LQ-9101
User Manual
CAUTION The pins must be shortest. Large-capacity capacitors have low capacitive reactance at
high frequencies. Pin parasitic inductances of several tens of nH have a significant effect on capacitive
reactance, capacitive reactance is partially offset by parasitic inductance, and capacitive reactance
decreases. As a result, the resulting capacity value is large, and bulk capacitors are When the frequency is
low, this situation is not obvious and low frequency measurements should be selected.
7.4 Insert a short-circuit copper wire on the socket, showing tens of nH inductors, change the wire with a
relatively short and thick thickness, and show a much larger inductance.
This is not related to the watch. The wire is a ferromagnetic material and it is imagined as a coil. More
iron core to understand.
7.5 What is the selection of the series model in parallel?
In general, the nominal value of the low-impedance element is the equivalent value in series, and the
nominal value of the high-impedance element is the parallel equivalent value. When verifying the failure
of a single component, it is consistent with the manufacturer's model under the nominal conditions. If the
series model parameters are referred to in the 47uF electrolysis product specification, then the series
model parameter measurements must be read.
The equivalent value of the series equivalent parameter and the parallel equivalent parameter at the
same frequency are the same, which is to say, is equivalent. It is correct to select any model. The main one
is to look at the model more conveniently to analyze the problem. For example, when a repairer analyzes a
circuit board component, the device under test is connected with other components on the board. The
component model may be changed. The capacitance and resistance in the actual circuit are connected in
parallel. When the measurement is performed, the parallel model can directly know how large the
resistance of the capacitor is. The road analysis is very convenient. So you need to choose the right model
according to the actual situation.
7.6 Why is the value of Q, D, R of the measuring capacitor sometimes negative? And θ is greater than
90°?
Theoretically, there should be no negative value. When the negative value occurs, the absolute value
of Q is still very high, which means that there is a slight phase error. This is electricity. The error caused
by the limited accuracy of the bridge cannot be completely avoided. Negative values sometimes occur
because of over-zeroing, which requires careful confirmation of open and short-circuit clearing.
For a negative D value or a negative Q value, how to evaluate the true value of a component can be
done by using a relative value method, which is specifically as follows: First, measure a good quality
capacitor, record D as a reference value, and measure D of other components. Subtracting the reference
value gives a more realistic D value.
7.7 Why does the reading of the meter jump after inserting the external test lead? The
external test lead is inserted. The test lead introduces external interference. In addition, after the open
circuit is cleared, the display is >1000M // 0000P, but it is easy to change. The reason for the change is
that the relative attitude of the test line is changing. Although the test line is not moving, the bridge is very
