ELEKTOR FORUMS

Hello, me and noticed in this project that the switch S2 interrupts the feeding of the circuit, but not of IC7 to that this is owed?

Richard USA

Very Thank you Jan.
1) do you tell me it is necessary to use the PIC 16F877A-20P? or does it also work with the PIC 16F877A-IP?. am I using the 16F877A-IP there is some problem?
2) which is the maximum value in Homs that can measure the instrument?, is it outstanding that it measures values of 50Homs or 75 Homs?
3) it is unstable the adjustment of the Offset in the pin 7 of the LF412, for moments intersect and it oscillates between 38 and 44 mv. to that this is?

Richard USA

Hi Mehamed!

Please read my comments to "sonytel" which I copy here:

You're right about the +bat to LF412. There's a PCB error. It's easy to correct and the error doesn't influence the performance it does drain the battery though, so it should be corrected. Cut the track to LF412 and connect pin 8 to the switched side of S2, the on/off switch!

Regarding the offset of LF412, you shouldn't worry too much about the exact value, it's ok if it's +30mV to +50mV. The software will make the right subtraction.

If you compare the old ESR meter with the new one, you will observe that they may differ somewhat in the ESR value.In the lower ESR values it won't be much, in fact negligible, (and this is what is important) If you measure an ESR of 50 Ohms or more you shouldn't care if the correct value was 60 Ohms or 40 Ohms, you should exchange it! It is unavoidable because the new ESR meter automatically shifts from ESR to DC mode, the build up of DC charge is hard to remove on larger value caps. This function was regarded so convienent that we had to implement it. To remedy some of these problems, please exchange R5,R6,R7,R8 with the nearest 1% types. And replace R30/180 Ohm with a 1KOhm. On large caps you have to let the meter perform several measurements until the reading is stable.

Flemming J.

Capacitor ESR Tester 'The good, the bad and the leaky… ' by Flemming Jensen

Hi, regarding the above project I have built and calibrated the circuit, I have followed the set up instructions in the manual, and everything seems to check out fine, however the instructions are a little scant in interpreting the display results regarding ESR values, I have a start up reading of 20, when I put the test probes accross a known good capacitor(2200uf 200v) , I get a reading of 10, what does this mean? There is also a switched part of the circuit working as an ohms meter that also does not appear to function the way it should. Could I also add that in the parts list C3,C4 and C5 are tantalum type capacitors, I have used Electrolitic, is it imperative that they are tantalum? Also the display itself is a direct RS components replacement rather than the Varitronix device in the listing, could that also be a factor? But please bear in mind the display worked faultlesly during the set up procedures.
> Many Thanks in advance for your help
> Yours Roy Bloor UK
My appologies if this is not the right place to post a question