: Measuring high-ohm resistor at low

frequency.

a b

b c

COMPARISON WITH COMMERCIAL EQUIPMENT

Of course, it is a good idea to compare this A2019 LCR meter with commercially

available equipment. Unfortunately, neither the designer nor the Elektor Lab had

equipment available to do a comparative test and even worse: it is very difficult to

find an LCR meter with measuring frequencies up to 2 MHz. With the kind help and

assistance of Alfred Rosenkränzer, the AU2019 was compared to a Hameg HM8118

and an HP/Agilent 4263B and a handheld Keysight U1732A, the Hameg with the

highest measuring frequency of 200 kHz. His overall conclusions are the following:

The AU2019 has become quite a good measuring device. At some points it has

difficulties (for example, with small coils at 100Hz measuring frequency). This is

certainly not the ideal frequency to measure such small coils, the Hameg and HP

produced quite sensible values there.

It is nice that you can buy the Kelvin cables and the TH26001A 4 terminal test

fixture very cheaply on Ebay, but it is difficult to say how good the quality is. A good

connection between component and LCR meter is the key to a stable measurement.

The 16047E test fixture (same type of device as the TH26001A) is very useful.

It can be said that the overall accuracy of the AU2019 is 1%, and up to 0.1% for values

in the middle of the measurement range, by selecting the correct measurement

conditions in relation to the type and value of the component.