How to measure a ziner impedence accurately

[Muhammad Faheem Arshad]

I am using SMAZ30. due to heating i cant measure its impedence accurately. Please reply along with circuit diagram if possible

[dagakshay]

hey muhammad,

can you explain what is SMAZ30… and how to use it…

[Muhammad Faheem Arshad]

i am using Zener Diode SMAZ30 and i am measuring its impedence at test current 25 mA. The impedence should be less then 15  ohm but every time i am getting a higher impedence because zener heats up too much.

I tried to turn off power supply very rapidly to avoid heating but the minimum value i got through was 35 ohm.  

The method i used is zener diode and a resistor of 1K in series. I took 2 zener voltage values 1 at 26 mA and the 2nd at 24 mA and then used the following formula.

 

       Zzt = Vz@26mA-Vz@24mA

                     26mA-24mA

 

Do you know any good method to measure its impedence ????

[dagakshay]

can you past your ckt you are using?

by using ADC you can do that but still i want to see that circuit once. then only i can say some thing…

by the way, why you want to mesure its impedance?

[Muhammad Faheem Arshad]

This is the ckt i am using for measuring zener impedence along with the above formula. I am testing its impedence as one of my project. Can you plz help me to find any other method to measure its impedence less then 15 ohm (in datasheet). The problem which i think is only heating problem it heats ups so rapidly that its impedence increases wysiwyg_imageupload:1068:

[dagakshay]

hello Muhammad,

you have use zener in reverse baise but in your case here it will work as a simple diode you must connect that in parallel combination with your ckt. here the zener is getting heated you might be because of increase in the reverse bais, same as if you connect a normal diode in reverse baise and you increase the reverse biase vlotage across it after a time it will start getting heated up and it might also damage the component.

wysiwyg_imageupload:1074:

here in above ckt D1 is the zener diode. you can conncet any ckt accroding your project i just pasted a simple logic here ( in the red box. but if you wont connect any ckt in red box then again the zener diode will get heated up as in you case.

 

nice efforts, let me know till where you have reached…

[Muhammad Faheem Arshad]

Thanxs for your reply…. I just tried your given ckt but unfortunately i got impedence of 750 ohm …. I took two Vz readings 1 at 26 mA and 2nd at 24 mA.

         17.42 V @ 26mA and 15.92 @ 24 mA

 

 

       ZzT=   17.42 V  -15.92   = 750 ohm

                    26mA-24mA

 

 

 

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