Thursday, November 26, 2015

Simple and Accurate LC Meter Circuit - 16F690


Simple and Accurate LC Meter - 16F690
Digital LC Meter

A LCR meter [Inductance (L), Capacitance (C), and Resistance (R)] is a piece of electronic test equipment used to measure the inductance, capacitance and, resistance of a component. Inductance is the property of an electrical circuit causing voltage to be generated proportional to the rate of change in current in a circuit. In Electronics, capacitance is the ability of a body to hold an electrical charge. Capacitance is also a measure of the amount of electrical energy stored (or separated) for a given electric potential. The electrical resistance of an electrical element measures its opposition to the passage of an electric current. The meter reads L, C and R directly with no human calculation required.

Recently I found this LC meter project on internet and I was looking for that kind of project. Therefore, I build. Amazing it is work! Also the accuracy of this LC meter is great and it is very easy to build. So that, I post it here, because I think it is useful to you. You can visit original post from using this link: LMC3

The data below were determined based on theoretical calculations, the scale and the display automatically change.

Min Max Resolution Accuracy
Non Polar Condenser 1pF 1nF 0.1pF 1%

1nF 100nF 1pF  1%

100nF 1uF  1nF 2.5%
Electrolytic Capacitor 100nF 100,000uF 1nF 5%
Inductor 10nH 20H 10nH 5%
Resistance 1mΩ 0.5Ω 1mΩ 5% 
Inductance 0.5Ω 30Ω 10mΩ 10%
Specifications of the LC Meter

Simple and Accurate LC Meter Circuit
LC Meter Diagram

LC Switch:
The purpose of this is, switch between inductance and capacitance mode. When you turn on the LC meter, you should set it to C mode.

Calibration Switch:
You can calibrate LC meter by pressing this. See Calibration for more details.

LC Meter Calibration

You have 3 modes to calibrate. When the process is completed, calibrated values are saving to the microcontroller’s internal EEPROM, so of course they are available after the re-start.

C Calibration
  1. Switch on
  2. Switch L/C switch to C position
  3. Leave the test probes freely. Do not even touch it
  4. Press and hold the CALIB button until the message Switch to meas. Then release the button
  5. Wait for the appearance of 0.00 pF
L Calibration
  1. Switch on
  2. Switch to the L position
  3. Connect L/C probe and GND probe together
  4. Press and hold the CALIB button until the message Switch to meas. Then release the button
  5. Wait for the appearance of 0.00 uH
ESR Calibration
  1. Switch on
  2. Switch to the C position
  3. Connect LE probe and GND probe together
  4. Press and hold the CALIB button until the message Switch to meas. Then release the button
  5. Note the value shown on the screen
Calibration Values
  • F0 = 499.9k
  • Fcal = 355.9k
  • Re = 180Ω
  • Uesr0 = 58.3mV
  • Fesr = 83.6k
  • Rx = 0mΩ [-5mΩ to 5mΩ]

Critical Components

All the below resistors are 1%.
(In my circuit, I used normal resistors and those are measured using digital multimeter)

  • 47Ω - R11
  • 47kΩ - R8
  • 100kΩ - R3-R5
  • 1nF - C8, C11 (Polypropylene or Polyester)
  • 33nF - C10 (Polypropylene 275V AC)
  • 10uF - C7, C9 (Tantalum)
  • 100uH - L1 (Low-loss DC resistance of 0.3-0.4Ω)


Simple and Accurate LC Meter Circuit - 16F690 test c
check 22pF ceramic capacitor

Simple and Accurate LC Meter Circuit - 16F690 test e
check 100uF electrolytic capacitor

Simple and Accurate LC Meter Circuit - 16F690 test l
check 100uH inductor

I was unable to find a reed relay, so I put 5v ordinary relay temporarily. In addition, my PCB designed for the TL2285 switches. But, I bought TL2230 by mistake :)

If the back-light brightness is low, you can increase back-light brightness by decreasing the value of the resistor R2 to 470Ω - 1k. You can change display contrast by adjusting 10k preset.
For PCB, Schematic and hex file, click download button.

You must discharged capacitors properly before measuring.

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  1. Thanks for sharing this very informative post! This is so interesting to know. I really love reading your stuff being posted here.Anchor switches price | Electrical switches online

  2. how many capacitor value mesuring this project..

  3. other ic use this circuit?what is the same ic this project?

    1. Only single Ic is use for this circuit and its very cheap. its cost about LKR 200.00

  4. why this circuit using relay....
    my circuit not mesuring non polar capacior...

    1. This is not my project. Please find the original post from here.

  5. Great blog! I really love how it is easy on my eyes and the information are well written. I am wondering how I might be notified whenever a new post has been made.
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  6. assemble the entire project but when I light it up does not show anything the display

    1. Check whether relay work or not when connected to the power. if you hear sound from relay then check display connection. Also check MCLR pin

  7. Thank you for the answer, I hear that the relay is triggered when I connect the energy use this model N4078-05-50 5V - 50W - 50Ohm. Can i remove the relay to test if truly i turn on doing a jumper?

    1. If the relay triggered when power applied to the circuit, then check your LCD. and also make sure the chip was correctly programmed.

  8. Hello scorpionz I cannot make a pledge the LC, you said that verify the MCLR but not as doing so, apology for my stupid questions but I started at the Electronica makes my little time and there are still things that are not. The pin positive relay i always have 0v



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