home » Hairstyles » LC Meter A device for measuring capacitance and inductance on PIC16F628A. Digital LC Meter Tester for Measuring Inductance Capacitance and Frequency

LC Meter A device for measuring capacitance and inductance on PIC16F628A. Digital LC Meter Tester for Measuring Inductance Capacitance and Frequency

The E7-22 device (unit 533) is designed to measure the parameters of electrical circuit elements: electrical resistance, inductance and capacitance.

The appearance of the front panel of the E7-22 device is shown in Fig. 1.4.1.

A detailed description of the procedure for working with the device and calculating the error of the measurement result is given in the operating manual “Digital immittance meter E7-22”, included in the package of the device. Below are just the basic information needed to take measurements.

Turning on the device. Connect the 224.1 power supply to the connector on the top side of the E7-22 device housing. Connect the power supply plug to a free socket of a single-phase power supply (218). If the device does not turn on, briefly press the upper left button on the front panel of the device - . The electrical connection diagram is shown in Fig. 1.4.2. As an example, the figure shows the connection of a capacitor when measuring capacitance.

Rice. 1.4.2. Electrical connection diagram for measuring parameters
elements of electrical circuits using the E7-22 device.

Basic controls of the device.

1. The “Frequency” button sets the frequency at which measurements will be performed. Successive presses of the button switch the frequency between 120 Hz and 1 kHz. The selected value is shown on the display.

2. The “PAR/SEQUENTIAL” button selects the equivalent circuit of the element: parallel (PAR) or serial (SER). The corresponding indicator switches on the display.

3. “Range” button is used to fix the measurement range. When you turn on the device, the automatic selection of the measurement limit mode is set (“Auto” on the indicator). Briefly pressing the button switches the measurement limit. Pressing and holding the button for more than 2 s returns the automatic limit selection mode.

4. The “L/C/R” button switches the main measured parameter of the element: inductance, capacitance or resistance.

5. The “Q/D/R” button sequentially switches the auxiliary measured parameter: Q – quality factor, D – loss tangent, R – resistance. The indicator displays only those auxiliary parameters that are compatible with the selected main parameter.

6. “Hold” button. A short press of this button blocks the update of the measurement result on the indicator; a second short press removes the lock. In blocking mode, the indicator displays the “H” symbol. Pressing and holding this button for more than 2 s turns on (or turns off) the indicator backlight.

7. “MIN/MAX” button - turns on the extreme value recording mode. Successive short presses cycle through the various options available in this mode. To exit the mode, this button must be pressed and held for more than 2 s.

8. “Set” button – sets the program settings of the device (not discussed here).

9. “Δ” (“Relative”) button – sets the relative measurement mode. To disable the mode, you must press the button and hold it for more than 2 s.

10. “HI/LO Limit” button – switches on the upper and lower limits for tolerance control.

11. “TOL” button – button to turn on the relative deviation measurement mode.

Taking measurements.

1. If the device is turned on, turn off and turn on the power again. Some settings will be reset to their original state.

2. Select:

Type of measured parameter (button “L/C/R”);

Auxiliary measured parameter (button “Q/D/R”);

Element equivalent circuit ("PAR/SEQUENTIAL" button);

Measurement frequency (button “FREQ”).

3. Measure the element parameters.

It is not permissible to supply voltage to the input of the device! Before measurement, capacitors must be discharged by short-circuiting their terminals.

Connect the element to the input of the device and measure its parameters. Polar capacitors must be connected in accordance with the polarity of the device input sockets.

Single-phase power supply G1 is designed to safely power the RLC Meter (533) unit.

Multimeter

The multimeter is designed to measure voltages, currents, resistances, temperatures, as well as to test diodes and transistors. Its general view is shown in Fig. 1.5.1. Detailed technical information about multimeters and operating instructions are provided in the manufacturer's operating instructions. Here we provide only basic information.

To turn on the multimeter, you must press the “ON/OFF” button located on the left under the indicator.

