The LCR table is a very useful device for measuring three basic impedance elements, namely inductance (L), capacitance (C), and resistance (R). Recently, I won the TENMA 72-8155 Digital LCR meter from Newark (NEWARK) for review. I am very happy to receive it because there is no dedicated LCR table in my home laboratory. This is my fast comment on the product.
TENMA 72-8155 Digital LCR Table
Brief Overview of TENMA 72-8155 LCR Measuring Instrument
Tenma 72-8155 is a moderate handheld digital multimeter for measuring impedance parameters. It can measure capacitance, inductance, resistance, and transistor H FE in a reasonable precision (listed later). The instrument can also test diodes and conduction through buzzers. This portable instrument is designed with a fashionable body, using a 9V alkaline battery (included in the packaging) and displays the value of the measurement parameters on the 3-bit and 1/2-bit LCD display. The physical dimensions of the instrument are 6.77 inches (h) x 3.27 inches (W) x 1.50 inches (D).
the first thing
The measurement range is manually selected by rotating switch, as in a typical digital multimeter. The table below shows the LCR measurement range and the corresponding expected accuracy, such as the manufacturer's data sheet.
Resistance measurement range
LC measurement range
Note: High voltage capacitors must discharge before testing
The selection between L and C measurements is performed by a button located in the upper right corner of the chair interface. The figure below shows the detailed view of the meter and describes the structure of the meter.
Electric meter structure
Let us do some actual measurements now. When measuring parameters, always select the appropriate range to increase resolution and accuracy. For example, if the capacitance value between 2 to 20 NF is to be measured, the range of 20 NF can provide optimum accuracy. I measured some capacitors and inductors of random values, and found that the instrument reading is very consistent with their rated values (see the figure below).
Measuring capacitor (left one rated value is 0.1 Uf, the right one is 100 Uf)
100 UH rated inductance
"One of the best uses of the instrument is to find the inductance of the coil. Inductor coils are widely used in oscillators and RF circuits. Understanding the inductance of the coil can simplify the design and debugging of the oscillator circuit.
Measuring the inductance of the coil
The minimum range of resistance measurement is 200? . Although this range can measure the resistance between 0 and 200 Ω, it should be taken particularly to accurately measure low resistance. For example, the picture below shows 0.22? Resistance. The output is shown to be 0.4Ω, which is almost twice the actual value. Additional resistors come from the measurement wire. If you shorten the two leads, the instrument will display 0.2? . In the case where the short-circuit resistance is 0F, the short-circuit resistance must be subtracted from the meter reading to obtain an accurate measurement result.
When measuring the low resistance value, consider the input terminal resistance
The meter can also measure the transistor H fE. The figure below shows the HFE reading of the BC557C PNP transistor. The reading display 490 is very energetic with the value described in the BC557C data sheet.
Measure the HFE of the BC557C PNP transistor
Editor in charge: WV, read full text
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