ESR meter with extended scale. - Page 1
Forum section: electronics / projects

author: iet
author_rank: Frequent Contributor
timestamp: April 24, 2024, 04:04:18 pm
content: Basic information here.https://electronicsdesignfun.blogspot.com/p/esr-meter.htmlThe meter is adapted to the tester body.The front panel contains a zero regulator, a power switch, and a graduated scale. The calibration was done using SMD resistors with low inductance.Scale: 0.005-5 Ohm.Some changes have been made to the original scheme.U1-LM833Resistors:R4-5.6k,R5,R6-0.1,R8-20k,R11-100kD1,D2-1N5817The transformer is wound on a ferrite ringSupply voltage:9vFrequency:100 kHzVpp:100mV

author: enut11
author_rank: Super Contributor
timestamp: April 25, 2024, 10:16:31 pm
content: Interesting adaption for an old analog multimeter. How does the scaling work?

author: iet
author_rank: Frequent Contributor
timestamp: April 26, 2024, 02:34:34 pm
content: Quote from: enut11 on April 25, 2024, 10:16:31 pmThe values on the ohms scale of the multimeter are indicated in red.The ESR values in mohms are indicated in blue.

author: iet
author_rank: Frequent Contributor
timestamp: April 27, 2024, 05:41:47 pm
content: As you know, the ESR of a capacitor can react to the heat of your hands. And the result may not correspond to the actual value. In addition, to obtain the most reliable result, very reliable contact between the probes and the legs of the capacitor is necessary.Therefore, a simple device was made to install and measure the ESR of capacitors.

author: iet
author_rank: Frequent Contributor
timestamp: May 07, 2024, 09:59:35 am
content: I made a small modification to the ESR meter.I used larger cross-section wires. I used elements with greater temperature stability in the 100 kHz generator circuit. Previously, the generator frequency drifted to 100-200 Hz during several hours of operation. Now the frequency is stable at 100 kHz.

author: enut11
author_rank: Super Contributor
timestamp: May 08, 2024, 07:20:38 am
content: @iet. Thanks for the update. It will be one of my future projects when I get the time. Thanks for sharing.enut11

author: iet
author_rank: Frequent Contributor
timestamp: May 08, 2024, 05:04:45 pm
content: Always positive to help in any way I can.I would like to say a little more about the components used.There are no special requirements for resistors and capacitors, except for the generator circuit. More stringent requirements for diodes and especially for the operational amplifier.The best Schottky diodes are the 1N58 series..., but there may be others.The stretch and linearity of the scale depend to some extent on them.The most requirements are for the operational amplifier. It must be LM833 or similar in characteristics. I advise you to pay attention to the frequency range that is indicated in the datasheet.It is optimal when it is 8-16 MHz. The slew rate is of secondary importance.It should also be noted that the actual characteristics of the op amp from different manufacturers may differ slightly.Additionally, different op amps have different maximum gain values depending on the supply voltage.As for microammeters, everything is very simple. The more sensitive it is, the better.

author: iet
author_rank: Frequent Contributor
timestamp: May 09, 2024, 12:30:09 pm
content: Probes.The main requirement for them is minimal resistance and good contact.The best solution would be a wire cross-section of 2x2.5 mm. An audio wire is perfect here. There is no need to separate the wires, this reduces interference. A length of 40 cm is optimal.Solder the probes directly to the transformer.

author: iet
author_rank: Frequent Contributor
timestamp: May 13, 2024, 04:28:29 pm
content: Anyone who doesn’t like a multimeter with long probes can make an ESR meter in the form of tweezers. The prototype was the MS8911 tweezers, I used spare tips from it. At the bottom I attached a socket for a 9V battery.The microammeter can be installed in any convenient place.

author: iet
author_rank: Frequent Contributor
timestamp: May 14, 2024, 07:09:26 am
content: Measuring ESR of capacitors.

