ELEKTOR FORUMS

Hi all

I just finished building the ESR/C meter (Sept 2005) and have noticed that
the bottom end of R26 (10K) is shown on the circuit diagram as connected to
the Cx - terminal but it seems to be connected to the Cx + terminal by
tracing the PCB connections.

Also Op-Amp IC7 (LF412) positive rail is permanantly connected to the battery
and not switched of via the on/off switch. Is there a reason for this?
Does it make any difference if I've linked the S2 position on the PCB and put
the power switch in the battery supply lead.

In Capacitance mode when I try to measure capacitance above about 470uF the
display briefly flashes "ESR DC" (i.e. looks like the meter is going into
ESR mode) and then the message "Capacity Zero Setpoint Error" is displayed.
At this point the meter has to be switched off and back on in order to make
more measurements. Capacitors below about 470uF can be read ok and ESR mode
seems to be operating correctly as well.

One thing I did notice was that setting the 40mV offset for the Op-Amp (IC7)
is quite difficult as it jumps between 29 to 43mV regularly.

Anyone any ideas?

Many thanks

Leslie

Hola colega, la razón por la cual el punto B+ de la batería esta conectado directamente con la alimentación del OP LF 412 solamente es para que sea posible realizar la calibración de la tensión de Offset a 40Mv, ya que en este momento no esta presente la señal de 200Kz en la llave HC4066, ya que estando presente esta señal se hace imposible la calibración correctamente.

Con respecto a la parte de capacidad el error que tu dices que aparece en el display, puede deberse, por lo menos en mi caso ocurrió asi, tenia mal cableada la llave de conmutación ESR/Capacimetro, revisa las conexiones.

En mi caso tambien se me a echo dificultoso el ajuste de los 40Mv en la pata 7 del OP LF412, no puedo entender aun a que se debe esto, a mi tambien me varia entre 30 y 50 mv.
Si alguien sabe cual puede ser el problema agradeceríamos la ayuda.

Attention:
Gabriel Beguiriztain
Argentina

Hello Lopb, first check this.

In addition to a hex file with the executable program a PIC also needs a set of configuration codes. These codes may be contained in the hex file, however PIC programmers deal with them in different ways. Here are the settings:

040259-41 PIC16F877:
Code Protection________________Off
In-Circuit Debugger____________Disable
FLASH Program Write____________Enable
Data EE Memory Code Protection_Off
Low Voltage Programming________Disable
Brown Out Reset________________Enable
Power-Up Timer_________________Enable
Watchdog Timer_________________Enable
Oscillator_____________________HighSpeed oscillator

Configuration word is 3F72.

040259-42 PIC16F84:
Program Memory Code Protection_Off
Power-Up Timer_________________Enable
Watchdog Timer_________________Disable
Oscillator_____________________HighSpeed Oscillator

Configuration word is 3FF2.


The Microcontrollers, only PIC16F84-20P and PIC16F877-20P

Best Regards.
Gabriel
Argentina