This video describes an easy to build ESR meter and compares it to more modern digital devices. It is based on a construction article from a 2001 electronics magazine.
many years ago when I was a Tech we used to replace all suspicious caps up front, particularly the well known dodgy ones ( Low value and tantalum). This was quicker and cheaper than testing each one individually and possibly having something intermittent and marginal slip by.
The diodes D1 and D2 can be considered fly-back diodes, or clamping diodes. If the capacitor is charged, it will force current flow back through the capacitor, rather than applying it to the differential amplifier.
Can anyone tell me where i can find the components template used in rhis schematic ? I mean the graphics representing the electronic components. What is the name of this style of schematic.
I have seen many of these spilt power supplies from guitar pedals, but this one is weird. the output of the opamp is connected to GND ... also the switch from the 9 volt batteries is connected to 4.5V. So you set GND for the whole circuit at 4.5V, but where is actual ground or -4.5V?
This is a common way to do it. You use an opamp with the non-inverting input connected to a voltage divider to set it to half the supply voltage. The output of this opamp is now the "gnd" connection. This is only really useful for IC1-c, which is an inverting amplifier with the virtual ground point at pin 9. The other opamp parts don't need a reference to ground as one is an oscillator and the other is a rectifier.
If you were to use non-inverting opamp stages, each would have it's own voltage divider on the non-inverting pin. However, this does increase noise as opposed to using a bipolar supply.
The output of that rail splitter is not shorted to the negative terminal of the battery. It's defining a halfway voltage which we're choosing to call 'ground' and label as such.
I wonder why is there two branches of dividers R9,R10 and R11,R12 and a (pseudo) differential amplifier? Why not just one branch and a non-inverting amplifier? (I know that the direction on the ammeter would be different.)
Hi odieadog, In this case the meter needed to determine whether the cap was good ( LED off ), or shorted ( LED on ), since the meter would indicate full scale ( zero ohms ) in both cases. This configuration allowed the bridge and IC1-c to differentiate between an AC short ( normal good capacitor ) , and a DC short ( bad shorted capacitor ) . If you scope pin 8 of IC1-c , the 100 Khz signal is clamped up about 2 volts dc when the probes are shorted. This is enough to bias the base of Q3 into conduction illuminating the LED. The reactance of C6 at 100 Khz is 1.6 ohms. Therefor the AC the level at the base of Q3 is only 1/9375 the level at pin 8 and Q3 remains off during normal measurements. There are obviously other ways to accomplish the same function and the author of this article made us of all four op amps on this IC. Thanks for watching and the great comment.
"Across", there's no such word as "acrost". Subbed though 😀The TL081 is a single opamp, you most definitely mean the TL084, or TL074 which are quads. No idea what an "asamal multivibrator" is, I think you mean "os-stable", astable.
Super excellent! You posted the schematic and went through it completely. That makes for good communication and teaching. I am so grateful. Thanks!
many years ago when I was a Tech we used to replace all suspicious caps up front, particularly the well known dodgy ones ( Low value and tantalum). This was quicker and cheaper than testing each one individually and possibly having something intermittent and marginal slip by.
Very good
Thanks for posting
The diodes D1 and D2 can be considered fly-back diodes, or clamping diodes. If the capacitor is charged, it will force current flow back through the capacitor, rather than applying it to the differential amplifier.
Thanks 👍
Can anyone tell me where i can find the components template used in rhis schematic ? I mean the graphics representing the electronic components. What is the name of this style of schematic.
That schematic also looks like it came from Silicon Chip Australia.
I have seen many of these spilt power supplies from guitar pedals, but this one is weird.
the output of the opamp is connected to GND ... also the switch from the 9 volt batteries is connected to 4.5V.
So you set GND for the whole circuit at 4.5V, but where is actual ground or -4.5V?
This is a common way to do it. You use an opamp with the non-inverting input connected to a voltage divider to set it to half the supply voltage. The output of this opamp is now the "gnd" connection. This is only really useful for IC1-c, which is an inverting amplifier with the virtual ground point at pin 9. The other opamp parts don't need a reference to ground as one is an oscillator and the other is a rectifier.
If you were to use non-inverting opamp stages, each would have it's own voltage divider on the non-inverting pin. However, this does increase noise as opposed to using a bipolar supply.
The output of that rail splitter is not shorted to the negative terminal of the battery. It's defining a halfway voltage which we're choosing to call 'ground' and label as such.
I wonder why is there two branches of dividers R9,R10 and R11,R12 and a (pseudo) differential amplifier? Why not just one branch and a non-inverting amplifier? (I know that the direction on the ammeter would be different.)
Hi odieadog, In this case the meter needed to determine whether the cap was good ( LED off ), or shorted ( LED on ), since the meter would indicate full scale ( zero ohms ) in both cases. This configuration allowed the bridge and IC1-c to differentiate between an AC short ( normal good capacitor ) , and a DC short ( bad shorted capacitor ) . If you scope pin 8 of IC1-c , the 100 Khz signal is clamped up about 2 volts dc when the probes are shorted. This is enough to bias the base of Q3 into conduction illuminating the LED. The reactance of C6 at 100 Khz is 1.6 ohms. Therefor the AC the level at the base of Q3 is only 1/9375 the level at pin 8 and Q3 remains off during normal measurements. There are obviously other ways to accomplish the same function and the author of this article made us of all four op amps on this IC. Thanks for watching and the great comment.
What was the error in the schematic if you were showing it?
Hi ivolol, The schematic in my video is the correct one. The original article had R11 connected to R13 instead of the collector of Q2.
"Across", there's no such word as "acrost". Subbed though 😀The TL081 is a single opamp, you most definitely mean the TL084, or TL074 which are quads. No idea what an "asamal multivibrator" is, I think you mean "os-stable", astable.
My "t" needed a little more volume
Freudian slip. 😅