Elektor Esr Meter Adjustment

[savetheday]

Hi everyone
Sorry for my awful english.
I need some help understanding ESR meter adjustment
i have Elektor [url=http://fly.srk.fer.hr/~wgottwe/esr.pdf]2002/9 ESR METER[/url]?

It says in there magazine
[quote]
ESR Tester adjustment
Before adjusting the instrument, be
sure that you have a regulated plus
5 V from IC5 and minus 5 V from
IC7. If you don’t, you’ll have to troubleshoot
your circuit board.
[b]1.[/b] Start with the voltmeter circuit.
P1 should be disconnected at this
point. Connect a known, accurate
voltage source of less than 200
mV to point TPA (test point A)
and adjust P5 until the LCD
shows the right value. Remove the voltage source. Connect TPA to TPB,
short the test leads together, and adjust
P2 for a ‘000.0’ reading. Remove the connection.
Reconnect P1.
[b]2.[/b] Connect a frequency counter or an oscilloscope
between TPC and GND. Adjust P4
for 200 kHz counter reading or 5 µS
period time on the oscilloscope.[/quote]


1-)With DMM i could measure IC5 and IC7 components +- 5 volts.
2-)I desoldered P1 and
3-)I set the power supply to 0.150 V and attached one of the crocodile connecter to TPA but i don't know which part the other one will be connected?And which part is GND on the circuitboard?
4-)Do we need to fallow exact adjustment part 2? Which has needed some oscilloscope and frequency counter measurments?

Thanks a lot

[pebe]

Ground is any of the many places where you can see a thick horizontal bar at the bottom of a vertical connecting line, eg. pins 3 and 6 of the ICL7660.

I am afraid you will need an oscilloscope or a frequency counter to carry out the calibration if you want the meter to read accurately

[savetheday]

I bought old functiongenerater and 30Mhz 2 Canaloscilloscope does it do that job?
Thanks.

[pebe]

A 30MHz scope is OK to measure a 5us period, provided the 'X' sweep is calibrated or if you can calibrate it with the function generator.

[savetheday]

I'm geting this figure.How do we set 200 kHz?There is only time/div and volts/div ?
Thanks
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[pebe]

You are looking to measure the ‘period’ of the waveform, which is the time interval between successive cycles. In your top photo, you can measure the period as the time between the trailing edges of two consecutive pulses.

If you took that photo with the scope set-up as in your last photo, with time per division equal to 5uS, then the period is 10 divisions so at 50us is far too slow.

So switch the scope to the 1us/div range and speed up your oscillator until the period equals 5 vertical divisions of the graticule.

[savetheday]

I did every thing and i guess it's working now.But i checked with 3 ohm resister it reads something like 27.8 or 32 And with 10 ohm resister 10.4
It's not bad.I'm going to use like that.
Thanks a lot
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[savetheday]

and those.