EEVblog Electronics Community Forum

Electronics => Repair => Topic started by: elmezie on January 16, 2017, 06:02:45 am

Title: UCurrent Gold
Post by: elmezie on January 16, 2017, 06:02:45 am
Hello,

Is it possible to fix a blown resistor on the Ucurrent Gold? I can no longer get accurate values on the 1mv/ua setting?
I applied too much current while in that switch position and think I blew the resistor?


Thanks in advance for any information.
Title: Re: UCurrent Gold
Post by: tautech on January 19, 2017, 05:37:26 pm
Hello,

Is it possible to fix a blown resistor on the Ucurrent Gold? I can no longer get accurate values on the 1mv/ua setting?
I applied too much current while in that switch position and think I blew the resistor?


Thanks in advance for any information.
Welcome to the forum.

Try this link and links within for the schematic and other info:
https://www.eevblog.com/projects/ucurrent/ (https://www.eevblog.com/projects/ucurrent/)
Title: Re: UCurrent Gold
Post by: LA7SJA on January 19, 2017, 11:51:04 pm
Take your most accurate ohm meter an measure on the ucurrent input in the mv/uA setting, it should read 10 KOhm (R2) (But if r2 has burn due to high current >0.1W in 10K what was the voltage and what else was destroyed). I have two fast lo capacitance diodes back to back over the input to prevent burning out the shunt resistors when I f... up.

Johan-Fredrik
Title: Re: UCurrent Gold
Post by: JDW on March 29, 2017, 09:02:46 am
I have two fast lo capacitance diodes back to back over the input to prevent burning out the shunt resistors when I f... up.

Can you post a schematic of where your diodes are located and also link the datasheet for us?

By the way, if the addition of those 2 diodes prevents shunt burn-outs without adversely affecting precision of the uCurrent Gold, why were they not included in the original design?  For truly, it is mentioned that the circuit was not "fused" at all in order to obtain the best precision possible.

Thanks.