At the top of the multimeter there is a reading device - a digital indicator. Below is a mechanical switch for operating modes and measurement limits of the devices. Under the switch there are sockets for connecting conductors:

“COM” socket is a common socket for connecting the device for any measurements. When measuring direct voltage or current, the socket corresponds to the “-” (minus) of the device. When measuring resistance, “-” (minus) is supplied to the “COM” socket from an internal source. The polarity of internal sources must be taken into account, for example, when testing diodes;

The “VΩ” jack is used to connect a second conductor to the device at the voltage and resistance measurement limits. When measuring direct voltages and currents, this socket corresponds to the “+” of the device. When measuring resistance, this is the “+” socket of the internal source.

The “A” socket of the MY60 multimeter is intended for connecting a current measurement circuit at all current measurement limits except 10 A. The socket corresponds to the “+” of the device.

The “10 A” socket is intended for connecting a current measurement circuit at a limit of 10 A. The socket corresponds to the “+” of the device.

When measuring direct voltage, the device readings are positive if the voltage is directed from the “V” socket (i.e., “+”) to the “COM” socket (i.e., “-”). Likewise, current is considered positive if it flows through the device in the direction from the “+” socket (i.e. “mA”, “A” or “10A”) to the “-” socket (“COM”).

A pair of TEMP sockets is intended for connecting a thermocouple included in the device or a special cable, connecting these sockets with a thermocouple mounted inside a miniblock (for miniblocks, see below).

Sequence of working with a multimeter:

1. In the initial state, the device is disconnected from the circuit being measured.

2. Set the type of measured value and the required measurement limit using the switch. If the value of the measured voltage or current is not known in advance, it is necessary to set the maximum limit for measuring the corresponding value, which prevents the device from failure when power is supplied to the circuit under test. It is possible to supply voltage (current) to the inputs of multimeters only if their switches are set to the voltage or current measurement positions.

3. Connect the device to a de-energized circuit under test. Turn on the power supplies of the multimeter and the circuit under test and take measurements.

It is allowed to switch to a smaller measurement limit of the measured value: the limit switch is moved to the position adjacent to the original one.

When switching a limit, it is unacceptable, even for a short time, to set the switch to positions corresponding to other measured values.

5. To switch the device to another section of the circuit under test, you must turn off the power to the circuit, change the connection of the multimeter, set the measurement limit, and reapply power to the circuit under test.

6. When measuring the parameters of elements of electrical circuits: diodes, resistors, capacitors, it is unacceptable to apply voltage from external sources to the input of the device (it is unacceptable to measure the parameters of elements in a circuit under voltage). Before measuring capacitance, the capacitor must be discharged by short-circuiting its terminals.

To ensure reliable long-term operation of the multimeter, follow these rules:

· When the order of the measured quantity is unknown, set the measurement limit switch to the largest value.

· When switching a limit, it is unacceptable, even for a short time, to set the switch to positions corresponding to other measured values.

· Before turning the switch to change the type of work (not to change the measurement limit!), disconnect the probes from the circuit being tested.

· Do not measure resistance in a circuit that is energized.

Electric heater block

The electric heater block (Fig. 1.6.1) is used to determine the temperature coefficient of resistance of various materials. The block allows you to set and automatically maintain the heater temperature. The unit contains a low-power +5 V source, used as an additional power source in some experiments.

To the left of indicators 3 and 4 (Fig. 1.6.1) there are 4 LEDs installed on the front panel of the temperature controller

K1 – switched on during heating;

K2 – not used;

AL – indicator of exceeding limit values (not used).

RS – automatic control mode indicator. Must be turned on for normal operation of the unit in automatic control mode. When automatic control is turned off (see below), the device works only as an indicator of the heater temperature.

Setting the temperature of the electric heater.

1. Press one of the control buttons 5 or 6 of temperature regulator 2 (Fig. 1.6.1).

The heater temperature set point indicator starts blinking
(SV, green indicator 4).

2. To change the set temperature value, press buttons 5 (decrease) or 6 (increase temperature) again. Holding the button for some time turns on the automatic rapid value change mode. The indicator continues to flash during installation.

3. After setting the required temperature value, you must press button 7 once (Fig. 1.6.1). Indicator 4 stops blinking. The temperature is set.

Rice. 1.6.1. Front panel of the electric heater unit (394.2).

1 – heater hole; 2 – temperature meter-regulator; 3 – indicator of the current value of the heater temperature (PV); 4 – indicator of the heater temperature set value (SV); 5,6,7 – temperature controller control buttons; 8 – power switch; 9 – +5 V power supply sockets.