author: iet
author_rank: Frequent Contributor
timestamp: May 17, 2024, 04:47:06 pm
content: I redid the power supply for the tweezers. Instead of a socket and a 9V battery, I made a homemade socket for two CR2450 batteries. Now the supply voltage is 6V. Everything works well due to the high gain of the op-amp.The tweezers have become somewhat lighter and more convenient.A 1mA milliammeter is attached to a small movable stand. It can be installed in any suitable place on the table and you can choose any angle of inclination.

author: iet
author_rank: Frequent Contributor
timestamp: May 17, 2024, 08:20:37 pm
content: In this design, the scale is quite stretched near zero and slightly compressed to 1 Ohm. At the same time, good linearity is maintained.Here are some ESR measurements of capacitors.

author: iet
author_rank: Frequent Contributor
timestamp: May 19, 2024, 01:44:25 pm
content: Now we can measure SMD calibration resistors with low inductance with tweezers.We make sure that there is no need to draw a new scale.

author: iet
author_rank: Frequent Contributor
timestamp: May 20, 2024, 01:28:26 pm
content: Once the design was complete, it was time to evaluate the effect of the inductance of the resistors on the calibration of the ESR meter scale.Three resistors with the same resistance of 100 mOhm were studied.With increasing inductance, the deviation from the actual value on the scale increased.

author: iet
author_rank: Frequent Contributor
timestamp: May 21, 2024, 04:03:10 pm
content: So the moment came when I decided to measure a very low ESR. I had to buy capacitors from Panasonic-Conductive Polymer Aluminum Electrolytic Capacitors. SP-Cap GY 820 uF, 2v.These capacitors have a max. ESR of 3mOhm.The measurement gave a result of approximately 2 mOhm, which in principle coincides with the data from the datasheet.https://api.pim.na.industrial.panasonic.com/file_stream/main/fileversion/8713

author: AlienRelics
author_rank: Unknown
timestamp: May 22, 2024, 09:20:20 pm
content: Nicely done.

author: enut11
author_rank: Super Contributor
timestamp: May 23, 2024, 05:33:18 am
content: Well done@iet. May have to bring this project forward.😀

author: iet
author_rank: Frequent Contributor
timestamp: May 23, 2024, 06:05:38 pm
content: Thank you everyone for your words of support.I will try to add important things and develop the topic naturally if I have time.Tweezers does the necessary job of estimating the ESR of used capacitors, even if there is no data in the datasheet.Several Nichicon GU, 330 uF-420 v capacitors were removed from the board. The measured ESR was approximately 185 mOhm. This is a good value for this type of capacitor.

author: iet
author_rank: Frequent Contributor
timestamp: May 24, 2024, 04:37:25 pm
content: Using the capabilities of tweezers, you can easily measure the resistance of SMD fuses.Fuse 5A, resistance 11 mOhms.https://www.bourns.com/docs/product-datasheets/sf-2410hi-t.pdf?sfvrsn=4d8a79f6_11

author: iet
author_rank: Frequent Contributor
timestamp: May 28, 2024, 11:41:27 am
content: Microammeter 100 µA. The scale is larger and more stretched, which is naturally more convenient for reading in general and for those with poor eyesight. I did the markings manually, which is fine for me.

author: iet
author_rank: Frequent Contributor
timestamp: May 30, 2024, 06:01:12 pm
content: If necessary, you can make a more accurate scale, 15,25,35 mOhms, etc.This matters when we select from a batch of new capacitors those that are closest in value. Or we select the best from used capacitors.But our goal is not super accuracy, but an extended scale for all types of capacitors (electrolytic, tantalum, solid polymer).

author: Uky
author_rank: Regular Contributor
timestamp: May 31, 2024, 06:59:31 am
content: Nice project.Just one comment. (Not that it affects the performance very much but...)U2A, a diff amp with G=10. Note that Zin differs between the two inputs.If wanting to perfect the design, an Instrument OPAmp could be considered.I am in need of an ESR meter myself so I will use this design as the starting point.

author: iet
author_rank: Frequent Contributor
timestamp: May 31, 2024, 06:51:50 pm
content: Quote from: Uky on May 31, 2024, 06:59:31 amThanks for the tip.I continue to improve my ESR meter.I received the ordered NE5532P. I received even greater gain, which made it possible to reduce the resistors in the load of the transformer by half. At the same time, the scale stretch near zero doubled. Now 5 mOhms corresponds to the 10 mOhms mark. Power supply is 6 V. Full scale is 500 mOhms.

author: Wolfgang
author_rank: Super Contributor
timestamp: May 31, 2024, 08:10:01 pm
content: Hi, I made an autoscaling ESR meter with autorange using an Arduino and an AD8307.Works fine, look here:https://electronicprojectsforfun.wordpress.com/homebrew-scpi-controllable-instruments-with-arduino-controllers/an-autorange-cap-esr-meter-with-scpi-connectivity/

author: hugo
author_rank: Regular Contributor
timestamp: May 31, 2024, 10:52:47 pm
content: Quote from: Wolfgang on May 31, 2024, 08:10:01 pmI believe you that it works fine, however where are the schematic and the arduino source code?

author: iet
author_rank: Frequent Contributor
timestamp: June 01, 2024, 02:44:11 pm
content: Quote from: Wolfgang on May 31, 2024, 08:10:01 pmHi, nice project.I finally adjusted all the operating modes of the circuit.The scale is very stretched near zero and moderately compressed near the maximum value.Scale: 0-0.08 Ohm.U1-NE5532PResistors:R4-5.1k,R5,R6-0.05,R8-20k,R11-100kD1,D2-1N5817Supply voltage:5vFrequency:100 kHzVpp:70mV

author: iet
author_rank: Frequent Contributor
timestamp: June 02, 2024, 07:34:44 am
content: An extended scale near zero has undeniable advantages over a compressed one. This part of the scale is used to measure capacitors with very low ESR. These are mainly modern series of solid polymer and tantalum capacitors.We can also use this section of the scale to measure the ESR of capacitors connected in parallel.

author: iet
author_rank: Frequent Contributor
timestamp: June 04, 2024, 07:11:51 am
content: I replaced the 100k adjusting resistor.Now it works vertically and takes up less space. The previous resistor was a little old and the zero adjustment was not as smooth as I would like. Now everything is fine.

author: iet
author_rank: Frequent Contributor
timestamp: June 05, 2024, 11:37:39 am
content: The ordered op amp OP275 arrived. It was purchased purely out of interest in comparison with other op amps in order to remove all questions and doubts. Summary.There are no advantages over the NE5532P. The performance is identical.But OP275 needs 10V power supply. The oscillogram is slightly distorted. Most likely this is due to the fact that JFET transistors are used there.In addition, it is much more expensive.The NE5532P is definitely unrivaled.Regarding TL072. With this circuit design it does not work. At a voltage of 9V, the needle deviates by only one division.

author: iet
author_rank: Frequent Contributor
timestamp: June 09, 2024, 11:47:25 am
content: Recently some missing resistor values ​​arrived and I finished calibrating the scale of the ESR meter, which uses the NE5532P op-amp.To be honest, I didn’t even expect it myself.The result was a very stretched, linear scale with a range of 1-100 mOhm.

author: iet
author_rank: Frequent Contributor
timestamp: June 10, 2024, 08:58:41 am
content: It is very important to know the ESR value of capacitors in any connection without removing them from the board. Also, searching for documentation on them does not always lead to success. Therefore, we can now trust our calibrated scale, which naturally speeds up the work.We must ensure that the capacitor is suitable for further use in our projects without removing it from the board.