This accurate LC meter is built with inexpensive components that are very easy to find in radio stores. The range of the LC meter is quite wide and is suitable for measuring even very low values of capacitance and inductance.

Printed circuit board - drawing

Inductances - measurement ranges:

10nH - 1000nH
1uH - 1000uH
1mH - 100mH

Capacitance measurement ranges:

0.1pF - 1000pF
1nF - 900nF

A big advantage of the device is automatic calibration when the power is turned on, which eliminates errors in calibration, which is inherent in some similar inductometer circuits, especially analog ones. If necessary, you can recalibrate at any time by pressing the reset button. In general, this LC meter is fully automatic. MK firmware PIC16F628 .

Device components

Over-precision components are optional, with the exception of one (or more) capacitors, which are used to calibrate the meter. The two 1000 pF capacitors at the input should be of fairly good quality. Expanded polystyrene is more preferable. Avoid ceramic capacitors, as some can have high losses.

Two 10 µF capacitors in the generator should be tantalum (they have low series ESR resistance and inductance). A 4 MHz crystal should be strictly 4.000 MHz, and not something close to this value. Every 1% error in the crystal frequency adds 2% errors when measuring the inductance value. The relay should provide approximately 30 mA of tripping current. Resistor R5 sets the contrast of the LCD display of the LC meter. The device is powered by a regular Krona battery, since the voltage is further stabilized by the microcircuit 7805 .

This project is a simple LC meter based on the popular cheap PIC16F682A microcontroller. It is similar to another one recently published here. Typically, such features are difficult to find in low-cost commercial digital multimeters. And if some can still measure capacitance, then inductance definitely cannot. This means you will have to assemble such a device with your own hands, especially since there is nothing complicated in the circuit. It uses a PIC controller and all the necessary board files and HEX files for programming the microcontroller are available at the link.

Here is the circuit diagram of the LC meter

Choke at 82uH. Total consumption (with backlight) 30 mA. Resistor R11 limits the backlight and must be sized according to the actual current consumption of the LCD module.

The meter requires a 9V battery. Therefore, a 78L05 voltage stabilizer is used here. An automatic sleep mode for the circuit has also been added. The time in operating mode corresponds to the value of capacitor C10 at 680nF. This time in this case is 10 minutes. MOSFET Q2 can be replaced with BS170.

During the setup process, the next goal was to keep the current consumption as low as possible. By increasing the value of R11 to 1.2 kΩ, which controls the backlight, the total device current was reduced to 12 mA. It was possible to reduce it even more, but visibility suffers greatly.

The result of the assembled device

These photos show the LC meter in action. On the first there is a 1nF/1% capacitor, and on the second there is a 22uH/10% inductor. The device is very sensitive - when we install the probes, there is already 3-5 pF on the display, but this is eliminated when calibrating with a button. Of course, you can buy a ready-made meter with similar functions, but its design is so simple that it’s not at all a problem to solder it yourself.

Discuss the article LC METER

I somehow made myself this extremely useful and irreplaceable device, due to the urgent need to measure capacitance and inductance. It has surprisingly very good measurement accuracy and the circuit is quite simple, the basic component of which is the PIC16F628A microcontroller.

Scheme:

As you can see, the main components of the circuit are PIC16F628A, a character-synthesizing display (3 types of display 16x01 16x02 08x02 can be used), a linear stabilizer LM7805, a 4 MHz quartz resonator, a 5V relay in a DIP package, a two-section switch (for switching measurement modes L or C ).

Firmware for microcontroller:

Printed circuit board:

PCB file in sprint layout format:

The original board is wired for a relay in a DIP package.

I didn’t have such a thing and I used what I had, an old compact relay that was just the right size. I used tantalum scoop capacitors as tantalum capacitors. The measurement mode switch, power switch and calibration button were used, once removed from old Soviet oscilloscopes.

Test leads:

Should be as short as possible.

During assembly and setup, I followed these instructions:

Assemble the board, install 7 jumpers. First install jumpers under the PIC and under the relay and two jumpers next to the pins for the display.