author: iet
author_rank: Frequent Contributor
timestamp: June 21, 2024, 04:40:40 pm
content: In my work, sometimes it is necessary to make measurements with high accuracy, and to do it quickly and as efficiently as possible. Some things have to be done directly on the boards, without desoldering the components.Therefore, we studied the issue of purchasing a second tweezers with higher characteristics. In the end, I chose the LCR Pro1 Plus.In addition, I naturally wanted to check the measurement results with my 100 kHz tweezers. The results delighted me, which means my time was not wasted.

author: iet
author_rank: Frequent Contributor
timestamp: June 24, 2024, 03:26:28 am
content: I used digital tweezers to measure the resistance of the smd fuse and the esr of two 220 uF SP-CAP capacitors connected in parallel. Naturally, good contact is needed and this is provided by high-quality tips. I would even make the tips even more rigid, because sometimes sufficient effort is needed to obtain a reliable result.I also measured a capacitor from Panasonic SP-Cap GY 820 uF.

author: iet
author_rank: Frequent Contributor
timestamp: June 28, 2024, 12:47:25 pm
content: Made a slight upgrade to my tweezers.With the same dimensions, the new board added a connector for external power. The microswitch is half the size and is used when powered by batteries.All resistors, except the power bus, have a 1% tolerance. The 1nF capacitor was selected for the lowest losses.Resistors R5, R6 0.1 Ohms were replaced with smd ones. The freed up space can be used for ferite rings of larger diameter.

author: iet
author_rank: Frequent Contributor
timestamp: June 29, 2024, 09:29:30 am
content: The second tweezers are made a little differently. Of course, you can buy ready-made gold-plated tips, but this greatly increases the cost of the design. In the process of working with two tweezers, I decided to try to make my own tips from available materials. I experimented with different materials, but in the end I chose copper plates.The tips must be thin enough, while maintaining good rigidity and stability and have low resistance. Copper plates are perfect for these requirements. The only possible inconvenience is sometimes rubbing the surfaces with fine emery cloth. As you know, copper also comes in different qualities, so it is necessary to use plates well-known manufacturers, such as flexible multi-plate electrical busbars.Another significant difference from the first tweezers is the distance between the tips. 2 cm and 4.5 cm, respectively. This allows you to measure capacitors of different types with radial leads.In addition, having a low-impedance range, it is more convenient to look for short circuits on boards at more distant points.

author: iet
author_rank: Frequent Contributor
timestamp: July 01, 2024, 03:05:15 pm
content: I finally resolved the issue of powering the tweezers. Now it is combined. From an external power supply and from a 3.7 V lithium battery. This became possible due to a significant reduction in the resistance of the tip-transformer circuit. The amplifier works perfectly at a voltage of 3.7 V and even when the supply voltage is reduced to 3 ,3V. Thus, it became possible to use a lithium battery. There was a slight conflict here, because it was necessary to use two 3V batteries, and the amplifier did not work with 3V.In addition, purchasing a lithium battery is much more economical than periodically purchasing 3V batteries.On the board, instead of a microswitch, there is a micro-connector for connecting the battery. A charger micro-board is screwed to the side. The battery itself is attached to the bottom. I’ll see how long it will last for continuous operation.A steeper stand for the microammeter is used. It rotates around its axis and tilts to the required angle.The 50 µA microammeter AIME60005 from Welleman was ideal. With dimensions of 60x47 mm, it has excellent sensitivity.Scale 0-500mOhms.The scale was calibrated so that 30mOhms coincided with 30uA. This simplifies the rest of the calibration.The rest of the parameters are the same. Frequency is 100 kHz, test voltage is even lower - 40 mV.

author: iet
author_rank: Frequent Contributor
timestamp: July 02, 2024, 10:44:17 am
content: The maximum voltage of a fully charged lithium battery is 4.2 V. This is good. This means that the tweezers can confidently work within the voltage drop range of 4.2-3.3 V. The only inconvenience in this situation is the minimal adjustment of the R11 zero. Now we will monitor how much it will be over time reduce the voltage drop at rest and in working condition. What is the point of this? Very simple. A 400 mA lithium battery is used, taking into account the price and size.Let's see if there is a need to install a more powerful battery. Or vice versa, just 100-200 mA is enough .It will be even cheaper in price.As I already said, the distance between the tips of the tweezers is 45mm. Here is a good example of measuring a 10000 uF capacitor. Its length is 40 mm.ESR 22 mOhms.

author: iet
author_rank: Frequent Contributor
timestamp: July 05, 2024, 12:51:16 pm
content: Well, after 72 hours, the voltage of the lithium battery decreased by 1V. And at 3.2V, the tweezers no longer work. And this takes into account the fact that it was at rest most of the time.We can already draw some conclusions. With periodic use, a 400mA battery should last for 2-3 days. With intensive use, you will need a more powerful lithium battery in the range of 1000-2500 mA. Therefore, those who want to repeat this design can use these data to choose the optimal lithium battery for yourself.Several repeated measurements with the new scale.Very clear and easy to read scale.Many times measured solid polymer capacitor.Low impedance capacitor.

author: iet
author_rank: Frequent Contributor
timestamp: July 08, 2024, 02:03:56 pm
content: I installed a microswitch in the power supply circuit from the lithium battery. The energy savings of the lithium battery have increased significantly. Now you can turn off the power to the tweezers after each measurement.The changes also affected some resistors for calibrating the scale. I used resistors of smaller overall dimensions and, accordingly, lower inductance. The previous 100 mOhms resistor had an inductance of 10 nH, the new one has 5 nH. The calibration of the scale has become even more accurate.Added a new smaller resistor 10 mOhms.

author: iet
author_rank: Frequent Contributor
timestamp: July 11, 2024, 09:48:55 am
content: After the final settings and calibrations of the tweezers, I made a calibration test board from different solid polymer capacitors.I used copper wire of the appropriate thickness as pins. This method turned out to be very effective and does not require large financial costs.

author: iet
author_rank: Frequent Contributor
timestamp: July 14, 2024, 03:21:58 pm
content: Small microammeters are good. They take up little space and can be moved to any point on the table. But to get greater resolution of this meter, you need a more extended scale. I bought a large microammeter. It was easily adapted to this circuit.With this microammeter, I managed to obtain a resolution of 1 mOhm in the range of 0-60 mOhms. This is an impressive result, which once again proves the great capabilities of this circuit. I finished calibrating the scale.The value on the left is uA. The value on the right is mOhms.|0-250|5-200|10-150|15-100|20-80|25-60|30-55|35-50|40-45|45-40|50-35||55-30|60-25|65-20|70-15|75-10|80-7.5|85-5|90-2.5|100-0|

author: iet
author_rank: Frequent Contributor
timestamp: July 23, 2024, 02:20:13 pm
content: The development of the design continued. I wanted to reduce the dimensions to the possible minimum, thereby reducing the resistance of the probes. This made it possible, with a slight increase in the power supply to 4.2 V, to reduce the load resistance to 50 mOhms. This led to an even greater stretching of the scale.Now ESR 10 mOhms corresponds to 65 uA instead of 75 uA.This design took a little longer, but the calculations for stretching the scale were completely confirmed.This tweezers are powered by an external power supply.

author: iet
author_rank: Frequent Contributor
timestamp: July 25, 2024, 11:02:21 am
content: This is how tweezers work when repairing various devices and checking capacitor parameters.Sometimes, as a form of entertainment, I have to repair various computer and phone power supplies for my friends.Naturally, I always check the capacitors.In this case, the capacitors have good parameters for capacity and esr and do not require replacement.Sometimes there are cases of failure of digital tweezers from charged capacitors or residual voltage on the capacitor. Therefore, I had to buy a cheap capacitance meter with a fuse and attach simple tweezers to it.