Use tantalum capacitors (in the generator) - 2 pcs.
10uF.
The two 1000pF capacitors should be polyester or better (approx. tolerance no more than 1%).

It is recommended to use a backlit display (note that the limiting resistor 50-100 Ohm is not indicated on the diagram, pins 15, 16).
Install the board into the case. The connection between the board and the display can be soldered at your request, or made using a connector. Make the wires around the L/C switch as short and rigid as possible (to reduce interference and to properly compensate for measurements, especially for the grounded end L).

Quartz should be used at 4.000MHz, 4.1, 4.3, etc. cannot be used.

Testing and calibration:

Check the installation of parts on the board.
Check the settings of all jumpers on the board.
Check that the PIC, diodes and 7805 are installed correctly.
Don’t forget to flash the PIC before installing it in the LC meter.
Turn on the power carefully. If possible, use a regulated power supply for the first time. Measure current as voltage increases. The current should be no more than 20mA. The sample consumed a current of 8mA. If nothing is visible on the display, turn the variable contrast adjustment resistor. The display should read " Calibrating", then C=0.0pF (or C= +/- 10pF).
Wait a few minutes (“warm-up”), then press the “zero” (Reset) button to recalibrate. The display should read C=0.0pF.
Connect the "calibration" capacitor. On the LC meter display you will see the readings (with +/- 10% error).
To increase the capacitance readings, close jumper “4”, see the picture below (approx. 7 PIC leg). To decrease the capacitance readings, close jumper “3” (approx. 6 PIC leg) see the picture below. When the capacitance value matches the “calibration” value, remove the jumper. The PIC will remember the calibration. You can repeat the calibration many times (up to 10,000,000).
If there are problems with measurements, you can use jumpers “1” and “2” to check the frequency of the generator. Connect jumper “2” (approx. 8 PIC pin) and check the frequency “F1” of the generator. Should be 00050000 +/- 10%. If the readings are too high (near 00065535), the device goes into “overflow” mode and displays the “overflow” error. If the reading is too low (below 00040000), you will lose measurement accuracy. Connect jumper "1" (approx. 9 PIC pin) to check frequency calibration "F2". It should be about 71% +/- 5% of “F1” which you got by connecting jumper “2”.
To get the most accurate readings, you can adjust L until you get F1 around 00060000. It is preferable to set “L” = 82 µH on a 100 µH circuit (you may not buy 82 µH;)).
If the display shows 00000000 for F1 or F2, check the wiring near the L/C switch - this means the generator is not running.
The inductance calibration function is automatically calibrated when capacitance calibration occurs. (approx. calibration occurs at the moment the relay is activated when L and C in the device are closed).

Testjumpers

F2 check
F1 check
Decrease C
Increase C

How to take measurements:

Capacitance measurement mode:

Move the measurement mode selection switch to position “C”
Press the “Zero” button
The message “Setting! .tunngu." wait until “C = 0.00pF” appears

Inductance measurement mode:

Turn on the device and wait until it boots
Move the measurement mode selection switch to the “L” position
We close the measuring wires
Press the “Zero” button
The message “Setting! .tunngu." wait until “L = 0.00uH” appears

Well, that’s it, leave your questions and comments in the comments under the article.

There are many circuits on the Internet for making an LC meter at home (a device for measuring the capacitance of capacitors and the inductance of coils). Also, in almost any electronics store you can buy a ready-made meter. But, the first option requires at least the skill and ability to flash a microcontroller, and the second option requires 50 or more extra dollars in your wallet. In my city it turned out to be problematic to buy a ready-made LC meter. But I was lucky, I downloaded an archive with the Zmeter program and description from the vrtp.ru forum.

Using a couple of resistors and a program, you can assemble a PC-based complex resistance meter in an hour, and the program quite accurately shows the ESR of electrolytic capacitors. In my opinion, this is a necessary thing, and if you compare it with the resources expended, I can say that I have not yet seen a better LC meter circuit than this one. It can be assembled in an hour with etching of the board, configured in a couple of minutes, and there are practically no costs for components. All details of assembling and configuring the program are in the archive. It worked for me right away. 16 ohm ballast resistor, 46 ohm reference resistor, Audigy SE sound card, audio cable and two TRS plugs.
Below are photos and screenshots of measurements.
Device assembled